[Modulation of the pituitary response to LH-RH by synthetic sex steroids (author's transl)].

This study was planned in order to investigate the response of the pituitary gonadotropin secretion to the luteinizing hormone-releasing hormone (LH-RH) in each menstrual phase (early follicular, late follicular, luteal) of women with regular menstrual cycles, and the effect of synthetic sex steroids on the response of the pituitary to LH-RH, as compared with the response in the late follicular phase. A dose of 200microgram of LH-RH was administered intramuscularly in the early follicular, and luteal phase of regular menstrual cycles. Three groups of 35 normal women administered 3 kinds of sex steroids were also examined on the 8th to 10th day after medication, except for a long-term administration group of norethindrone. The first group was a mestranol group with two subgroups given a daily administration of 20microgram and 40microgram. The second was a norethindrone group, in which one was a short-term group given a daily administration of 5mg, and another was a long-term group given a daily administration of 10mg to 20mg for more than 150 days. The third was a chlormadinone acetate group given a daily administration of 2mg. Blood samples were obtained before the injection of LH-RH at 15, 30, 60, 90, 120, 180 minutes and 24 hours after the injection. Their sera were separated and frozen at -20 degrees C until assayed. Serum LH and FSH concentrations in each experimental group were used as the standard preparation and expressed as mIU/ml of serum. The results were as follows: 1) Serum LH and FSH responsiveness to LH-RH in women with regular menstrual cycles were greater with regard to late folicular, luteal and early follicular phases, respectively, except for a percent increase of serum LH. 2) The serum LH level in response to the LH-RH injection in the early follicular and luteal phases of the cycle showed a biphasic pattern of elevation characterized by the first pool, releasable LH; and the second pool, newly synthesized and stored LH in the pituitary. The biphasic pattern of serum FSH was not confirmed in this experiment. 3) Sham disappearance of biphasic pattern of serum LH release in the late follicular phase was attributed to a shifting of LH form the 2nd pool to the 1st pool due to an increase of the endogenous estrogen. 4) The capacity of the pituitary FSH synthesis and storage showed a slight increase in the late follicular phase, which was supposed to be enhanced by estrogen. 5) The serum LH peak in the mestranol group was observed at 120 minutes after the LH-RH injection, which was significantly elevated in the group given a daily administration of 40microgram, as compared with the control group. The LH concentration occupied in a definite volume tended to be reduced in the first pool after the LH-RH injection in the mestranol group and didnt change in the second pool after the injection, as compared with the control group...