Subclinical hypothyroidism is a condition in which there is an increase in the level of pituitary hormones against the background of the normal concentration of thyroid hormones. Pathology is asymptomatic and is detected by chance during laboratory examination. Subclinical hypothyroidism is considered the initial stage of thyroid dysfunction and without treatment leads to the progression of the disease with the development of full clinical symptoms and adverse effects for the woman and the fetus.
Causes of the disease
Subclinical hypothyroidism occurs in 3-17% of people, and its prevalence is directly dependent on gender and age. The disease is more often diagnosed in women. The likelihood of hypofunction of the thyroid gland increases with age. The peak occurs at 60-75 years, however, in the reproductive period, the disease may develop. Often subclinical hypothyroidism is detected by chance with a comprehensive examination during pregnancy.
There are the following causes of the disease:
- Reducing the amount of functional tissue of the thyroid gland (chronic autoimmune thyroiditis, the effects of ionizing radiation, etc.).
- Violation of the synthesis of thyroid hormones on the background of iodine deficiency and other factors.
- Pathology of the pituitary and hypothalamus, in which the production of thyroid hormones decreases.
The probability of development of subclinical and further manifest hypothyroidism increases when a woman lives in iodine-deficient regions, when the intake of this important element with food is disturbed. In Russia, iodine deficiency is noted in all regions remote from the sea coast.
Pregnancy is not a risk factor for hypothyroidism. On the contrary, while waiting for the baby, the opposite state arises - transient hyperthyroidism. The synthesis of thyroid hormones increases to meet the needs of the fetus, the concentration of T4 and T3 in the blood rises. The growth of thyroid hormones is observed in the first half of pregnancy. This condition is considered completely normal and does not require treatment.
The concept of "subclinical hypothyroidism" implies a complete absence of symptoms. A pregnant woman feels good and does not notice the manifestations of the disease. In the initial stages of its development, the hypofunction of the thyroid gland has virtually no effect on the functioning of the internal organs and nervous system of the woman.
Numerous studies on the problem of subclinical hypothyroidism indicate that in some cases the disease is accompanied by minimal symptoms. The woman herself can not pay attention to them, writing off the usual discomfort during pregnancy, and only a careful questioning of the patient helps the doctor to understand the situation.
Signs of subclinical hypothyroidism:
- Increased anxiety, a tendency to depression.
- Decreased attention and memory, difficulty in building logical chains and decision making.
- Unmotivated weakness, fatigue, loss of strength.
If these symptoms appear, it is useful to undergo a minimal examination by an endocrinologist and exclude the pathology of the thyroid gland.
Pregnancy complications and consequences for the fetus
Despite the absence of overt symptomatology, subclinical hypothyroidism requires mandatory treatment. Dysfunction of the thyroid gland in the mother can lead to the development of congenital hypothyroidism in the fetus. Problems arise even with minimal changes on the part of the organ, not to mention the manifestation of the disease.
The development of the thyroid gland of the fetus in the first weeks of pregnancy is exclusively under the influence of maternal hormones. The lack of T3 and T4 in the first trimester leads to irreversible consequences for the child. The appearance of severe congenital defects of the nervous system, mental retardation. This condition is practically not amenable to drug therapy. Numerous studies show that children from women with untreated subclinical hypothyroidism do not adapt well to changing conditions of existence and have worse Apgar scores compared to babies whose mothers took levothyroxine during pregnancy.
Other complications of gestation:
- Spontaneous miscarriage (mostly for up to 8 weeks).
- Vaginal bleeding at any stage of pregnancy.
- High risk of preterm delivery.
- Detachment normally located placenta.
- Placental insufficiency and hypoxia.
- Bleeding during childbirth.
- Fetal death of the fetus.
Subclinical hypothyroidism creates problems even at the stage of conceiving a child. With such a diagnosis, not all women manage to become pregnant. The hypofunction of the thyroid gland interferes with the normal maturation of the follicles and full ovulation, which prevents the conception of a child. It has been observed that in vitro fertilization against the background of subclinical hypothyroidism also often fails. For this reason, gynecologists recommend that all women who are planning a pregnancy be preliminarily examined for thyroid pathology and receive treatment if necessary.
Modern laboratory diagnosis of subclinical hypothyroidism during pregnancy or at the stage of conceiving a child involves the determination of two indicators. Normal values of hormones depending on the period of gestation are presented in the table.
- An increase in TSH with a normal T4 value indicates subclinical hypothyroidism.
- The manifest form of the disease is accompanied by an increase in both TTT and T4.
The definition of T3 - another thyroid hormone - as a screening is not justified. With a normal value of T4, the level of T3 is virtually unchanged. A decrease in T3 is noted in severe course of the manifest form of the disease and gives an unfavorable prognosis.
- Priority in the diagnosis of subclinical hypothyroidism is given to thyroid stimulating hormone (TSH). It is this substance that reacts first to changes in the body.
- Hypofunction of the thyroid gland may be transient with medication or after severe illness. If there is doubt, a repeated determination of TSH and T4 is required after 3 months.
- If autoimmune thyroiditis is suspected, a determination of the level of antibodies to thyroid peroxidase (AT-TPO) is shown. The normal value of this indicator is less than 5.6 U / ml regardless of the gestational age.
