Primary hypogonadism and 13/15 chromosome translocation in Prader-Labhart-Willi syndrome.

A 14-year-old male with Prader-Labhart-Willi syndrome (PLW) had hypogonadism, normal serum gonadotropin levels and 13/15 chromosome translocation. The 24-hour pattern of LH and FSH secretion was normal and comparable to that observed in males at the middle to late stage of puberty. LH rose during sleep and LRH infusion. Basal serum testosterone was low, in the 60-136 ng/dl range, and rose modestly during sleep, LRH and HCG. The 24-hour mean concentrations of androsterone, androsterone sulfate, dehydroepiandrosterone, dehydroepiandrosterone sulfate and prolactin were comparable with normal adolescent males. Biopsy of an undescended testis revealed poor morphology with disorganized spermatogenesis and normal Leydig and Sertoli cells. The 13/15 chromosome aberration was a balanced Robertsonian translocation occurring in his mother and in 5 of 6 siblings, although only the patient had PLW. These data indicate that hypogonadism in PLW is not necessarily hypothalamic-pituitary in origin and that D-chromosome translocations, or deletions per se are not sufficient to explain the etiology of PLW.