Serum LH,FSH and Prolactin Levels During the Estrous Cycle in the Hamster

Summary

Serum LH, FSH and prolactin was measured by radioimmunoassays in 21 mature female golden hamsters at 9 am on each morning of the 4-day estrous cycle and also at 6 pm on the day of proestrus. All 3 hormones showed peak values at 6 pm on proestrous day, and by the following morning (estrus) LH and prolactin had returned to basal levels. Serum FSH remained as high on the morning of estrus as on the afternoon of proestrus, and although it fell on the morning of metestrus it was still higher than on the mornings of diestrus and proestrus. The persistence of high FSH release on the mornings of estrus and metestrus may be related to the luteotropic function ascribed to FSH in the hamster. The peak rise in all 3 hormones on the afternoon of proestrus in the hamster is similar to that observed for these 3 hormones in the serum of cycling female rats.