The critical endocrine features of pulsatile GnRH administration are most evident when this drug is administered to patients with profound forms of hypogonadotropic hypogonadism (e.g., Kallmann syndrome) that are characterized by a virtually complete absence of endogenous GnRH secretion and primary amenorrhea. This evidence concerns the gene GNRH1 and hypogonadotropic hypogonadism.