Pregnancy presenting as hyperthyroidism with negative urine pregnancy test.

A 22-year-old lactating mother presented with symptoms of uneasiness, palpitation, tachycardia and exophthalmos. She had an abdominal lump suggestive of 26 weeks uterine size but her urine pregnancy test was negative. Her thyroid profile was suggestive of hyperthyroidism. Gynaecological and ultrasonographic findings revealed a hydatidiform mole. She had a low β-human chorionic gonadotropin level that surprisingly increased after suction and evacuation. The paradoxical findings that appeared as erroneous laboratory results could be explained by the 'high-dose hook effect' after a review of literature. One week after the evacuation, the patient's thyroid profile and symptoms resolved completely without any treatment for hyperthyroidism.