In subclinical hypothyroidism, there is a slight metabolic disorder and abnormalities in the heart and blood vessels. If pathology is detected, the following are additionally assigned:
- Biochemical analysis of blood with the assessment of lipid metabolism.
- Ultrasound of the thyroid gland.
To monitor the condition of the fetus, an ultrasound study with Doppler, cardiotocography is performed.
Principles of treatment
Subclinical hypothyroidism, despite the complete absence of complaints from women, requires the mandatory appointment of hormonal drugs. Denial of therapy threatens the progression of the disease and the development of severe complications for the fetus.
For the treatment of subclinical hypothyroidism in pregnant women, levothyroxine is prescribed. The dosage of the drug is calculated by the doctor individually for each patient based on the needs of the body, the level of TSH and the duration of pregnancy. Approximate initial dose - 2.3 mcg / kg. The dosage of medication may be revised during pregnancy and after childbirth. If a woman took levothyroxine before conceiving a child, its dosage is increased by 50%.
Levothyroxine sodium is prescribed in tablets. Pharmacies have a large selection of the drug in various dosages - from 25 to 150 mg. The entire daily dose must be taken once, preferably in the morning.
The drug is taken under the constant control of hormone levels (TSH and T4). If the dose of levothyroxine was chosen correctly, TSH should not fall below 2 IU / ml, T4 should remain at the upper limit of normal. The first blood test should be conducted no earlier than 14-28 days. In the future, the assessment of hormone levels is shown every 8-12 weeks.
All pregnant women are additionally prescribed iodine preparations at a dosage of 200 mg per day. Iodine can be a part of multivitamin complexes. If vitamins for pregnant women contain a sufficient dosage of iodine, it is not necessary to take it separately.
Births with subclinical hypothyroidism are conducted through the natural birth canal in satisfactory condition of the woman and fetus and in the absence of complications of the underlying disease.
Subclinical hypothyroidism is a serious condition that requires mandatory medical supervision. The cunning of the disease lies in the fact that the woman feels healthy, and therefore does not turn to the doctor for help. For this reason, all expectant mothers living in iodine-deficient regions need to undergo screening tests for thyroid pathology - donate blood for TSH and T4. The analysis is best done before conceiving a child or in the first weeks of pregnancy. If hypothyroidism is detected, hormone replacement therapy and observation up to the birth is shown.
Symptoms and causes of hypothyroidism during pregnancy
Subclinical hypothyroidism is cunning because pathology may have erased (not pronounced) symptoms or be absent altogether. During gestation, the woman’s general health is changing, so some negative changes in the body are attributed to pregnancy.
The symptomatology of a subclinical hypothyroidism is various and ambiguous.
Most often, patients complain of:
- state of apathy,
- increased drowsiness,
- soreness of joints (especially of the hands),
- systematic nausea without vomiting,
- swelling of soft tissue
- hair loss and brittleness
- weight gain
- prolonged constipation.
Symptoms do not appear all at once, such as signs of toxicosis during pregnancy, but gradually. Therefore, you need to carefully monitor the slightest changes in the body.
The main reason for the development of the disease lies in the lack of hormones that are produced by the thyroid gland. This situation may occur in the following cases:
- Surgical intervention on the thyroid gland (partial or complete removal).
- The presence of tumors or other nodal structures in the thyroid gland.
- The presence of inflammation in the gland.
- Iron was exposed to ionizing radiation.
- Iodine deficiency in the body.
- Genetic predisposition.
- Violations in the functional work of the pituitary gland.
During pregnancy, the load on the thyroid gland increases, and if there is a pathology of this organ, then this is a real test for the endocrine system. Autoimmune thyroiditis and pregnancy - consider how dangerous the disease is for the mother and fetus.
TSH when planning pregnancy - indicators of norms and deviations, see here.
The amount of thyroid-producing hormone produced during pregnancy varies. This article http://gormonexpert.ru/zhelezy-vnutrennej-sekrecii/shhitovidnaya-zheleza/norma-ttg-pri-beremennosti.html presents the normal indicators of the amount of thyreotropin by trimesters.
Danger to the fetus
Hormone deficiency adversely affects the body of the unborn child. First of all, his nervous system suffers.
In the absence of adequate hormonal therapy, the risk of developing mental and neurological diseases in a child is high.
Often there is intrauterine growth retardation. As a result, the child is born with a small weight. Possible pathology of the development of any organs and systems of the fetus. Often a child is born with a congenital form of hypothyroidism, so he will need to constantly receive the hormone artificially throughout his life.
Subclinical hypothyroidism does not manifest itself as pronounced unpleasant symptoms, but it is unacceptable to leave it without treatment! Unforeseen can happen at any time. In addition, the subclinical form of the disease in the absence of treatment often turns into manifest, which requires a different, more serious treatment.
The test for TSH during pregnancy must be given in the first trimester. Sometimes there is an increased rate of this hormone. TSH elevated during pregnancy - how dangerous is it?
On the causes of low TSH during pregnancy, read this link. What to do if the result is below the norm?
The conditions in which the female body falls into hypothyroidism in the thyroid gland are called primary in medicine textbooks. A decrease in the hormonal level depends on the specific reasons. They are different for each individual person. The most common causes lie within the thyroid itself (99%), or in other organs (1%).
