Issue #113
May 2021
Thyroid conditions during pregnancy

Thyroid conditions are relatively common during pregnancy and may occur in women with known thyroid disorders, or for the first time during pregnancy. Chemical Pathologist, Dr Tina Yen explains that as many of the symptoms of new thyroid disease can mimic the hormonal changes a woman experiences during a normal pregnancy, such as tiredness, feeling hot or feeling bloated, these disorders can be difficult to diagnose and require laboratory tests.

“Undetected and untreated thyroid conditions during pregnancy can have serious consequences, including premature birth, preeclampsia (a severe increase in blood pressure) miscarriage and stillbirth, amongst other problems. However, if a thyroid condition is diagnosed and treated during pregnancy then it is still possible to have a healthy pregnancy and a healthy baby.

“During pregnancy, a women’s thyroid will adjust to provide thyroid hormones that are critical for foetal brain development. Pregnancy specific reference ranges are therefore required for first, second and third trimester to accurately diagnose a thyroid conditions disorder in pregnancy. Some Australasian laboratories already report trimester specific reference ranges,” said Dr Yen.

The two most common types of thyroid conditions are hyperthyroidism, where the thyroid is overactive, and hypothyroidism where the thyroid is underactive. Hyperthyroidism is most commonly caused by Graves’ disease (an autoimmune disorder), and excessive exposure to iodine (e.g. supplements, dietary sources). The third cause of hyperthyroidism is hyperemesis gravidarum which is a condition of severe nausea and vomiting in early pregnancy caused by excessively high HCG levels and thyroid stimulation.

Symptoms of hyperthyroidism include weight loss (or lack of expected pregnancy weight gain), heat intolerance and faster heart rate. Symptoms of hypothyroidism include cold sensitivity, extreme tiredness, constipation and dry skin, or may be subclinical with few or no symptoms but abnormal levels of thyroid hormones.[1]

“Women who have a pre-existing thyroid condition should speak to their doctor to keep these conditions in control during pregnancy, especially for the first trimester. Screening for thyroid conditions in pregnancy is currently not recommended for everyone, however, it is recommended in those women who are considered to be higher risk. This includes those women who are being treated for a thyroid condition; have previously had a thyroid condition; have an autoimmune disorder; have type 1 diabetes; or have had high-dose neck radiation or treatment for hyperthyroidism.

“Women with known thyroid disease will need to have their treatment adjusted and more frequently monitored during pregnancy,” said Dr Yen.

As symptoms of both hyperthyroidism and hypothyroidism are similar to a normal pregnancy, thyroid tests can be more difficult to interpret. Those who are experiencing symptoms of a thyroid condition should speak with their doctor. If a thyroid disorder is determined, then close pathology monitoring and treatment is essential.







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