A. Gonadotropin deficiency (Kallmann syndrome) Kallmann syndrome is a rare genetic disorder with familial and disseminated onset. This X-linked disorder is the result of a single gene variant (Xp22.3 region, named KALIG-1).The main feature of Kallmann syndrome is delayed puberty, and the differential diagnosis also includes delayed puberty. The patient’s testes were extremely atrophic (<50px) and biopsy showed germ cell arrest and mesenchymal cell hypoplasia. Hormonal testing showed low blood lh, fsh and testosterone levels. The patient may be fertile if spermatogenesis is stimulated with fsh and lh. Androgenization of the patient can be obtained by supplemental testosterone or human chorionic gonadotropin (hcg). B. Simple LH deficiency (reproductive anorchidism) This rare condition is due to partial gonadotropin deficiency; LH is sufficient to stimulate testosterone synthesis and spermatogenesis, but testosterone is not sufficient to androgenize the patient. The clinical picture is characterized by anencephaly-like signs, varying degrees of androgenization and feminization of male breasts. The patient had normal testicular volume but low sperm density. Plasma FSH is normal, and LH and testosterone are at low normal values. C. Simple FSH deficiency The disease is extremely rare. The pituitary gland does not secrete enough FSH, but LH is normal, thus the patient has normal androgenization. Testicular volume, blood LH and testosterone levels are normal. Blood FSH are low and do not respond to GnRH stimulation. Clinical manifestations are azoospermia or extreme oligospermia.