Human hypospermatogenesis. Histopathology and ultrastructure.

Testicular biopsy specimens from 25 patients with hypospermatogenesis were studied with both light and electron microscopy. In five cases, the condition was found in only one testis. In hypospermatogenesis, the number of the spermatogenic cells was reduced by about half, although there was considerable variation in different cases. The numbers of all types of germ cells (spermatogonia, spermatocytes, and spermatids) were reduced, but few degenerative cells were seen. This indicates that the primary defect in hypospermatogenesis is in the stem cell population, which is somehow inhibited from entering the line of germ cell differentiation, but that once the cells are committed to this line of differentiation spermatogenesis proceeds normally.