Pathological and biochemical studies on experimental hypothyroidism in growing lambs

Secondary iodine deficiency was experimentally produced in growing male lam bs by oral administration of 50 mg/kg bodyweight of Thiourea daily for 3.5 months. At the end of the experiment the animals became weak, emaciated, an aemic, significantly reduced in body weight with facial oedema and alopecia at thigh, legs and abdomen. The clinical analysis showed significant reduc tion in erythrocyte and leucocyte numbers and in levels of triiodothyronine and testosterone at the end of the experiment. The histopathological pictu re of the thyroid gland revealed hyperplasia of the follicle-lining epithel ial cells which project into the lumen. The lumens of the follicles are dev oid of colloid. The testes showed ill-developed small, empty seminiferous t ubules. In the liver, the hepatocytes showed degeneration and vacuolation w ith proliferation of Kupffer cells, which contain haemosiderin pigment. The kidney showed glomerular lipidosis with accumulation of haemosiderin pigme nt in the cytoplasm of the renal tubules. Hyperkeratosis of the epidermis a ssociated with excessive keratin formation within the hair follicles was de tected. In conclusion, deficiency of iodine causes hypothyroidism which lea ds to retardation of growth, reduced wool production and interferes with se xual maturity of growing male lambs.