A 47-year-old man comes to the physician complaining of fatigue. He reports low energy and has resorted to energy-boosting drinks to keep him going at work. His sex drive is not "as good as it used to be" when he was in his 30s. He is uncertain whether he gets early-morning spontaneous erections. He also has dull, bilateral, nonthrobbing headaches 3-4 times per month that he describes as a constriction band around his head. The patient denies peripheral vision loss, decreased shaving frequency, or testicular injury. He lives with his girlfriend and has a daughter from a previous relationship.
His other medical problems include hypertension and hyperlipidemia. His current medications are enalapril and atorvastatin. He does not use tobacco, alcohol, or illicit drugs.
His blood pressure is 130/70 mm Hg and pulse is 68/min. His BMI is 25 kg/m². There is no gynecomastia, and body hair distribution is normal for his age. Digital rectal examination reveals normal prostate. Testes have a volume of 20 mL. The remainder of the physical examination is unremarkable.
Complete blood count, serum chemistries, and TSH levels are normal. Serum testosterone measured at 4 PM is 256 ng/dL (normal, 300-800 ng/dL) .
Which of the following is the most appropriate next step in evaluating his low testosterone level?

Question

Quizplus · Accepted Answer

11ec193a_97bf_8032_853d_4b0f0d028361_MD0002_00 This patient's fatigue and decreased libido could be from testosterone deficiency or another etiology. Serum testosterone measurement is the most important test to diagnose male hypogonadism. Testosterone values follow a circadian rhythm and are highest early in the morning around 8 AM and lowest around 8 PM. Serum testosterone levels also decrease with age. Total testosterone level < 300 ng/dL in a blood sample between 7 AM and 10 AM in patients with reported clinical features is suggestive of testosterone deficiency. This patient's serum testosterone level is low, but the blood sample was drawn at 4 PM. The testosterone level may be on the lower end in normal patients at this time. The appropriate next step is to measure serum testosterone level in the early morning. The patient would likely require testosterone therapy (eg, transdermal or intramuscular) if the morning level is also low (Choice E). (Choice A) Total serum testosterone levels are usually accurate in assessing testosterone secretion. However, serum free testosterone level is recommended when sex hormone-binding protein abnormality is suspected, such as in obesity or male senescence. This patient is neither obese nor of advanced age. (Choice B) Once the diagnosis of testosterone deficiency is established, serum FSH and LH levels are helpful to differentiate between primary and secondary hypogonadism. Low testosterone with elevated LH and FSH is consistent with primary hypogonadism. Low testosterone with normal or low LH and FSH is consistent with secondary hypogonadism. (Choice C) MRI is indicated if there is a suspicion of secondary hypogonadism. This patient has no symptoms suggestive of pituitary dysfunction, and his headache appears to be tension type. Educational objective: Total testosterone levels < 300 ng/dL in a blood sample taken between 7 AM and 10 AM in patients with reported clinical features are suggestive of testosterone deficiency. Measurement of free testosterone level is not usually required unless the patient is obese or elderly. Treatment includes transdermal or intramuscular testosterone preparations. __________ References: Testosterone therapy in men with androgen deficiency syndromes: An Endocrine Society clinical practice guideline. (http://www.ncbi.nlm.nih.gov/pubmed/20525905)

A 47-Year-Old Man Comes to the Physician Complaining of Fatigue