Thyroid physiological changes during pregnancy

The thyroid gland is a small butterfly-shaped endocrine gland located in the front of the neck. Although very small with a size of about 50 x 20 x 20mm, they have a very important job for the body to secrete thyroid hormone to help the body metabolize and use energy.

To meet the increased metabolic demands during pregnancy, the function of the thyroid gland undergoes physiological and functional changes. This is reflected through laboratory parameters such as: total T3, elevated total T4, while FT4, FT3 are normal. Accordingly, the T3, T4 index will increase about 50% in the first half of pregnancy and will return to normal in the last weeks of pregnancy.
Interestingly, beta hcG - a hormone secreted by the placenta during pregnancy is structurally similar to TSH - a hormone secreted by the pituitary gland to stimulate the thyroid gland to produce thyroid hormone.
The chart below depicts the changes in the levels of two hormones, hCG and TSH, of the mother's body during pregnancy.

During pregnancy, the amount of HCG in the mother's blood increases gradually right after fertilization and peaks at 11-12 weeks of gestation. It is during this phase that thyroid-stimulating hcG increases total T3, T4 levels while FT3, FT4 increase slightly but still within normal limits and TSH will be suppressed respectively. In the next stage of pregnancy, when hcG levels gradually decrease, T3, T4 levels will also decrease and return to normal limits.
Therefore, thyroid disease and pregnancy are closely related. Specifically, at each stage of pregnancy there is a change in the normal threshold for thyroid function tests. To know if you really have thyroid disease or just a physiological change of the thyroid gland during pregnancy, pregnant women need to be examined by a specialist doctor. Pregnant women with thyroid disease that really need treatment will be closely monitored and promptly treated to have a safe and healthy pregnancy.

Just like men or women who are not pregnant, pregnant women can experience thyroid problems such as goiter, hyperthyroidism, hypothyroidism, thyroid nodules, thyroid cancer... manifestations and different treatment methods.
3.1. Hyperthyroidism This is a condition in which the thyroid gland produces too much thyroid hormone. Depending on the severity, it can affect mother and baby in different degrees such as miscarriage, premature birth, hypertension, preeclampsia, heart failure ...
3.1. Hypothyroidism This is a condition in which the thyroid gland does not produce enough thyroid hormone to meet the needs of pregnancy, leaving serious consequences, especially in the first 3 months of pregnancy. Because in the first 3 months of pregnancy, the fetus has not yet synthesized thyroid hormone and is completely dependent on the mother.
3.3. Thyroid nodules, thyroid cancer Thyroid ultrasound is the most effective method of diagnosing thyroid nodules. Thanks to the ultrasound method, it will help detect thyroid nodules, suspect high or low-grade cancer. In the case of pregnant women with high suspicion of cancer, the doctor may prescribe a fine needle aspiration method to ensure safety for pregnant women. Depending on each specific case, the doctor will give the most reasonable advice to monitor and treat thyroid nodules for the patient. In cancer diseases, thyroid disease, if detected and treated early, will bring a good prognosis and the ability to cure the disease is very high. Therefore, the examination, screening and early detection of thyroid disorders are very important. In the case of pregnant women with thyroid disease requiring treatment, they will be closely monitored and treated promptly to have a safe pregnancy.
Understand the common medical problems of pregnant women, as well as the risks and potential risks that threaten the health of mother and baby. Currently, Vinmec International General Hospital has implemented a promotion program to screen for thyroid cancer and pathology, helping patients to detect their medical condition early and have an effective treatment regimen. The examination, screening and early detection of diseases not only ensure the health of both mother and baby, but also save maximum treatment costs, improve quality of life and life expectancy.