Other systems affecting the thyroid gland - the pituitary gland, the hypothalamus.
- primary level - the defeat of glandula thyroidea,
- secondary - pathologies of the pituitary gland,
- tertiary — hypothalamus.
The list of grounds and factors causing primary hypothyroidism during pregnancy include:
- abnormal deviations of the thyroid gland from the norm,
- iodine deficiency,
- two types of thyroiditis: autoimmune, postpartum,
- treatment with radioactive iodine,
- therapy using irradiation of the affected part of the gland,
- congenital form
- reception for a long period of funds containing iodum,
- cancer pathology.
Description of the clinical picture
Statistics exposes the distribution of pathology among women. Approximately 19 cases per thousand women. The percentage is quite high, but there is no way to reduce its performance. The disease does not give bright signs. In the early stages, the symptoms are hidden, not specific to any health abnormalities associated with the thyroid. Patients become quickly tired, so they explain fatigue with gestation. Pregnancy with hypothyroidism is rare, doctors give this medical interpretation. Hypothyroidism leads to infertility. Only 2% of pregnant women are diagnosed with the disease.
The clinical picture of the course of the disease is characterized by numerous symptoms: decreased activity in work, weakness, overwork, frequent depression, memory loss, attention abundance, deterioration of mental abilities and capabilities, excessive fullness, dry skin, hair loss, changes in voice, edema, constipation.
Hypothyroidism affects all internal processes. There is a slowdown, it is associated with a decrease in the amount of hormones, their lack of thyroid. Patients become susceptible to infectious diseases, reduced immunity. Weakness begins to affect the body even in the morning after a long night of rest. Patients feel pain in the head, muscles, joints. Hands are numb, skin swells, nails break, hair split.
Mental retardation becomes especially dangerous.
It leads to serious consequences such as:
- Ischemic disease
- Cardiovascular insufficiency.
Patients with hyperthyroidism acquire lameness. Women observe frustration in menstrual cycles. Monthly become longer and more abundant. It happens and the situation is opposite to this: the menstrual cycles completely disappear. Severe lesions include heart disease. They come from slowing heart rate, increasing cholesterol.
Complications for fetal development
Pathological defeat of the thyroid gland during gestation is dangerous for the future baby. It disrupts the developing central nervous system, leading to terrible brain damage. The disease affects the formation of the thyroid gland (glandula thyroidea) of a child. In the first trimester, the embryo develops with maternal care, female hormones. The second half of the pregnancy period is complicated. Hypothyroidism in pregnant women intensifies the transfer of transplacental hormones T4. Protein is trying to compensate for the lack of hormonal compounds of the developing fetus. Experts diagnose congenital hypothyroidism. It begins to eliminate with the help of complex replacement therapy.
Deficit of hormones leads to irreversible pathological processes in the child’s body, affecting the central nervous system and the brain.
A woman entering a gestation period must visit a gynecologist and an endocrinologist. Together they will create conditions for a safe forecast for both maternal health and the baby. To date, hypothyroidism during pregnancy occurs infrequently.
Laboratory diagnostics and medical sources use two terms for the disease:
- Subclinical hyperthyroidism.
Subclinical hypothyroidism during pregnancy is characterized by the following indicators:
- Increases the level of TSH.
- The hormonal thyroglobulin formations are isolated.
- T4 has a normal free level.
The manifest view has other characteristics:
- TSH increased.
- Hormonal background T4 reduced.
Any abnormalities in the thyroid lead to threats. Most of the dangers threatens the child.
The effect of the disease on the body of a pregnant
Gestational hypothyroidism at a certain period entails pathology:
- disruption of normal brain formation,
- differentiation, myelination of neurons,
- hormones migration
The gestational period increases the risk of miscarriage and premature termination of pregnancy, possibly the birth of a dead fetus. При удачном завершении ребенок долго остается в опасности неправильного развития.He continues to develop complex violations of internal systems.
Endemic cretinism of the neurological type is manifested in the form of:
- mental retardation,
- deafness and dumbness
- spastic diplegia,
Endemic cretinism of myxedematous nature leads to thyroid abnormalities, dwarfism.
A study of the symptoms and condition of the fetus is required for any signs of illness in the mother. Specialists will monitor the entire clinical picture of the development of the fetus and the condition of the woman, give the necessary explanations, create the necessary conditions for the mother and child.
Treatment methods during pregnancy
The goal of treatment is to restore the hormonal level characteristic of a healthy organ. Non-drug treatment is not used, as well as surgery. The only method is medications. An endocrinologist selects a dose of levothyroxine sodium. The admission rate is selected by the doctor to keep the content of thyroglobulin in the blood according to established standards. Medical sources give accurate figures of the amount and balance of hormones. Overdose leads to damage to the functions of the pituitary gland, if overdose occurred after the birth of the baby, it worsens lactation.
Replacement therapy during fetal development
The disease can not be the cause of failure of pregnancy planning. Specialists offer one method of therapeutic effects on symptoms - replacement therapy with thyroid hormones.
Doctors spend the compensation of thyroxine, examine its level every 8 weeks.
Dose of medication varies from fetal development:
- 1 trimester - increasing the dose,
- 20-22 week - enhanced reception of L-thyroxine,
- The last trimester is a normal technique.
