Effects of RU16117, an orally active weak oestrogenic compound, in postmenopausal women

Daily oral administration of 1, 3 or 10 mg of RU16117 (11 alpha-methoxy ethinyl oestradiol) to normal postmenopausal women led to a progressive decrease of basal serum LH levels to 60.4 +/- 17.0, 35.1 +/- 9.1 and 20.1 +/- 2.8% of control (pretreatment values, P less than 0.01), respectively, after 4 wk of drug administration. Although the pattern was similar, the inhibitory effect of RU16117 was even more pronounced on FSH than LH levels: a 50% decrease of basal LH and FSH levels was obtained at the daily 1.8 and 1.2 mg doses of RU16117, respectively. No significant change of basal serum gonadotrophin levels was observed with the daily 0.3 mg dose. Administration of 1 mg of RU16117 every second day or 10 mg once a week led to a relatively small but significant (P less than 0.05) 20--25% decrease of basal serum LH levels after 4 wk of treatment in four out of five women. While daily 0.3 and 1.0 mg doses of RU16117 had no significant effect on the LH response to 100 microgram LHRH, the 3.0 mg dose delayed the response up to 90 min. The 10 mg dose, on the other hand, led to a markedly delayed and reduced response. Treatment for the same period (4 wk) with 1 mg RU16117 every second day or 10 mg once a week led to a small (20--25%, P less than 0.05) inhibition of the LH response to LHRH. At the dose of 10 mg once a week, RU16117 had no or minimal effect on endometrial histology. Since RU16117, an orally active weak oestrogenic compound, has been shown to have anticarcinogenic activity in the rat, the present findings suggest that this new steroid could be useful for the treatment of climacteric symptoms.