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

ABSTRACT

The effects of hypothyroidism induced by oral feeding of thiourea [50 mg/kg] in four indigenous female lambs of 6-8 months of age were studied. Blood samples from jugular vein were collected before and after 40 and 80 days of treatment, and T[4], T[3], LH, FSH, and prolactin in the serum were measured. The weight and dimensions of thyroid gland in hypothyroid lambs were greater than the controls, being associated with a significant decrease in T[4] [P <0.02] and highly significant decrease in T[3] levels [P<0.001]. The levels of LH, FSH, and prolactin in serum did not significantly change during the experiment but the dimensions and weight of the reproductive tract revealed a slight decrease, though not statistically significant. Histological examination of the hypothyroid lambs, showed metaplasia in the secretory cells of the thyroid gland. Follicles in the ovaries were atretic and the endometrial cells were shorter than the controls, indicating that hypothyroidism probably suppresses the ovarian and other reproductive functions of the female lambs