Hypogonadotropic hypogonadism; the genetic defect. A hypothesis based on human and animal prototypes.

X-linked hypogonadotropic hypogonadism (HH) in humans may involve the genes responsible for the development and migration of GnRH neurons from the olfactory placode to the hypothalamus. The evidence for this includes the lack of hyperprolactinaemia in cases of X-linked HH, the associated abnormalities in the context of contiguous gene syndromes involving Xp deletions, and pertinent anatomical findings. The genetic defect in human HH appears, therefore, to be different from that found in the hpg mouse model.