Effect of vitamin D deficiency on testicular function in the rat

To study the effect of vitamin D deficiency on testicular function, 30-day-old male rats were put on a vitamin-D-deficient diet. At 120 days of age, the testicular function of these animals was compared with that of rats of the same age group fed, ad libitum, a diet containing vitamin D and rats fed on a restricted amount of diet with vitamin D. In vitamin-D-deficient rats, there was a significant reduction in the total body weight, testicular and epididymal sperm count and testicular glutamyl transpeptidase activity (an index of Sertoli cell function) as compared to control group rats, but there was no difference in the testicular lactate dehydrogenase activity (an index of germ cell function). Histological examination of the testis in vitamin-D-deficient rats revealed a significant reduction in the Leydig cell count along with degenerative changes in the germinal epithelium. Histological examination of the tibia revealed excess of osteoid in vitamin-D-deficient rats only. On the other hand, in undernourished rats given a normal amount of vitamin D, the only significant change was a reduction in total body weight. These results suggest that vitamin D deficiency retards spermatogenesis by interfering with the function of Sertoli and Leydig cells.