Hyperthyroidism and Pregnancy (cont.)

Hyperemesis gravidarum is a syndrome of nausea and vomiting that is associated with weight loss of more than 5% during early pregnancy. It is associated with high levels of HCG. Sixty percent of these women have either subclinical (no apparent symptoms) or mildly clinical (mild symptoms) hyperthyroidism, which also usually resolves after the first trimester.

There are other rare conditions associated with abnormal pregnancies that result in hyperthyroidism that are beyond the scope of this discussion.

While the conditions mentioned above are self-limited and associated with changes in the first trimester of pregnancy, women who have hyperthyroidism and become pregnant present another issue.

Pregnancies complicated by uncontrolled hyperthyroidism may result in higher incidences of:

Although any form of uncontrolled hyperthyroidism can complicate pregnancies, the most common form is Graves' disease.

The diagnosis of hyperthyroidism in pregnancy can be complicated since some of the blood tests used for the diagnosis are altered because of the pregnancy. The diagnosis is based on high levels of thyroid hormones, T3 and T4, and a low level of thyroid stimulating hormone (TSH).

The treatment of hyperthyroidism in pregnancy is limited because the safety of the baby must also be considered. Usually, drugs such as propylthiouracil (PTU) and methimazole (MMI) are used. While both of these drugs do cross the placenta and can enter the baby's system, treatment is still preferred because of the poor outcomes associated with not treating these women. PTU is preferred because MMI has been associated with a rare scalp condition in the fetus known as "aplasia cutis."

Medically Reviewed by a Doctor on 12/1/2014

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