Recovery of hypothalamic-pituitary-gonadal function with low dose testosterone treatment in a male with congenital hypogonadotropic hypogonadism.

Congenital hypogonadotropic hypogonadism (CHH) is a rare disease caused by deficiency or action of gonadotropin-releasing hormone. While generally considered a long-life condition, CHH can be reversible in about 5%-20% of cases, but mechanisms of reversibility are unknown. We report the case of a male with CHH who began treatment with low dose (20 mg/day) transdermal testosterone to induce pubertal development at age 17. Following the start of treatment, he experienced testicular growth and his serum testosterone concentrations increased beyond the expectations in relation to the dose. Treatment was withdrawn, but this led to the reappearance of symptoms of hypogonadism and a drop in testosterone levels. Testosterone was again prescribed at the same dose and, for the subsequent years, he completed full puberty, including attainment of 20 cc testicular volume, mature secondary sexual characteristics, normal levels of testosterone and only partially arrested germinal function, as demonstrated by inhibin B levels and spermogram. Testosterone treatment was withdrawn three more times, but hypogonadism resumed on each occasion. This case suggests that low-dose testosterone treatment can induce reversal of CHH through the activation, albeit non-permanent, of the hypothalamic-pituitary-gonadal axis, indicating that testosterone administration might be a reliable therapeutic option for reverting GnRH deficiency.