[Endocrine fertility-restricting factors in clomiphene therapy]

A marked discrepancy between a high ovulation rate (70-80%) and a low pregnancy rate (30-35%) is generally observed during clomiphene therapy in female infertility. Disturbances in follicular maturation, inadequate secretory transformation of the endometrium and influence on the quality of cervical mucus are discussed as cause for this phenomenon. The purpose of this study was to investigate whether changes in endocrine patterns might lead to these changes thus limiting the success of clomiphene therapy. In 7 patients gonadotropins, prolactin, ovarian and adrenal androgens, sexual hormone binding globuline (SHBG) and plasma levels of clomiphene were measured at short intervals during a stimulated cycle. The increase of testosterone and androstendione promoted by clomiphene during the follicular phase is in accordance with previous observations. The decline in SHBG due to an antioestrogenic effect on its hepatic production leads to an additional increase in free, biologically active androgens. These androgens interfere with follicular maturation, causing atresia and premature luteinisation. As a direct effect of clomiphene on the adrenal gland, we observed an elevation of DHEAS. The significance of this finding remains unclear. During the follicular phase prolactin remained suppressed inspite of supraphysiological oestrogen levels. In the late luteal phase the diminished antioestrogenic influence on lactotrophic cells causes a 80% rise in prolactin that in some cases may impair luteal function. The average plasma half-life of clomiphene was found to be 12 days. This is in accordance with the half-life of the closely related compound tamoxifen. Clomiphene, also present in the luteal phase of the cycle, may cause inadequate secretory transformation of the endometrium by blocking endometrial oestrogen receptors.(ABSTRACT TRUNCATED AT 250 WORDS)