Review Question - QID 108592

This patient is likely presenting with new onset Grave disease. In the first trimester of pregnancy, the treatment of choice is propylthiouracil (PTU), which inhibits central oxidation of iodide to iodine and peripheral conversion of T4 to T3.

Grave disease may first present or worsen in early pregnancy due to the rapid rise in beta-hCG, which cross-reacts with TSH receptors and causes overproduction of thyroid hormones. Hyperthyroidism in pregnancy can be hard to diagnose, as some of the symptoms mimic normal pregnancy. TSH is generally lower in pregnancy due to the increased T4 and T3, but trimester-specific lab cutoffs exist for this reason. In addition to PTU, propranolol can be used temporarily for hyperadrenergic symptoms such as tachycardia, atrial fibrillation, and hypertension. Methimazole, another thionamide drug commonly used to treat hyperthyroidism, is avoided in the first trimester due to increased risk of teratogenicity. Aplasia cutis is classically associated with in utero exposure to methimazole. After the first trimester, PTU is discontinued and substituted with methimazole due to the relatively greater risk of adverse effects with prolonged use of PTU.

Illouz et. al review the diagnosis and management of Grave disease during pregnancy. They discuss pharmacologic management and note that PTU is preferred in the first trimester of pregnancy. They also discuss use of methimazole as well as other adjunctive therapies.

Incorrect Answers:
Answer 1: Intravenous immunoglobulin (IVIG) is an effective treatment of polymyositis but is generally reserved for refractory, progressive symptoms, or patients for whom corticosteroids are contraindicated. It may also be used for myasthenia gravis, a disease caused by autoantibodies toward acetylcholine receptors, resulting in muscle fatigability that most commonly affects the eyes.

Answer 2: Methimazole shares the central mechanism of PTU (oxidation of iodide to iodine). It is generally avoided in the first trimester of pregnancy due to the risk of aplasia cutis, esophageal atresia, and choanal atresia. It is commonly used after the first trimester of pregnancy due to the relatively lower risk of adverse effects with prolonged use when compared to PTU.

Answer 3: Prednisone is used in the management of Grave disease for patients presenting with associated ophthalmopathy. It does not prevent thyroid hormone overproduction. This patient does not present with symptoms of ophthalmopathy and would therefore not be adequately managed with prednisone.

Answer 5: Radioactive thyroid ablation with I-31 is an effective and permanent treatment for Grave disease but is contraindicated in pregnancy due to the risk of fetal hypothyroidism and developmental delay. All women of childbearing age who are planning to receive radioactive iodine should be on reliable contraception and have a negative urine pregnancy test beforehand.

Bullet Summary:
Grave disease in pregnancy should be treated with propylthiouracil in the first trimester and with methimazole in the second and third trimesters.