Effects of estrogen administration on parathyroid function in cattle.

Experiment was performed with 6 castrated Holstein bullocks. The animals were divided into two groups of three each, one for experiment and the other for control. The experimental group was given intramuscularly with 120 mg of estrone and 24 mg of estradiol-17 beta daily for 7 days, and the control group with the same dose of solvent without estrogens. The decreasing effect of estrogens on appetite was clearly observed after starting estrogen treatment. The secretory function of the parathyroid gland was improved and the recovery rate of plasma-titratable calcium enhanced in the experimental group after ethylenediaminetetra-acetic acid 2Na infusion as a functional test of the parathyroid gland. Plasma estrogen concentration was kept at the same level as than in healthy dairy cows of the late stage of pregnancy. It was suggested that those changes in calcium metabolism might be mainly due to the acceleration of bone resorption caused by the estrogen injection via the increased secretion of parathyroid hormone.