[Effects of hypothyroidism on the reproductive system of male lambs]

ABSTRACT

The effects of hypothyroidism induced by oral feeding of thiourea [50 mg/kg] in four indigenous male lambs of 5-7 months of age were studied. Blood samples from jugular vein were collected before and after 40 and 80 days of treatment and the levels of T[4], T[3], LH, FSH, prolactin and testosterone in the serum were estimated, and compared with two negative controls. The weight and dimensions of thyroid gland in hypothyroid lambs were greater than the controls being statistically significant for the length of the gland [P <0.05] and highly significant decrease for the levels of T[4] and T[3] in the serum [P <0.001]. The levels of LH, FSH and prolactin in the serum did not significantly change during the experiment while the dimensions and weight of the testis showed a decrease though not statistically significant. However, testosterone [T] was not detectable in the serum, and the dimensions of accessory glands did not change. Histological examination of the hypothyroid lambs showed hyperplasia and metaplasia in the secretory cells of the thyroid gland, with a complete degeneration of germ cells in seminiferous tubules of the testis. There was an increase in the number of leydig cells and their surrounding fibroblasts, but these cells also showed signs of degeneration. No sperm cells were observed in the epididymis. Degeneration and vacuolation were observed only in the seminal vesicle cells. It is concluded that hypothyroidism diminishes all the germ cells and hormone producing cells in the testis