Effect of experimental zinc deficiency on thyroid gland in guinea-pigs.

Zinc deficiency was produced experimentally in guinea-pigs fed on a diet containing 1.03 mg Zn/kg over a period of 45 days. Clinical signs exhibited in Zn-deficient (ZnD) animals were depression with abnormal posture, scaly skin lesions on various parts of the body, oedematous swelling on hind limbs and marked alopecia. There was no effect on food intake. Serum studies in ZnD group revealed significant decreases in the concentrations of Zn from 20 days onwards, and tri-iodo-thyronine (T3) and thyroxine (T4) from 30 days onwards. Thyroid glands of ZnD animals were smaller in size and pale or whitish pale in colour. Histopathologically, these glands showed changes of atrophy and degeneration in the follicles. It could be concluded that the depletion in serum T3 and T4 due to Zn deficiency was related to thyroid lesions.