Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 25-year-old man is evaluated for a 2-year history of infertility. He and his wife have been unable to conceive since marrying 2 years ago. Analysis of a semen sample provided 3 weeks ago during an infertility evaluation showed azoospermia. The patient has a strong libido and no history of erectile dysfunction. He has no other medical problems and exercises regularly. There is no family history of delayed puberty or endocrine tumors.

On physical examination, the patient appears very muscular. Temperature is normal, blood pressure is 142/85 mm Hg, pulse rate is 55/min, respiration rate is 14/min, and BMI is 22. Visual fields are full to confrontation. There is extensive acne but no gynecomastia or galactorrhea. Testes volume is 4 mL (normal, 18-25 mL) bilaterally. The penis appears normal.

Laboratory studies:

Follicle-stimulating hormone	<0.1 mU/mL (0.1 U/L)
Luteinizing hormone	<0.1 mU/mL (0.1 U/L)
Prolactin	12 ng/mL (12 µg/L)
Testosterone, total	<50 ng/dL (1.7 nmol/L)

An MRI of the pituitary gland shows normal findings.

Which of the following is the most likely diagnosis?

A) Anabolic steroid abuse
B) Nonfunctioning pituitary macroadenoma
C) Primary testicular failure
D) Prolactinoma

MKSAP Answer and Critique

The correct answer is A) Anabolic steroid abuse. This item is available to MKSAP 15 subscribers as item 9 in the Endocrinology and Metabolism section. More information about MKSAP 15 is available online.

This patient is most likely abusing anabolic steroids and possibly other performance-enhancing drugs. Anabolic steroid abuse should be suspected in a muscular man with normal libido, normal erectile function, atrophic testes, infertility, and low gonadotropin and testosterone levels. Fertility can be restored with abstinence from androgens and with gonadotropin injections.

A patient such as this one who has low levels of testosterone and gonadotropins might ordinarily be classified as having secondary hypogonadotropic hypogonadism. However, despite his low testosterone level, there is clinical evidence of adequate circulating androgens, including good muscle mass, normal libido, and erectile function. Therefore, despite the low testosterone and gonadotropin levels, pituitary macroadenoma and prolactinoma are unlikely diagnoses because they cannot explain the patient’s clinical findings. An MRI of the sella turcica to exclude a pituitary tumor is unnecessary.

Common causes of primary testicular failure include Klinefelter syndrome, HIV infection, uncorrected cryptorchidism, previous use of cancer chemotherapeutic agents, irradiation, surgical orchiectomy, and previous infectious orchitis. Although each of these entities is a cause of low testosterone levels, each is also associated with elevated levels of gonadotropins (hypergonadotropic hypogonadism). Primary testicular failure is not a tenable diagnosis in this patient given the findings on clinical evaluation and the suppression of both follicle-stimulating hormone and luteinizing hormone levels.

Key Point

• Anabolic steroid abuse should be suspected in a muscular man with atrophic testes, normal libido, normal erectile function, and a low testosterone level.

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