Presence of positive feedback between oestrogen and LH in patients with Klinefelter's syndrome, and Sertoli-cell-only syndrome.

In five adult patients with Klinefelter's syndrome and two with Sertoli-cell-only syndrome, exogenous administration of 17 beta-oestradiol, resulting in a sustained and prolonged elevation of circulating oestrogen levels, had a biphasic effect on LH release. After an initial decrease, a dramatic rise in peripheral levels of LH (positive feedback) was observed in all patients. The timing and magnitude of the induced LH surge was similar to that observed in postmenopausal women after administration of large doses of Ethinyloestradiol. A similar positive feedback effect on the secretion of FSH could not be demonstrated. In two patients with the Sertoli-cell-only syndrome, oestrogen treatment induced marked variations in serum testosterone levels, which appeared to be related to the LH changes. Similar changes were not present in patients with Klinefelter's syndrome, indicating a decrease in the sensitivity of the testicular Leydig cell. These experiments demonstrate that positive feedback between oestrogen and luteinizing hormone is present in the adult human male.