Thyroid Storm Caused by Hyperemesis Gravidarum

Transient thyrotoxicosis has been documented in the setting of hyperemesis gravidarum (HG) with elevated human chorionic gonadotropin (hCG) levels. Thyroid storm in pregnancy is rarer and typically associated with autoimmune hyperthyroidism. We described thyroid storm in a primigravid 18-year-old patient due to hCG level elevation secondary to HG, which resolved in the second trimester of pregnancy.

Our patient presented with vomiting, hyperthyroidism, and cardiac and renal dysfunction at 16 weeks' gestation. She was clinically found to have a thyroid storm, with undetectable thyroid-stimulating hormone (TSH) and a free thyroxine level of >6.99 ng/dL. The hCG level was elevated at 246 030 mIU/L (9040-56 451 mIU/L). She was treated with methimazole, saturated solution potassium iodide, and propranolol. Because thyroid autoantibodies were absent, thyroid ultrasound yielded normal results, and thyroid function testing results rapidly improved as the hCG level decreased, the medications were tapered and ultimately discontinued by day 10 of hospitalization. The thyroid function remained normal after discharge.

Because hCG and TSH have identical alfa subunits and similar beta subunits, hCG can bind to the TSH receptor and stimulate thyroxine production. The hCG level peaks at around 8-14 weeks of gestation, correlating with decreased TSH levels in this same time frame. This case emphasizes the relevant physiology and importance of timely and thorough evaluation to determine the appropriate management, prognosis, and follow-up for patients with thyroid storm in the setting of HG.

Although transient thyrotoxicosis is documented in patients with HG, thyroid storm is rare, and our case illustrates a severe example of these comorbidities.