The effects of transdermal estrogen therapy on bone mass and turnover in early postmenopausal smokers: A prospective, controlled study

Objective The purpose of this study was to investigate whether smoking reduces the effects of transdermal estrogen replacement therapy on bone. Study design One hundred forty-eight women (0.5–5 years after menopause, aged 46–58 years) completed the study. Smokers were assigned randomly to receive either 1.0 mg (n = 32 women) or 1.5 mg (n = 31 women) of transdermal estradiol in gel daily, and nonsmokers (n = 46 women) were assigned to receive 1.0 mg of transdermal estradiol for 2 years. The control group consisted of 17 smokers and 22 nonsmokers. Bone mineral density was measured by dual-energy x-ray absorptiometry. Bone turnover was assessed by measurements of urinary aminoterminal telopeptide of type I collagen and serum aminoterminal propeptide of type I procollagen. Results Lumbar spine bone mineral density increased similarly in smoking (+3.6%) and nonsmoking (+2.6%) estrogen users (P<.0001 to a decrease of 2.5% in the control group). Femoral neck bone mineral density increased 2.2% to 2.4% in smoking and nonsmoking estrogen users but decreased 0.2% in control subjects (P<.05). Urinary aminoterminal telopeptide of type I collagen decreased similarly in all estrogen-using groups (P<.05 to control group), but serum aminoterminal propeptide of type I procollagen decreased more in smoking than in nonsmoking estrogen users (P = .006). Serum 25-hydroxyvitamin D was 20% lower (P = .004) in smokers than in nonsmokers. Conclusion Transdermal estrogen treatment protects smoking women as effectively as nonsmokers from osteoporosis. Smoking worsens the vitamin D state of postmenopausal women.