Hyperemesis gravidarum and hyperthyroidism: distinguishing transient and persisting hyperthyroidism in pregnancy

Objective: We review whether hyperemesis gravidarum can be the only symptom of hyperthyroidism in pregnancy and how transient hyperthyroidism during p regnancy can be distinguished from persistent hyperthyroidism. Methods: We review three patients with thyrotoxicosis in early pregnancy wh o presented with hyperemesis. Results: All patients had persistent vomiting. ketonuria and weight loss an d did not respond to intravenous hydration and antiemetics. Further testing showed hyperthyroidism. One patient had autoantibody-negative immunothyrop athy, one had Craves disease (diffuse toxic goiter), and one had toxic nodu lar goiter. Hyperemesis resolved with thyreostatic treatment. Conclusion: Hyperemesis can be the only symptom of thyrotoxicosis during pr egnancy, which can mask the typical clinical features of hyperthyroidism. T hyroid function tests cannot always distinguish Graves disease from transie nt hyperthyroidism during pregnancy. A lack of thyroid autoantibodies and a self-limiting course by the 18th week of gestation support the diagnosis o f gestational hyperthyroidism. In contrast, persisting forms of hyperthyroi dism require thyreostatic treatment.