Endogenous estradiol and progesterone concentrations in smokers on oral contraceptives

The simultaneous effects of cigarette smoking and oral contraceptives on serum estradiol and progesterone levels were investigated in 114 premenopausal women. Serum 17β-estradiol and progesterone levels were measured by radioimmunoassay. In smokers, estradiol and progesterone levels were significantly lower (p < 0.025). In smokers using oral contraceptives, estradiol and progesterone levels were the lowest (p < 0.001 and p < 0.01, respectively). The findings suggest that smoking and oral contraceptives independently lower serum estradiol and progesterone concentrations in premenopausal women and that the effects may be additive.