Levels of Luteinizing Hormone in Sera and Pituitaries of Ewes During the Estrous Cycle and Anestrus

The levels of LH, as determined by radioimmunoassay, in pituitaries and sera of ewes during the estrous cycle and anestrus are described. The mean concentration of LH (μg/g ±SE) in pituitaries was 112 ±15 on day 1 of the estrous cycle and increased steadily to 374 ±47 on day 9. Concentrations in the pituitary fluctuated from 613 ±67 to 537 ±32 on days 11–15 and increased to 998 ±91 during the proestrus. The concentration of LH in serum between the ovulatory peaks was <2 ng/ml during the estrous cycle. The mean concentration of LH in pituitaries in anestrus from May to August varied from 431 ±27 to 300 ±42. The differences among months were not significant. The concentration of LH in serum (ng/ml ±SE) was .25 ±.059 in May, too low to be detected in June and July, and was 1.20 ±0.397 in August. During the estrous cycle the concentration of LH in the pituitary increased from day 1 to proestrus, while the level in serum remained constantly low. The concentration of LH in the pituitary during anestrus does not seem to be directly related to the seasonal breeding of ewes. (Endocrinology86: 568, 1970)