Clinicopathological Observations on Thoroughbred Foals with Enlarged Thyroid Gland

Abstract

Seven cases of thoroughbred foals kept on a farm in the Hidaka district of Hokkaido showed bilateral thyroid enlargement from 3 or 4 months after birth. Their serum T₄ levels were remarkably low, whereas T₃ levels were in the normal range. Serum T₄ levels were also low in the other clinically normal foals and their dams kept together. Since the iodine content in pasture soil and grass was very low, iodine deficiency was supposed to be the cause of the disease.