146 Obstetrics and Gynecology Board Review •••
❍ Which thyroid hormone is the least likely to cross the placenta?
Thyroid-stimulating hormone (TSH).
❍ What is the most common etiology of hyperthyroidism in pregnancy?
Graves disease.
❍ Name general signs and symptoms of hyperthyroidism.
Tremors, nervousness, tachycardia, frequent stools, sweating, heat intolerance, weight loss, goiter, insomnia,
palpitations, and hypertension.
❍ What are symptoms and signs specific to Graves disease?
Ophthalmopathy (including lid lag and lid retraction) and dermopathy (including localized or pretibial
myxedema).
❍ What complications may result from inadequately treated thyrotoxicosis?
Preterm delivery, severe preeclampsia, heart failure, low birth weight infant, and fetal loss.
❍ What effect may maternal Graves disease have in the neonate?
The neonate may have either immune-mediated hypothyroidism or hyperthyroidism due to inhibitory
immunoglobulin (TBII) or thyroid-stimulating immunoglobulins, (TSI) respectively, which cross the placenta.
❍ What medications can be used to manage hyperthyroidism and what are their mechanisms of action?
Methimazole and propylthiouracil (PTU) both inhibit thyroperoxidase, which is necessary for addition of iodine
to tyrosine to form T3 and T4.
❍ What is the side effect of major concern for women taking the thioamines PTU or methimazole?
Agranulocytosis, which occurs in 0.1% to 0.4% of patients taking thioamines, usually presents with fever and sore
throat. Thrombocytopenia, hepatitis, vasculitis, rash, fever, nausea, and loss of sense of smell or taste are other
possible side effects.
❍ What is the recommended treatment of hyperthyroidism in pregnancy and why?
PTU should be used in the first trimester because methimazole has been associated with choanal and esophageal
atresia. After the first trimester PTU should be converted to an equivalent dose of methimazole because PTU can
cause hepatotoxicity.
❍ What is the treatment of hyperthyroidism in contraindicated in pregnancy?
Iodine 131 because it may also cause fetal thyroid gland destruction. Women should avoid pregnancy for 6 months
after receiving radioactive iodine ablation.
❍ What is the clinical presentation of thyroid storm?
Fever; tachycardia out of proportion to fever; altered mental status—restlessness, nervousness, confusion, seizures;
vomiting; diarrhea; cardiac arrhythmia. Thyroid storm complicated 1% of pregnancies with hyperthyroidism.