Ability of Luteinizing Hormone (LH) to Acutely Increase Serum Progesterone Levels During the Secretory Phase of the Rhesus Menstrual Cycle

Abstract

The acute response (increase in serum progesterone) of rhesus monkeys to a single intravenous injection of luteinizing hormone (LH), follicle-stimulating hormone (FSH), or prolactin was examined. Blood samples were obtained at 0, 20, 40, 60, and 120 minutes posttreatment with gonadotropins on the morning of Day 6 or 21 of the cycle. Neither FSH nor LH induced an increase in progesterone when administered on Day 6. LH increased serum progesterone at all dose levels (50, 250, and 500 mcg) during the luteal phase of the cycle. Values for LH-treated animals were significantly greater than saline controls (P .05), were positively correlated with dose (.632), and the regression was significant (p .01). The mean effect of 1000 mcg of FSH suggests the ability of exogenous FSH to evoke a slight increase in progesterone secretion. Removal of the LH contaminant in FSH by incubation with LH antiserum did not influence the ability of FSH to increase progesterone levels, however, administration of LH antiserum just prior to giving FSH blocked the previously noted progesterone response to FSH. 60 IU of prolactin was without influence in both phases of the cycle. It is concluded that FSH induces changes in progesterone levels by either affecting the receptor site for LH or causing endogenous release of LH.