L-thyroxin is offered at pharmacy kiosks in the form of tablets. The mass of the drug is 50 or 100 µg of the substance in one pill. Replacement therapy will be long, most often it will have to adhere to throughout life.
Any woman who wants to become a mother should be examined by a gynecologist, consult an endocrinologist. These visits to doctors will guarantee the preservation of the fetus, confidence in the state of their health. Hypothyroidism and pregnancy require timeliness at the beginning of treatment, which is possible only after all diagnostic procedures have been performed.
To increase the activity of the thyroid gland contributes to the reception of herbal, which include St. John's wort, chamomile, birch buds, mountain ash, coltsfoot.
Doctors do not recommend to take decoctions on the basis of Hypericum during pregnancy, as this medicinal plant contains substances that increase the tone of the uterus. Also, iodized and beetroot spirit tinctures, which are used to treat subclinical hypothyroidism, are contraindicated in pregnant women.
When deciding to be treated by folk methods, a woman must consult with an endocrinologist and a gynecologist without fail, since the uncontrolled use of medicinal decoctions and self-treatment with iodine-containing drugs during pregnancy can do more harm than good.
Prevention of subclinical hypothyroidism in pregnant women
To prevent the disease from developing during pregnancy due to iodine deficiency, a prophylactic course with the introduction of physiological dosages of iodine-containing drugs into the body is recommended.
Medicines are prescribed for confirmed iodine deficiency.
Self-administration of such drugs can cause a surplus of iodine, fraught with the development of hyperthyroidism, no less dangerous during pregnancy than insufficient functionality of the organ.
As part of the prevention of gestation complicated by subclinical hypothyroidism, all women with this diagnosis at the planning stage of pregnancy are prescribed levothyroxine sodium, regardless of whether the level of TSH is elevated or not.
Implications for the child
In the first half of pregnancy, the central nervous system of the fetus is laid. Its formation occurs at the expense of the mother's thyroid hormones, since the thyroid gland of the fetus does not function during this period.
Complications of hypothyroidism, not timely corrected in a pregnant woman, include:
- congenital malformations
- hypofunction of the thyroid gland,
- fetal death of the fetus,
- mental retardation
- lack of body weight at birth.
Congenital hypothyroidism in a newborn who has undergone hypothyroxinemia intrauterinely, which occurs due to inadequate treatment of subclinical hypothyroidism during pregnancy in a woman, leads to irreversible disturbances in the central nervous system of the child.
TSH rates during pregnancy
First of all, we will discuss the concept of the TSH norm for pregnant women. Differences from the general population are due to physiological changes in thyroid function during pregnancy.
The penetration of thyroid hormones through the placenta to the fetus, an increase in the concentration of thyroid binding
globulin, accompanied by increased binding of hormones, and their increased disintegration in the placenta under the influence of type 3 deiodinase dictate an increase in the synthesis of thyroid hormones in a woman's body. For enhanced synthesis of hormones, it is necessary that the thyroid gland has enough functional reserves and there is no iodine deficiency. An additional stimulus for increasing the functional activity of the thyroid gland in the first trimester of pregnancy is the placental hormone - human chorionic gonadotropin (hCG), a TSH agonist, capable of interacting with its receptors. At about the 8th week, at the peak of the secretion of hCG, the synthesis of thyroid hormones increases, which suppress the production of TSH by the negative feedback mechanism, so that for the first trimester a decrease in TSH is typical, sometimes below normal. At the end of the first trimester, as the hCG decreases, the level of TSH is restored to its original values .
Studies have shown that the level of TSH and free T4but not free T3, statistically significant changes in different periods of pregnancy, with the minimum level of TSH observed at the beginning of pregnancy, and the minimum level of free T4 - at the end of pregnancy .
Normal levels of thyroid hormones are important both for a pregnant woman and for the fetus, especially in the first trimester, when the fetal own thyroid gland is not yet functioning. Taking into account the physiological changes in thyroid function during pregnancy and the importance of maintaining normal levels of thyroid hormones for proper formation and growth of the fetus, it is necessary to clearly define the concept of a norm for a pregnant woman, and this rate should be maintained throughout pregnancy. In addition, it is necessary to evaluate the justification of medical interventions during pregnancy, taking into account not only the health of the woman, but also the health of her unborn child.
Since 2011, in our country, as in many other countries, trimester-specific TSH standards recommended by the American Thyroid Association (ATA) have been used: for the first trimester 0.1–2.5 mU / l, for the second trimester - 0.2– 3.0 mU / l and for the third trimester - 0.3–3.0 mU / l. It should be noted that in the ATA recommendations, these standards were proposed only for laboratories that for some reason do not have their own established standards. Recommended reference intervals of TSH were based on the results of six cohort studies conducted in the United States and some European countries, in which it was shown that in the first trimester the level of TSH in pregnant women is significantly lower than in the second and third trimesters .
However, the use of such a rule has led in many countries to a very high prevalence of subclinical hypothyroidism. So, when using the upper limit of TSH for the first trimester of 2.5 mU / l in one study conducted in China, subclinical hypothyroidism was detected in 27.8% of pregnant women, in some regions of Spain 37%, and in the Czech Republic in 21 % [4–6].
