THE EFFECT OF OESTROGEN ADMINISTRATION ON PLASMA TESTOSTERONE, FSH AND LH LEVELS IN PATIENTS WITH KLINEFELTER'S SYNDROME AND NORMAL MEN

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Abstract
In 6 eugonadal males and 6 patients with Klinefelter's syndrome the effect of increasing amounts of ethinyloestradiol (EE) (15, 30 and 150 μg daily for 7 days) on plasma levels of LH, FSH and testosterone was studied. Control levels of LH and FSH in the Klinefelter patients were significantly higher than in the normal males, whereas plasma testosterone levels were significantly lower. In 3 of the 6 Klinefelter patients plasma gonadotrophin levels were clearly elevated despite normal plasma testosterone concentrations. After EE administration a dose-dependent decrease of plasma FSH and testosterone levels was observed in both the control subjects and the Klinefelter patients, whereas the LH decrease was dose-dependent in the Klinefelter patients, but not however, in the eugonadal males. Despite significant testosterone suppression plasma LH and FSH levels in the Klinefelter patients remained supranormal when compared with the levels of the control subjects. Amounts of EE, roughly equivalent to the physiological oestrogen production (15 μg of EE daily) in men, decreased plasma LH and testosterone levels in the normal males, not however, in the Klinefelter patients. The suppression of plasma testosterone by EE in both the normal subjects and the Klinefelter patients could readily be overcome by exogenous gonadotrophin administration, favouring the concept that the EE induced testosterone decrease is predominantly gonadotrophin mediated. It is concluded that small amounts of oestrogens play a role in the pituitary-gonadal axis in normal males. Although higher doses are needed to modulate this axis in Klinefelter's syndrome, the hypothalamic-pituitary-gonadal feedback in this disorder is still operative, though at a higher setting.

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