Effects of aminoglutethimide on adrenal steroid secretion.

Effects of various doses of aminoglutethimide (AG) alone upon adrenal steroidogenesis were studied in normal postmenopausal women, whereas the effects of combined treatment with aminoglutethimide in variable doses together with 40 mg of hydrocortisone were studied in postmenopausal women with advanced mammary cancer and compared to effects of treatment with cortisol alone. Despite the well known inhibitory effect of AG on cortisol biosynthesis, plasma cortisol levels were unaffected by AG in doses of 150-1000 mg/d, probably due to a compensatory increase in ACTH in subjects with an intact pituitary-adrenal axis. The aromatase system appeared to be very sensitive to inhibition by AG, a clearcut inhibition being shown at doses as low as 150 mg/d. Evaluated from the ratio of plasma oestrone (E1) to plasma androstenedione (AN), treatment with AG at a dose of 150 mg/d appeared to reduce the aromatase activity to 33% of the basal value; 250 mg/d resulted in a reduction to 20% and 1 g/d to 5% of basal values. Whereas AG at 150 mg/d did not appear to affect 11 beta-hydroxylase, the latter was clearly inhibited by 250 mg/d and even more so by 1000 mg/d, as indicated by the increase in plasma 11-desoxycortisol and 17-OH progesterone (17-OHP) levels. Due to the increase of the latter, their biosynthetic precursor, AN and to a lesser degree testosterone (TS) levels increased significantly during AG treatment at a dose of 250 or 1000 mg/d. delta 5 steroid levels remained practically unchanged, probably because 11-(as well as the 21-) hydroxylation concerns essentially the delta 4 pathway. During combined treatment with 500-1000 mg/d of AG and cortisol 40 mg/d, AN and TS were significantly higher than during treatment with cortisol alone, suggesting that cortisol had not completely blocked ACTH secretion. E1 and E2 levels were however lower than during treatment with cortisol alone, a consequence of the inhibition of the aromatase activity. Although at a dose of 500-1000 mg/d AG is a highly effective aromatase inhibitor, oestrogen levels during treatment with AG with or without concomitant administration of cortisol are still significantly different from zero. Therefore if one aims at complete elimination of any oestrogen effect, addition of an antioestrogen to AG treatment may be required.