In this regard, in many countries of Asia and Europe, studies have been conducted to determine their own standards of TSH. When summarizing the data of these studies, it was shown that the level of TSH in pregnant women without thyroid gland pathology living in different regions is significantly different. In the first trimester, the upper limit of normal levels of TSH is in the range from 2.15 to 4.68 mU / l. With the use of regional TSH rates, the frequency of hypothyroidism decreased significantly and averaged about 4% [7, 8].
It should be noted that a higher than 2.5–3.0 mU / l, upper limit of the TSH rate was found not only in Asian countries such as India, South Korea, China [4, 9], but also in some countries Europe, for example, the Netherlands, Czech Republic, Spain [10–12]. These differences may be due to ethnic characteristics, as well as the iodine availability of the region in which the study is being conducted, and the prevalence of a carrier of antithyroid antibodies .
Given the accumulated data, ATA recommendations came out in 2017 with some changes. It is still preferable to use the TSH norm for pregnant women defined in this population, taking into account their place of residence. But if such norms cannot be determined for any reason, then it is recommended to use reference values commonly used in this population . However, in this case, physiological changes in TSH are not taken into account, especially in the first trimester of pregnancy. In a study conducted in the Netherlands, it was shown that when using the general population standards of TSH it is impossible to identify all pregnant women with reduced thyroid function in time, which affects the outcome of pregnancy . In this regard, it is advisable to reduce the commonly used upper limit of the TSH rate by 0.5 mU / l, which is also taken into account in the latter recommendation of the ATA .
Thus, taking into account the accumulated data and the latest recommendations of the ATA, it is currently recommended to use either the norms for pregnant women defined in this ethnic group, taking into account the region of residence, or the commonly used population norms with a reduced upper limit of 0.5 mU / l.
Unfortunately, in Russia there are currently no national clinical guidelines for the diagnosis and treatment of thyroid disease during pregnancy. In this situation, every doctor is based on information resources available to him. In Tironet.ru, a well-known in Russia and highly popular among physicians, clinical recommendations based on the previous version of ATA recommendations, the level of TSH is 95 percentile in early pregnancy, although TSH> 95 percentile combines subclinical and manifest hypothyroidism, which may affect the results of the study .
The risks of spontaneous abortion increase with a combination of elevated TSH and high titer of antibodies to thyroperoxidase (TPO). In a study by C. Lopez-Tinoco et al.  it was demonstrated that the presence of antibodies to TPO in pregnant women with subclinical hypothyroidism increases the risk of abortion by more than 10 times. Similar data were obtained by researchers from China. The highest risk of miscarriage was identified in the group of pregnant women with subclinical hypothyroidism (TSH 5–10 mU / l) and elevated titer of antibodies to TPO (odds ratio (OR) 9.56, p 2.5 mU / l and high titer of antithyroid antibodies.
However, not all studies confirmed the negative effect of TSH> 2.5 mU / l on the course of pregnancy. Thus, in the study of H. Liu , statistically significant differences in the frequency of termination of pregnancy in the groups of pregnant women with a TSH of 2.5 mU / l pregnant women underwent replacement therapy with levothyroxine. In the universal screening group, hypothyroidism was found more often (OR 3.15) and pharmacotherapy was prescribed more often, but, despite the best detection of hypothyroidism in the total screening group, differences in pregnancy complications and outcomes were not detected. The authors concluded that total screening does not improve pregnancy outcomes . However, the influence of mass in this study cannot be excluded, since healthy pregnant women significantly exceeded the number of hypothyroid patients in both groups.
Conflicting data were obtained in the study of the association of subclinical hypothyroidism and preterm labor. In a study by Casey et al.  revealed a link between subclinical hypothyroidism and labor before 34 weeks. gestation, but at the same time such a relationship was not found for periods of less than 32 or less than 36 weeks. Further on, similar studies were obtained in similar studies, partly due to the association of pregnant women with subclinical and manifest hypothyroidism into one group, as well as the inclusion of pregnant women with antithyroid antibodies in the study.
As shown by T. Korevaar et al. , the complicated course of pregnancy depends on the degree of increase in TSH. Pregnant women were divided into groups depending on the level of TSH: 2.5–4.0 mU / l or more than 4.0 mU / l. At TSH below 4.0 mU / l, no increase in the frequency of preterm labor was detected, while at TSH> 4.0 mU / l, the risk of childbirth was earlier than 37 weeks. increased 1.9 times, and previously 34 weeks. - 2.5 times. But the primary analysis was carried out without taking into account the antibody titer to TPO. With the exclusion from the analysis of pregnant women with elevated antibodies to TPO, the difference between the groups disappeared, and even an isolated increase in TSH> 4 mU / l did not affect the frequency of preterm birth. This study once again demonstrated the importance of distinguishing between pregnant women and normal and elevated antibody titers to TPO, since they are an independent risk factor for complicated pregnancy.
The impact of subclinical hypothyroidism on the development of pregnancy-related hypertension and preeclampsia is currently questionable. Earlier, in cohort studies, an association of subclinical hypothyroidism and preeclampsia was detected, but only if screening for hypothyroidism was performed in late pregnancy. If the function of the thyroid gland was studied before 20 weeks. pregnancy, no dependence was detected [26, 27]. It is assumed that in the initial stages of preeclampsia development, the placenta can produce factors that affect the function of the thyroid gland . With elevated TSH (> 2.15 mU / l), in the first trimester of pregnancy, there was no increase in the frequency of pregnancy complications, including pre-eclampsia, developing after 20 weeks. .
