A 40-year-old man presents to the clinic with a 6-month history of fatigue, decreased libido, and erectile dysfunction. He has a past medical history of hypertension and is currently taking amlodipine. He reports drinking one glass of wine per week and does not smoke cigarettes or use illicit drugs. He exercises regularly. Vital signs are within normal limits. Physical examination reveals bilateral gynecomastia. There are no visual field defects or other neurological abnormalities. Laboratory results are as follows:
Repeat early-morning testosterone level is 155 ng/dL. Which of the following is the most appropriate next step in the management of this patient?
B) Measure serum prolactin level
This patient presents with symptoms of secondary (central) hypogonadism, as indicated by his low testosterone levels and inappropriately normal gonadotropin (FSH and LH) levels. Secondary hypogonadism can be caused by various factors, including mass lesions in the hypothalamus or pituitary, hyperprolactinemia, long-term use of glucocorticoids or opiates, and severe systemic illness.
The most appropriate next step from the provided answer choices is to measure serum prolactin level, as elevated prolactin can inhibit gonadotropin-releasing hormone (GnRH) secretion, leading to low levels of FSH and LH and, subsequently, low testosterone. Additionally, patients with elevated prolactin due to prolactinoma may have headaches and visual field defects due to compression of the optic chiasm by a pituitary adenoma.
Answer choice A: Discontinue amlodipine, is incorrect. Discontinuing amlodipine is unlikely to resolve the patient's symptoms as antihypertensive medications generally do not cause significant hypogonadism.
Answer choice C: Measure transferrin saturation, is incorrect. Measuring transferrin saturation could help diagnose hemochromatosis, but this condition typically presents with other symptoms such as skin pigmentation and diabetes, which this patient does not have. Clinically significant iron overload causes increased serum ferritin and transferrin saturation.
Answer choice D: Prescribe sildenafil, is incorrect. Sildenafil can help with erectile dysfunction but does not address the underlying cause of this patient’s hypogonadism.
Answer choice E: Ultrasonography of the testes, is incorrect. An ultrasound of the testes may be useful in evaluating primary testicular failure but is not indicated here since the patient's findings suggest a central cause for hypogonadism.
Key Learning Point
In a patient with symptoms of secondary hypogonadism, such as low testosterone and normal gonadotropin levels, the best next step is to measure serum prolactin levels to evaluate for hyperprolactinemia, a common cause of central hypogonadism.
