A Possible Role for Reproductive Hormones in Newborn Boys: Progressive Hypogonadism without the Postnatal Testosterone Peak

Healthy boys have a considerable production of reproductive hormones during the first postnatal months, the biological significance of which is poorly understood. We report on cases of male infants with hypogonadism (hypogonadotropic hypogonadism, n = 1; panhypopituitarism, n = 2) who showed lack of penile growth and involution of the scrotum. In two boys, diagnoses were obtained in early infancy and hormonal measurements at 3-4 months of age showed serum testosterone levels below detection limits in both low inhibin B (37 and 199 pg/mL, respectively; normal range, 193-563 pg/mL) and low to undetectable gonadotropins LH, undetectable and 0.07 IU/L (normal range, 0.65-2.69 IU/L), respectively; FSH, 0.18 IU/L in both (range, 0.86-2.52 IU/L). In a third boy, gonadotropin deficiency was diagnosed at 3 yr of age by undetectable serum levels of FSH and LH both before and after stimulation with GnRH. All cases required hormonal treatment with testosterone, administered as suppositories in daily doses between 1 and 5 mg, which reintroduced male genital development. Our observations suggest that normal phallic and scrotal development in humans is dependent on intact testosterone secretion during early infancy. Additionally, the diagnosis of gonadotropin deficiency may be established in a short-time window postnatally by measurement of spontaneous serum concentrations of reproductive hormones.