A window of opportunity: the diagnosis of gonadotropin deficiency in the male infant.

A common cause of micropenis is congenital hypogonadotropic hypogonadism, whether isolated or associated with multiple pituitary hormone deficiencies. The postnatal surge in FSH, LH, and testosterone in the male infant as a consequence of the continued function of the fetal GnRH pulse generator provides a 6-month window of opportunity to establish the diagnosis of hypogonadotropic hypogonadism and alert the clinician to the possibility of its association with multiple pituitary hormone deficiencies. When ACTH or GH deficiency or both deficiencies are present, hypoglycemia and cortisol deficiency can lead to neonatal and infantile death or increased morbidity. Establishing the diagnosis of hypogonadotropic hypogonadism in infancy preempts the uncertainties and delays in distinguishing constitutional delay in puberty from hypogonadotropic hypogonadism. Accordingly, hormone replacement therapy can be initiated at the normal age of pubertal onset. The ontogenesis of infantile testicular function, including the possible significance of the infantile surge in gonadotropins and testosterone, is reviewed. The molecular basis for certain developmental disorders associated with hypogonadotropic hypogonadism and micropenis is considered and the management and treatment of congenital hypopituitarism discussed.