[A morphological study of the testis in patients with idiopathic male infertility--quantification and ultrastructure of Leydig cells].

Testicular biopsy was performed on 51 patients with idiopathic male infertility and 13 normal fertile adults. The biopsied specimens were examined by light and electron microscopy. A quantitative evaluation of Leydig cell number was made by determining the mean number of Leydig cells per one cross section of seminiferous tubule in the entire histologic section of each specimen, which was defined as "Leydig cell index". In both oligospermic and azoospermic groups, the Leydig cell index was significantly elevated as compared with in that the normal group, which indicated the presence of Leydig cell hyperplasia in the infertile testis. In addition, this index significantly correlated with serum luteinizing hormone and follicle stimulating hormone levels but not with serum testosterone level. Leydig cells were classified into three types based upon their morphological characteristics. Type I Leydig cells were functionally active and mature ones, with a smooth-surfaced round or oval nucleus, had abundant smooth endoplasmic reticulum (SER), characteristic mitochondria and relatively few lysosomes. Type II Leydig cells were functionally less active, and contained an irregularly shaped nucleus, less abundant SER, mitochondria with undeveloped cristae and relatively few lysosomes. Type III Leydig cells included immature and regressive cells, which were considered to have almost no hormone secreting function. The immature Leydig cells were spindle-shaped and had few cell organelles. The regressive cells had poorly developed SER and many secondary lysosomes in the cytoplasm. In the normal group, type I Leydig cells are the most numerous but in the infertile groups type II Leydig cells are the most numerous. However, in the latter, there is no significant difference in relative number of each Leydig cell type among the groups classified according to the number of sperm or Leydig cell. In summary, Leydig cell hyperplasia observed in the testis of the infertile patients was supposed to be induced by the elevation of the serum LH. Despite of the significant increase in Leydig cell number, the serum testosterone was not elevated, and this was considered to be due to the fact that the hyperplastic cells are mainly composed of functionally less active type II Leydig cells. In addition, especially in the severe hyperplastic group, not only type II but also type I Leydig cells increased in number. However, in this group, the serum testosterone level was not elevated. Therefore, the function of type I Leydig cells was suggested to be impaired.