Conjugated estrogens and the overnight dexamethasone suppression test

Basal (8:00 AM) serum cortisol levels in peri- or postmenopausal women treated with 0.625 mg daily of conjugated equine estrogens were only slightly higher than pretreatment levels. A 1.25 mg/day dosage resulted in a significant increase in basal serum cortisol levels. In women treated with either dosage, 8:00 AM serum cortisol levels 8 to 10 hours after 1 mg of oral dexamethasone were suppressed to below 5 microgram/100 ml, although there was a significant rise in post-dexamethasone serum cortisol levels in those treated with the higher dosage. It is concluded that while replacement dosages of estrogens increase circulating total serum cortisol levels, they do not interfere with the interpretation of the overnight dexamethasone suppression test.