Some Factors Affecting Gonadotropin Levels in Sheep. ∗

Summary

LH and FSH activities have been determined in blood and pituitaries obtained from intact and gonadectomized male and female sheep. Serum LH activity is not altered in this species by either castration or ovariectomy. FSH activity in the blood increases following either operation. The increase in potency of the ewe pituitary following ovariectomy is due almost entirely to an increase in FSH concentration. In the male both LH and FSH levels increase. Changes in serum LH activity occur in the intact ewe which appear to be related to the time of year and particularly to the onset of cyclic activity.