Hypogonadism and Leydig cell hypoplasia unresponsive to human luteinizing hormone (hLH)

A 22-year-old man with hypogonadism, Leydig cell hypoplasia, high plasma LH, and normal plasma FSH was given human chorionic gonadotropin (hCG) and human luteinizing hormone (hLH) in order to assess testicular testosterone responses to exogenously administered gonadotropins. The maximal testosterone level detected after six doses of hCG, 5000 IU per dose given intramuscularly (IM) was 256 ng/dl. After eight doses of hLH, 550-1100 IU per dose given IM, the plasma testosterone level was unchanged, 100-200 ng/dl. The lack of a response to exogenously administered gonadotropins in our patient suggests that there is a primary testicular lesion causing the hypogonadism. Our patient's own LH is probably biologically active since there was no response to human LH, a pituitary extract with a known biopotency (LER 1549). Our patient's endocrine abnormality is apparently another facet in the spectrum of findings described in patients with Leydig cell hypoplasia or aplasia. Other features of this entity can include female pseudohermaphroditism, ambiguous genitalia, hypogonadism, delayed puberty, and the presence of biologically inactive LH.