BIOAVAILABILITY OF NATURAL ESTROGENS IN YOUNG FEMALES WITH SECONDARY AMENORRHEA

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Abstract
The bioavailability of 17 ß‐estradiol valerate, free 17 ß‐estradiol and Premarin was studied in 24 subjects suffering from secondary amenorrhea. 17 ß‐estradiol and estrone were determined by specific radioimmunoassay systems. All estrogens were administered as single oraldoses. Theamounts applied were 2 and 10 mg of 17 ß‐estradiol valerate or equivalent amounts of the free estradiol and Premarin, respectively. No elevations of 17ß‐estradiol serum levels were recorded at the lower dosages, whereas the increases of estrone serum levels were approximately tenfold over basal levels. Similar data were recorded in a group of 3 women with normal cycles after the ingestion of 2 mg of 17ß‐estradiol valerate. All subjects responded to the higher doses of estrogens with a moderate increase of 17ß‐estradiol serum levels, but with much higher elevation of estrone levels. These data suggest a rapid conversion of 17ß‐estradiol into estrone. The biological activity of 2 mg 17ß‐estradiol valerate is discussed on grounds of a possible metabolism of estrone sulfate at the target tissues.