A 25-year-old man comes to the physician because of right-sided painless scrotal swelling that he noticed yesterday while taking a shower. He is currently sexually active with two female partners and uses condoms inconsistently. He has smoked one pack of cigarettes daily for the last 5 years. He is 170 cm (5 ft 7 in) tall and weighs 70 kg (154 lb); BMI is 24 kg/m2. He appears healthy and well-nourished. His temperature is 37.0°C (98.6°F), pulse is 72/min, and blood pressure is 125/75 mm Hg. On examination, the thyroid is mildly enlarged. Testicular examination reveals an enlarged, nontender right testicle. Laboratory testing shows elevated serum thyroxine and triiodothyronine levels. Scrotal ultrasonography demonstrates a hypoechoic mass within the right testicle. Elevated levels of which of the following substances would most likely explain this patient's symptoms?

Question

A 25-year-old man comes to the physician because of right-sided painless scrotal swelling that he noticed yesterday while taking a shower. He is currently sexually active with two female partners and uses condoms inconsistently. He has smoked one pack of cigarettes daily for the last 5 years. He is 170 cm (5 ft 7 in) tall and weighs 70 kg (154 lb); BMI is 24 kg/m2. He appears healthy and well-nourished. His temperature is 37.0°C (98.6°F), pulse is 72/min, and blood pressure is 125/75 mm Hg. On examination, the thyroid is mildly enlarged.  Testicular examination reveals an enlarged, nontender right testicle.  Laboratory testing shows elevated serum thyroxine and triiodothyronine levels.  Scrotal ultrasonography demonstrates a hypoechoic mass within the right testicle.  Elevated levels of which of the following substances would most likely explain this patient's symptoms?

Quizplus · Accepted Answer

Eductional Objective: Human chorionic gonadotropin (hCG) has a structure similar to TSH.  Patients with testicular germ cell tumors or gestational trophoblastic disease may develop very high serum hCG concentrations, which can stimulate TSH receptors and cause paraneoplastic hyperthyroidism.

A 25-Year-Old Man Comes to the Physician Because of Right-Sided