The proportion of pregnant women with abnormal thyroid function in the examination is quite high. Human chorionic gonadotropin (hCG) is secreted by the placenta during the first trimester of pregnancy. Because of its thyroid stimulating hormone-like effect, it can cause temporary and harmless hyperthyroidism in the first three months of pregnancy (increased blood thyroxine concentration).

According to the study, the change occurs in about 2 to 3 out of 1,000 pregnant women, especially those with severe morning sickness. Since this condition is a normal physiological change in pregnancy and tends to disappear by itself during the second trimester, no treatment is required other than necessary follow-up. True hyperthyroidism occurs in about two in a thousand pregnant women, with the most common cause of Graves’ disease accounting for about 90%. This is an autoimmune problem caused by the body's production of antibodies against its own thyroid stimulating hormone receptors (TSHR).

In terms of clinical manifestations, patients’ symptoms vary from feeling uneasy and nervous, to having a rapid heartbeat, sweating and asthma. These symptoms must be distinguished from the discomfort caused by pregnancy itself. As hyperthyroidism can cause a number of maternal complications, such as miscarriage, premature delivery, and even the risk of preeclampsia and congestive heart failure, if you plan to conceive, you should wait until the thyroid function is under control. It is also best to use contraception, as patients with thyroid dysfunction still have a chance to conceive.

If you are pregnant accidentally, you should inform your doctor immediately and receive treatment.

In addition to affecting the mother, hyperthyroidism can also affect the fetus, such as delayed growth in the womb, neonatal hyperthyroidism, and 5% of stillbirths and other complications. Therefore, for patients with hyperthyroidism, in addition to putting thyroid function under control before pregnancy, the thyroid function should be tracked regularly during pregnancy.

Hyperthyroidism in pregnancy is mainly treated with antithyroid drugs, but a few patients may have very serious granular leukocytosis and should discontinue medication immediately, and consider surgical treatment. For other minor side effects, such as skin rashes and allergies, there is no need to stop the medication, but the dosage may need to be adjusted or the medication may need to be changed.

The preferred drug for the treatment of hyperthyroidism in pregnancy is PTU (propylthiouracil) during the first trimester. Although it will cross the placenta, the incidence of abnormal birth, according to statistics, is very low, so pregnant women generally can take it. Methimazole may also be considered during the second to third trimester of pregnancy (3 months after pregnancy).

Throughout the pregnancy, expectant mothers must work with a physician to regularly monitor thyroid function to adjust medication to the lowest effective dose. As for expectant mothers who want to breast-feed after giving birth, there is no reason to be afraid of taking the drug. PTU is found in very low concentrations in breast milk, so breastfeeding normally does not pose a high risk of drug ingestion to the newborn.

Moreover, after childbirth, hyperthyroidism is prone to relapse or re-aggravation, during which we can only rely on regular follow-up of thyroid function and timely adjustment of drug dose, to which every mother-to-be should pay special attention.