When studying moderately elevated TSH, from 2.5 mU / l to 97.5 percentiles, and the population norm, an increase in the frequency of pre-eclampsia was found only in pregnant women with highly normal free T4, the remaining highly normal level of TSH did not affect the frequency of pre-eclampsia . However, in some studies, an association between elevated TSH and elevated blood pressure during pregnancy was found. For example, in the study of L. M. Chen  an increased risk of gestational hypertension was detected, as well as a small body weight of the fetus in pregnant women with subclinical hypothyroidism. That is, at first glance, diametrically opposite results were obtained. But in this study, subclinical hypothyroidism was diagnosed with TSH> 3.47 mU / l, which was defined as the upper limit of normal in this laboratory, which is significantly higher than 2.5 mU / l. Probably the level of TSH used to diagnose subclinical hypothyroidism affects the results of a study of its effect on the course of pregnancy.
Usually, with conflicting data, a meta-analysis method is used to identify the truth. A recent meta-analysis of 18 cohort studies showed that subclinical hypothyroidism is associated with several adverse pregnancy outcomes, such as miscarriage (OR 2.01, 95% confidence interval (CI) 1.6–2.44), placental insufficiency (OR 2.14 , 95% CI 1.23–3.7) and increased neonatal mortality (OR 2.58, 95% CI 1.41–4.73). Associations with other adverse outcomes, such as preeclampsia, have not been identified . It should be noted that the studies included in the meta-analysis used different threshold values of TSH for the diagnosis of subclinical hypothyroidism. Only in 6 out of 18 studies the threshold value of TSH was a level of 2.15–2.5 mU / l. Moreover, three studies included pregnant women with a TSH> 2.5 mU / L and a normal level of free T4. That is, the degree of increase in TSH could be different, from 2.5 to 10 mU / l. And as we can see from other studies, varying degrees of increase in TSH have different effects on pregnancy outcomes. In most studies of meta-analysis, subclinical hypothyroidism was diagnosed with TSH> 3.5 mU / L. And this is the currently recommended upper limit of the TSH norm for pregnant women, if modified general population norms are used.
Effects of TSH from 2.5 to 4 mU / l on the neuropsychiatric development of the fetus and other indicators of fetal health have not been identified [31, 32].
Considering the data obtained at present, it can be considered that TSH> 2.5 mU / L is associated with spontaneous abortion. Other adverse pregnancy outcomes are associated with a higher TSH threshold. Pregnant women with elevated TSH and antithyroid antibodies deserve special attention. In this case, the adverse effect on the course of pregnancy increases.
Но необходимо понимать, изменится ли ситуация к лучшему, если компенсировать функцию щитовидной железы при субклиническом гипотиреозе у беременных. Многие исследователи поддерживают идею лечения, т. к. оно довольно безопасно и может оказать положительное воздействие на вынашивание беременности . The outcomes of pregnancy in women taking levothyroxine sodium for manifest or subclinical (TSH> 2.5 mU / L) hypothyroidism, and euthyroid women did not differ. And this indicates the safety of treatment with levothyroxine sodium, at least with respect to pregnancy .
The administration of levothyroxine sodium to pregnant women with TSH above the norm determined in the local laboratory led to a total decrease in pregnancy complications. Moreover, the effect depended on the timing of the start of treatment and the time spent on reaching the target level of TSH.
The frequency of complications decreased if treatment started before 12 weeks. pregnancy and the goal of treatment was achieved in less than 4 weeks. .
In the study of S. Maraka et al.  it was shown that the prescription of substitution therapy for TSH of 2.5–5 mU / l reduces the risk of intrauterine growth retardation and a low score of the state of the fetus at birth on the Apgar scale. Other outcomes of pregnancy, including spontaneous abortion, were not found.
In other studies, the positive effect of treatment with levothyroxine was detected only in groups of pregnant women with TSH> 4.0–5.0 mU / L. At the same time, one study showed a significant reduction in the frequency of preterm labor (OR 0.38, 95% CI 0.15–0.98). In pregnant women with TSH 2.5–4.0 mU / l, prescribing replacement therapy did not improve pregnancy outcomes [36–38].
Thus, at present, the positive effect of replacement therapy with levothyroxine sodium at a TSH level of 2.5–4.0 mU / L, especially with a normal level of antithyroid antibodies, has not been proven. However, with a more pronounced increase in TSH, the positive effect of treatment is beyond doubt. It is possible that a positive effect is manifested only when using local norms of TSH, which increases the importance of their determination.
Based on the latest data, it can be concluded that during pregnancy, it is better to use local norms of TSH to make a decision about prescribing treatment with levothyroxine sodium. In the absence of local norms, either with TSH> 2.5 mU / l in pregnant women with antithyroid antibodies, or TSH> 3.5 mU / l in women without antibodies, the prescription of replacement therapy at least reduces the likelihood of spontaneous abortion, and possibly has other positive effects, especially if initiated in early pregnancy.
