[Hyperthyroidism and an unexpected molar pregnancy]

A molar pregnancy is a rare complication of (non-viable) pregnancy and produces high levels of hCG-hormone. hCG has characteristics similar to TSH, and therefore (severe) hyperthyroidism can occur. The incidence of molar pregnancy is approximately 1 in 1000-1500 pregnancies.

A 23-year-old woman had complaints of discomfort, nausea and vomiting. A urine pregnancy test was negative and laboratory tests showed a severe hyperthyroidism. After referral a molar pregnancy was diagnosed (hCG 1.7 million IU/L). She was treated by curettage. hCG levels insufficiently decreased in the following weeks, and gestational trophoblastic neoplasia was diagnosed. She needed several courses of methotrexate after which she completely recovered.

Severe hyperthyreoidism can be caused by a molar pregnancy. A urine pregnancy test can be negative because of too high hCG-levels, also known as the hook effect. Early recognition and treatment are very important because of the risk of severe complications.