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Progesterone is known to prevent labour at term in domestic animals, but its effect in primates is uncertain. 5 alpha-reduced progesterone metabolites are more potent central nervous system depressants than progesterone is itself. Progesterone and its 5 alpha-reduced metabolites also relax pregnant rat myometrium in vitro. The serum concentration of the initial 5 alpha-reduced metabolite, 5 alpha-pregnane-3,20-dione, is high during pregnancy, but decreases significantly prior to parturition. The next metabolite, 5 alpha-pregnane-3 alpha-ol-20-one, has anaesthetic properties in human beings. The purpose of this study was to ascertain whether these progesterone metabolites also suppress contracting human uterine muscle at term. An in vitro model was devised. Strips of human myometrial muscle were mounted in organ chambers and after regular contractions had become established, the strips were superfused with progestin solutions. The progestins were dissolved in the buffer using an ultrasound bath. Progesterone, used as reference substance, slightly reduced the measured amount of muscular work performed per contraction, recordable after 18 min of exposure (p less than 0.05). Similar results have been reported previously in the literature; 5 alpha-pregnane-3 alpha-ol-20-one showed the same tendency though not significant at the 5% level. 5 alpha-pregnane-3,20-dione evidently reduced the contraction frequency after 10 min of exposure (p less than 0.05). None of the substances affected the duration of the contraction. These 5 alpha-reduced progesterone metabolites are thus not potent inhibitors of contracting human term myometrium in vitro.

Two groups of postmenopausal women with climacteric symptoms were investigated during unopposed cyclic replacement therapy with tablets of micronized 17P-oestradiol (2 mg daily) and percutaneous 17P-oestradiol (3 mg daily). The resultant serum levels of 17P-oestradio1, total oestrone and three liver proteins: sex-hormone-binding globulin (SHBG), pregnancy-zone protein (PZP) and caeruloplasmin were followed. In both groups similar levels of serum 17P-oestradiol (ca 500 PM) were recorded, while the increase of total oestrone was much more pronounced after oral treatment. During oral therapy the serum levels of all three proteins showed a marked increase after the first cycle and the levels then remained stable. In contrast, protein levels were unchanged during percutaneous treatment, in spite of the highly increased concentrations of circulating oestrogens. This observation is important as several side-effects of oestrogen therapy may be related to liver function.

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