Subclinical hypothyroidism and fertility
An important question is what is the effect of subclinical hypothyroidism on the fertility of women. And this question raises two more: 1) at what level of TSH it is necessary to begin treatment when planning pregnancy
and 2) what is the target level of TSH at the pregnancy planning stage.
If a woman at the planning stage of pregnancy has identified a TSH of a more general population standard, the treatment is not in doubt. It is more difficult to resolve the issue of the need for treatment at a normal high level of TSH. Recently, there is increasing evidence of the effect of moderately elevated TSH on fertility. Indeed, it was found that in infertility in a woman the level of TSH is higher than in the control group, especially if the cause of infertility was ovarian dysfunction or the cause was unknown. . In one study, the administration of levothyroxine sodium to infertile women with TSH> 3 mU / l in 84.1% of women was accompanied by the onset of pregnancy, and in some women, spontaneous . But in earlier studies there was no association of increased TSH and reduced fertility in women . The revealed once increased level of TSH> 2.5 mU / l at the planning stage of pregnancy can independently decrease after the onset of pregnancy. One small study showed that in 50% of pregnant women with a TSH> 3 mU / l at the planning stage after the onset of pregnancy, the level of TSH independently returned to normal and became less than 2.5 mU / l. Unfortunately, this study did not examine the differences between the groups with elevated and normal levels of TSH after the onset of pregnancy .
In a larger study involving 482 women in vitro fertilization (IVF), the likelihood of
and save pregnancy depending on the original TSH. In 55% of pregnant women after pregnancy, TSH decreased from an initial level of 2.5–4.0 mU / l to 2.5 mU / l. The onset of pregnancy did not depend on the initial level of TSH. The authors concluded that treatment with an increase in TSH from 2.5 to 4.0 mU / l can be postponed until pregnancy, when this level is confirmed .
On the other hand, in a population study conducted in China, the dependence of the outcomes of a spontaneous pregnancy on the level of TSH, determined within 6 months, was revealed. before pregnancy. In women with TSH of 2.5–4.28 mU / l, compared with women with TSH below 2.5 mU / l (0.48–2.49 mU / l), an insignificant, but still statistically significant, increase in the frequency of spontaneous miscarriages (OR 1.1) and preterm labor
(OR 1.09). Heavier complications of pregnancy, such as perinatal mortality, fetal fetal death, cesarean section, were observed only at TSH levels> 4.0 mU / l .
Many studies have evaluated the effect of subclinical hypothyroidism and its treatment on the effectiveness of various assisted reproductive technologies (ART). Special attention to this group of women is explained by the use in the process of stimulation of high doses of estrogens, which can show compensated thyroid insufficiency. No negative effect of TSH levels from 2.5 to 4.9 mU / l on the results of insemination was detected. In one study, euthyroid women revealed an inverse association between the level of TSH at the time of pregnancy and the frequency of miscarriages . In another similar study, no association was found between an increased level of antithyroid antibodies and / or TSH> 2.5 mU / L per incidence of labor in women after insemination , although in a retrospective study, the performance of insemination increased when prescribing replacement therapy for women with TSH> 2 , 5 mU / l . IVF at TSH level 05/25/2018 Anxiety in the practice of a gynecologist. Glance ps.
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Insufficient hormone production
Lack of production of certain hormones by a woman’s body can significantly affect the condition of the fetus. The child as a result of such disorders can acquire inborn mental retardation, problems with the functioning of the nervous system, etc. Such disorders are dangerous for the health of the woman herself, since they can turn into sexual dysfunction or sterility. With a confirmed diagnosis of "hypothyroidism," conceiving a child is possible, but the expectant father and mother need to know what the consequences are in this case.
Is hypothyroidism dangerous during pregnancy?
The severity of thyroid abnormalities
As a rule, hypothyroidism is an independent (primary) disease that develops on the background of inflammation of the thyroid gland, or it can be triggered by impairments in the immune system.
Hypothalamic-pituitary phenomena become apparent in secondary hypothyroidism, which is caused by the action of infection or the appearance of tumors in the thyroid gland.
Subclinical hypothyroidism during pregnancy adversely affects the reproductive functions of the female body, reduces the possibility of conception. With this diagnosis, doctors often determine ovulatory infertility. In order to solve problems with conception and fetal development, women are advised to monitor their hormones and be attentive to the results of tests. If studies have identified these or other disorders in the functioning of the thyroid gland, it is necessary to apply the therapy prescribed by the doctor in order to normalize the production of hormones. These hormones are equally important for the health of both the expectant mother and baby. If the diagnosis of “subclinical hypothyroidism” was determined already during pregnancy, then the probability of spontaneous abortion will be high.
Consider how hypothyroidism occurs during pregnancy.
Course of pregnancy
If hypothyroidism has not been treated at all, the onset of pregnancy is very unlikely. However, if the pregnancy nevertheless occurred and triiodothyronin in sufficient quantities comes to the fetus before the 6th-8th week of its development, then at the subsequent stages of its development the iron of the unborn child begins independent work.
It is important to know that if during pregnancy there is no correction of iodine deficiency, then in the future there will be a high probability of irregularities in the development of the intellectual sphere of the newborn.
Studies conducted in America have shown that pregnancy with thyroid hypothyroidism runs smoothly in only two percent of women.
