TSH in Serum and Milk of Normal, Thyroidectomized, and Hyperthyroid Lactating Rats

Abstract

TSH was determined by ra-dioimmunoassay in serum and milk of euthyroid, hyperthyroid, and thyroidecto-mized lactating rats. In the normal euthy-roid rats, the average serum TSH concentration was 219 ± 39.8 ng/ml, while the average concentration in milk was 156 ± 9.8 ng/ ml. Five to seven days after thyroidectomy both values were significantly increased to 892 ± 109 and 230 ± 6.5 ng/ml, respectively. In animals treated with a very large dose of T3 for 4 days, serum and milk TSH concentrations were conspicuously decreased to 72 ± 7.1 and 63 ± 6.7 ng/ml, respectively.