Summary. The interactions of oestriol and progesterone were studied in a series of assays for oestrogenic and progestational activities, and the responses were compared with data on progesterone-oestrone combina¬ tions in the same tests. The vaginal effects of these two oestrogens do not seem to differ, whereas the interactions of oestriol and progesterone are quite different from the interactions of oestrone and progesterone when uterine end-points are considered. Since oestriol is the dominant aromatic steroid excreted during pregnancy and the luteal phase of the menstrual cycle, we feel that explanations for many unsolved problems of luteal-phase and pregnancy physiology may reside in these interactions.

We investigated the effects of single doses of mesulergine on basal and thyrotropin-releasing hormone (TRH)-stimulated serum levels of several anterior pituitary hormones in healthy men and defined its kinetics. We also compared the effects on serum prolactin (PRL) levels of three doses (0.1, 0.35, and 0.5 mg) of mesulergine to those in response to 2.5 mg bromocriptine. Secretory rates of PRL before the first dose of TRH were not affected by any dose of mesulergine or bromocriptine. TRH-stimulated PRL secretion was not altered by 0.1 mg mesulergine but was blunted by both the 0.35- and 0.5-mg doses at 10 A.M. and 1 P.M. Bromocriptine inhibited TRH-stimulated PRL secretion at 10 A.M. and 8 P.M. When analyzed as the 8 A.M. to 8 P.M. and the 8 P.M. to 9 A.M. (day 2) intervals, PRL secretion was not changed by 0.1 or 0.35 mg mesulergine but was suppressed during both periods by the 0.5-mg dose. A dose-response relationship was evident, however, between mesulergine and PRL secretion during both the 8 A.M. to 8 P.M. (R2 = 0.27) and the 8 P.M. to 9 A.M. (day 2; R2 = 0.18) intervals. Bromocriptine lowered PRL secretion during both intervals. Secretory rates of growth hormone during these intervals were not affected by 0.1 mg or 0.35 mg mesulergine but were increased during both intervals by the 0.5-mg dose. Neither the secretory rates of thyrotropin in response to TRH nor those of cortisol, luteinizing hormone, or follicle-stimulating hormone were changed by 0.1 or 0.35 mg mesulergine.(ABSTRACT TRUNCATED AT 250 WORDS)

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