Familial normosmic idiopathic hypogonadotropic hypogonadism: is there a phenotypic marker for each genetic mutation? Report of three cases and review of literature.

Normosmic idiopathic hypogonadotropic hypogonadism (nIHH) is familial in one-third of cases and multiple modes of inheritance have been described. Phenotypic spectrum of GNRHR mutations has been found to be widest without any pathognomonic phenotypic feature. However, in subjects of nIHH with TAC3/TAC3R mutations preservation of follicle stimulating hormone secretion is a characteristic feature and has been suggested as phenotypic marker. Despite a paucity of subjects with homozygous frame shift mutations of GNRH, there is remarkable similarity in the phenotypic features and neuroendocrine profile of these few subjects with GNRH mutations. We describe here three members of a family with nIHH and autosomal mode of inheritance with remarkably similar phenotypes.