Hormonal effects of danazol and medical oophorectomy in endometriosis

The hormonal effects of danazol and of a long-acting gonadotropin-releasing hormone analogue (GnRH-a) were studied in women with endometriosis and those with oophorectomy. During danazol treatment, total serum concentrations of estrone and estradiol, and free, dialyzable estradiol were reduced to the low follicular phase range for premenopausal women. Corresponding estrogen levels were suppressed to a significantly greater degree (P less than .02) at the end of GnRH-a administration, to concentrations which were twofold to fourfold lower than with danazol therapy and similar to values in the oophorectomized women. Sex hormone binding globulin was markedly suppressed (P less than .001) throughout danazol treatment, resulting in a threefold elevation (P less than .01) of free testosterone. These data suggest that danazol may affect endometriosis by mechanisms other than by inducing a pseudomenopause. The increased tissue availability of testosterone may be responsible for acne and hirsutism observed in some women during danazol treatment and may inhibit proliferation of the ectopic endometrium. Medical oophorectomy using GnRH-a may have improved effects on endometriosis without the androgenic side effects of danazol.