Question of the Week

For April 28, 2015

A 47-year-old obese man who is divorced reports fatigue and diminished libido. Starting a year ago, but not before then, his interest in sex waned; he now rarely awakes with an erection, and he achieves only a modest erection when masturbating. He has occasional morning headaches. He denies any loss of axillary or pubic hair or any history of testicular trauma or infection with mumps. His experience of puberty was normal. He has two healthy children, ages 15 and 17 years.

His BMI is 38. Axillary hair and pubic hair are normal. Each testicle is about 10 cc (reference range, 15–25). Visual fields are intact to confrontation.

Laboratory testing yields the following results:

Patient value

Reference range

Luteinizing hormone (mIU/mL)

1.8

2.0–12.0

Prolactin (ng/mL)

5.2

0–15.0

Total testosterone (ng/dL)

210

270–1070

Sex hormone–binding globulin (nmol/liter)

30

13–71

Thyroid-stimulating hormone (μU/mL)

1.52

0.5–4.7

Free thyroxine (ng/dL)

1.5

0.8–1.8

What is the most appropriate next step in evaluating this patient?

MRI of the pituitary
Karyotype testing
Testicular ultrasound
Urine screen for opioids
Sleep study