Leydig cell differentiation induced by stimulation with HCG and HMG in two patients affected with hypogonadotropic hypogonadism.

In order to elucidate the ultrastructural characteristics of the precursor cell of Leydig cells and its subsequent differentiation, testicular biopsies from two patients with hypogonadotropic hypogonadism, obtained prior to and after treatment with HCG and HMG, were studied in comparison with those of prepubertal, pubertal and postpubertal testes. Prior to HCG and HMG stimulation, the testicular interstitium of both patients showed the following spindle-cell-types: Fibroblasts, myofibroblasts and a cell-type similar to the myofibroblast but differing from it by the arrangement of microfilaments and the development of the smooth endoplasmic reticulum as well as lipid droplets. It may be considered the precursor of Leydig cells. In the following stages of differentiation observed in the biopsies after treatment, there is a progressive involution of microfilaments and rough endoplasmic reticulum, a transient period of hyperplasia of the Golgi complex, and the definitive development of cell components involved in steroid biosynthesis, such as the smooth endoplasmic reticulum, polymorphic mitochondria with tubular cristae, lipid droplets and diverse lysosomal bodies. From early stages of differentiation, gap junctions occurred between the cells. Numerous axon profiles were also present among the cells. Only in a small percentage of cells did vesicle-bearing axons closely appose the Leydig cell membrane.