Explanation
This patient has secondary hypogonadism presenting with low libido, erectile dysfunction, and a low serum testosterone level. Secondary (ie, pituitary, hypothalamic) hypogonadism can be differentiated from primary hypogonadism by a low or inappropriately normal LH. In addition, whereas in primary hypogonadism the elevated gonadotropin levels stimulate aromatization of testosterone to estradiol, leading to gynecomastia, breast enlargement in secondary hypogonadism is less prominent.
Secondary hypogonadism is a common adverse effect of opioids. Opioids suppress GnRH and LH secretion, leading to reduced Leydig cell testosterone synthesis, decreased spermatogenesis, and testicular atrophy. Additional manifestations can include depression, hot flashes, and osteoporosis. In women, menstrual irregularities are common.
Educational objective: Secondary hypogonadism in men presents with low libido, erectile dysfunction, a low serum testosterone level, and a or inappropriately normal LH. Secondary hypogonadism is a common adverse effect of opioids, which suppress GnRH and LH secretion, leading to reduced Leydig cell testosterone synthesis.
(Choices C and D) Skull fractures and pituitary mass lesions can cause secondary hypogonadism due to disruption of the hypophyseal portal vessels or direct injury to the LH-secreting gonadotroph cells. However, these disorders typically cause a mild to moderate elevation in prolactin (20-200 ng/mL) due to disruption of dopaminergic neurons in the pituitary stalk.
(Choices C and D) Skull fractures and pituitary mass lesions can cause secondary hypogonadism due to disruption of the hypophyseal portal vessels or direct injury to the LH-secreting gonadotroph cells. However, these disorders typically cause a mild to moderate elevation in prolactin (20-200 ng/mL) due to disruption of dopaminergic neurons in the pituitary stalk.
(Choice E) Rapid weight loss (eg, anorexia nervosa) can cause secondary hypogonadism due to suppression of GnRH secretion. Although overweight and obese patients may have mildly low testosterone levels, moderate weight gain in a patient with a normal BMI would not cause symptomatic hypogonadism.
