Familial idiopathic gonadotropin deficiency: a hypothalamic form of hypogonadism.

To date, familial idiopathic gonadotropin deficiency (FIGD) has not been delineated as either a hypothalamic or a pituitary form of hypogonadism. Leydig cell sensitivity to human chorionic gonadotropin (HCG) has also been suggested as subnormal in FIGD. Also, in a few previously reported families the Kallmann syndrome was not clearly ruled out. Data herewith reported on three sibs with FIGD supported the following conclusions: 1) FIGD is due to insufficient hypothalamic luteinizing hormone-releasing hormone (LRH) secretion, 2) the sensitivity of Leydig cells to HCG is normal, 3) LRH treatment may be helpful in these patients, 4) an associated hypothalamic-pituitary-prolactin (PRL) dysfunction may also be present, and 5) FIGD and the Kallmann syndrome are different entities having a similar pathophysiology but different cause and overall clinical picture.