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Hypothyroidism In Pregnancy: Causes Of This Complication Common In Pregnant Women

Warning Signs Of Hypothyroidism Common In Pregnant Women

The thyroid gland's function is significantly influenced by pregnancy. Hypothyroidism in pregnancy is a very common illness that can be treated.

Written by Editorial Team |Updated : February 8, 2022 11:18 AM IST

Thyroid hormones T3 and T4 regulate metabolism, consumption, and storage of energy. An underactive thyroid, often known as hypothyroidism, occurs when the thyroid does not produce enough thyroid hormone and is uncommon during pregnancy. The thyroid gland, positioned in the front of the neck, produces a variety of hormones that alter dramatically throughout pregnancy and are essential not only for a pregnant woman but also for her baby's development. High blood pressure, anaemia, muscle soreness, and weakness can all harm pregnant women and their babies if left unmanaged. Miscarriage, preterm birth, and even stillbirth are all possible outcomes. As a result, thyroid issues can sometimes begin or worsen during pregnancy or after childbirth.

Understanding Hypothyroidism During Pregnancy

Pregnancy has a significant impact on the functioning of the thyroid gland. The thyroid hormones are triiodothyronine and thyroxine TSH is the hormone manufactured by the pituitary which ensures the right amount of thyroid hormones are produced by the thyroid gland. The production of these hormones needs adequate amounts of certain amino acids and iodine besides the balance between the hormones of the brain what is called the hypothalamic-pituitary-thyroid axis. The thyroid gland in pregnancy specifically helps in positive structural changes in the fetal brain. Hypothyroidism refers to decreased functioning of the thyroid gland. Children whose mothers were severely iodine-deficient causing hypothyroidism during pregnancy may exhibit cretinism characterized by profound intellectual impairment deaf-mutism and rigidity of muscles.

In a normal pregnancy, there is an increase in iodine excretion and an increase in thyroid hormone production. All these factors influence thyroid function tests in pregnancy. The healthy thyroid adapts to these alterations through a change in thyroid metabolism iodine uptake and by impulses from the brain. Hence thyroid function tests of healthy pregnant women, therefore, differ from those of healthy non-pregnant women. There is a downward shift of the TSH reference range in pregnancy and hence the normal reference range in pregnancy is far lower than in nonpregnancy. As per the American thyroid association, the target TSH values in the first three months is 2.5 mU/L and in the second and third trimester less than 3 mU/L.

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Common Causes Of Hypothyroidism

Dietary deficiency and autoimmune factors are some of the common reasons for hypothyroidism. As thyroid hormones are important during fetal development it is important to check thyroid function tests in pregnancy. When autoimmune factors are responsible for hypothyroidism, thyroid peroxidase antibodies are found to be positive. There are some studies suggesting adverse clinical outcomes in women with high values of thyroid peroxidase antibodies.


Treatment of hypothyroidism revolves around medication with thyroid hormones. Unlike diabetes, lifestyle remedies do not play any role in normalising thyroid functioning. Once treatment is initiated it usually takes about four weeks to get the TSH normalised. Once normalised one may need to continue the same dose till delivery and check the thyroid status again after six weeks to consider if medication has to continue or otherwise.

The health care provider may suggest serial assessment of TSH during pregnancy. Hypothyroid pregnant women once treated and with ongoing medication do not have any adverse outcomes due to hypothyroidism.


To summarise hypothyroidism in pregnancy is quite a common condition and once identified can be treated with thyroid hormone tablets the negative impact of hypothyroidism is overcome within a few weeks of therapy. It is also essential to understand that once treatment is started not stop the treatment abruptly without the concurrence of the health care provider.

(The article is contributed by Dr Gayathri D Kamath, Senior Consultant - Obstetrics & Gynecology, Fortis Hospitals, Bannerghatta Road, Bangalore)

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