Mass screening of newborns for neonatal hypothyroidism makes it possible to learn about violations already on the 4-5th day (in prematurity - on the 7-14th day).
In iodine-deficient regions, women expecting a child are recommended to take iodine in the form of potassium iodide or as a component of multivitamin complexes. However, the dosage must be strictly calculated by the doctor, since an overabundance of the drug can lead to blocking the development of thyroid in the fetus.
Before planning a pregnancy, it is important to check if there are any abnormalities in the thyroid gland. In the very first weeks of pregnancy, the woman's body begins to produce an increased amount of TSH, as it will additionally be required for the fetus. Its maximum number is noted on the second day after birth. If the body of a pregnant woman does not feel the need for iodine, then the specified hormone will be produced in normal quantities.
But with iodine deficiency, the synthesis of this important hormone is significantly reduced, which is a negative indicator for the development of the future baby. Indeed, in the first trimester, the fetus is completely dependent on the hormones with which the maternal organism provides it. In case of their lack of child development, the appearance of pathologies is possible.
To minimize risks
In order to minimize the risks of pregnancy with thyroid hypothyroidism, therapy is prescribed by taking the hormone L-thyroxine. The dosage of the drug must be determined by the doctor, self-treatment in this case is absolutely contraindicated, since any violation of the hormone levels in the body is fraught with impaired development of the fetus. If a woman is undergoing this therapy, then she will need to donate blood for hormone level analysis throughout pregnancy every eight weeks. In the case of timely diagnosis and compliance with all treatment requirements, the prognosis is favorable. The drug can be finished only after delivery.
Causes of the disease
The main cause of hypothyroidism during pregnancy is the development of the pathology of the thyroid gland. Sometimes an illness can occur as a result of damage to the pituitary gland. Here are the most common causes of this disease:
- it can be a consequence of congenital pathology,
- may be caused by autoimmune thyroiditis,
- occurs as a result of iodine deficiency in the body,
- is a consequence of oncological processes
- develops due to tumors that appeared in the thyroid gland,
- is a consequence of irradiation of this gland,
- develops due to thyroidectomy.
How does hypothyroidism manifest during pregnancy?
Symptoms of subclinical hypothyroidism
In this disease, the symptoms are characterized by implicit severity. First of all, it can be psychological disorders flowing into the development of depression. Also in women suffering from this disease, decreased activity, lethargy. It is necessary to monitor these symptoms in order to timely diagnose. It is important to note such changes as irritability, inhibited speech, sluggish, inactive movements, mental depression, weight gain, malfunction of the cardiovascular system.
Subclinical hypothyroidism during pregnancy is manifested by high T3, while T4 is kept within the normal range. The clinical form is much more pronounced - it is characterized by an enlarged thyroid gland, swelling around the eyes, bradycardia (slow heartbeat), infertility and menstrual disorders, dry skin, chilliness, convulsions, constipation, pain and difficulty in swallowing. All this develops against the background of fatigue and depression.
To make a complete diagnosis, the patient is prescribed, in addition to tests for hormone levels in the blood, puncture of the thyroid gland.
Other symptoms that need attention
The organism with susceptible thyroid secretion is susceptible to infections. If they occur too often, attention should be paid to this. In addition, during pregnancy, the use of drugs that help to fight them is limited.
If a woman experiences constant fatigue from both mental and physical activity, this is also an alarming sign. At the loss of appetite, constant sleepiness and apathy, it is also necessary to pay close attention and identify their causes.
Also unsettled and too frequent mood swings, accompanied by indifference or aggression, are also a disturbing sign. In addition, in subclinical hypothyroidism, an organism is characterized by a slight increase in temperature, which may be accompanied by numbness of the extremities.
If you notice a change in voice - lowering its timbre, hoarseness (and, when examined, and swelling of the oral cavity), then this may be caused by a hormonal imbalance in the body. Another common sign of hypothyroidism is an increase in cholesterol in the blood, which is fraught with blockage of blood vessels. This can cause poor nutrition of the placenta.
The consequences of hypothyroidism during pregnancy are very serious.
How is the diagnosis?
A woman who needs to diagnose this disease must first receive a referral to laboratory tests, the results of which will help confirm the violation of thyroid hormone production. If this violation is confirmed, the beginning of pathological changes in the gland will be marked. Depending on the level of thyroid-stimulating hormone in the body, there will be either a deterioration of thyroid function or thyrotoxicosis.
If during pregnancy the disease is detected in a timely manner (at the beginning of the first trimester), then urgent therapy will be indicated for the pregnant woman. If the planning of conception revealed a compensated form of the disease, there will be no contraindications to pregnancy.
To reduce the effect of hypothyroidism on pregnancy, the doctor prescribes replacement therapy, which consists in taking L-thyroxine. However, this method of treatment does not exclude side effects. For example, women who are expecting a child may develop cardiovascular diseases, such as arrhythmia or tachycardia. Also, therapy may be accompanied by headaches or weight gain.
Planning a pregnancy and examining the organism of the future mother and father for various pathologies or diseases is a very important step, which is a manifestation of responsibility not only for their health, but also for the health and life of the future baby. Diseases identified in time are often treatable, or their harmful effects on the fetus will help negate replacement therapy. After all, hypothyroidism is a dangerous disease that can significantly impair the quality of life of a child.