A pt reported absence of nocturnal or full-bladder erections

[shrikant]

A 68-year-old man was referred to our institution for evaluation of impotence, which had been present since he was 45 years of age. He reported absence of nocturnal or full-bladder erections. Biochemical evaluation when he was 59 years old revealed a high prolactin level. The patient was treated with bromocriptine, but treatment was discontinued because of gastrointestinal side effects. Several years later, the patient was found to have hypothyroidism associated with recurrent episodes of “hypoglycemia” characterized by palpitations, tachycardia, sweating, documented hypoglycemia, and rapid response to administration of glucose, for which thyroid hormone replacement therapy was initiated and consumption of frequent small meals was recommended. His past medical history included cholecystectomy but otherwise was unremarkable; he had no history of diabetes mellitus, orchitis, or trauma. His family history was remarkable for a brother with hypothyroidism and a sister with colon cancer. Review of systems disclosed a 39.5-kg weight loss during a 4-year period, gradual loss of axillary and pubic hair, fatigue, and muscle weakness. He denied having headaches or visual problems. The patient was taking no other medications.
Which one of the following is the least likely cause of this patient’s impotence?

Psychogenic impotence

Hypothyroidism

Hyperthyroidism

Hypogonadism

Hyperprolactinemia

[shrikant]

Psychogenic impotence

Psychogenic causes account for approximately 25% of all cases of impotence. Such cases are usually sudden in onset and preceded by a specific event. Other features include normal morning erections and absence of chronic health problems or medications. Psychogenic impotence is a diagnosis of exclusion and least likely in our patient because the history suggests an organic cause for the impotence. Both hypothyroidism and hyperthyroidism have been implicated as causes of impotence. Prepubertal hypothyroidism can affect male gonadal function and impair secretion of gonadotropin. If untreated, the condition may lead to testicular atrophy. In severe hypothyroidism, the resultant hyperprolactinemia may contribute to reduced secretion of testosterone and lead to impotence. Impotence, however, is an uncommon initial complaint in patients with hypothyroidism. Hyperthyroidism-associated impotence probably results from changes in sex steroid-binding globulin or is evidence of excess estrogen biologic activity; however, the exact mechanism is unclear. This cause is unlikely in our patient because he had symptoms before thyroid hormone replacement therapy. Hypogonadism can be primary or secondary to a hypothalamic or pituitary process. Measurement of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels will help distinguish these two conditions. Substantially increased LH and a low testosterone level suggest primary testicular disease, whereas a low or normal LH level and a low testosterone level suggest hypothalamic or pituitary dysfunction.1 Hyperprolactinemia from any cause can lead to hypogonadotropic hypogonadism by inhibiting secretion of gonadotropin.