FSH levels in relation to hysterectomy and to unilateral oophorectomy

Objective: To examine the association between hysterectomy, unilateral oophorectomy, and ovarian status, measured by FSH concentrations, in women aged 35-49 years. Methods: From the National Health and Examination Survey III, 1716 women aged 35-49 years were studied. Information on menopausal status, surgical history (hysterectomy, single or bilateral oophorectomy), smoking, and other characteristics was collected in a structured interview, height and weight were measured, and one blood sample was collected. We used logistic regression to analyze FSH concentration in relation to hysterectomy and oophorectomy, controlling for age, ethnicity, body mass index, smoking, education, nulligravidity, and exercise. Results: Hysterectomy with unilateral oophorectomy was associated with an increased prevalence of elevated FSH (above 20 IU/L) (adjusted odds ratio [OR] 2.4, 95% confidence interval [CI] 1.3, 4.6) compared with women who had not had hysterectomies or oophorectomies. Among women with two ovaries, hysterectomy was associated with increased prevalence of elevated FSH (adjusted OR 1.5, 95% CI 1.0, 2.5). As a comparison of the effect size, the observed association between hysterectomy and elevated FSH was smaller than the association between FSH and current smoking (OR 2.0), a factor associated with a 1-2 year decrease in mean age at natural menopause. Conclusion: Although the differences in FSH levels were small, there was evidence of elevated FSH in women who have had hysterectomies, even if at least,one ovary remained, (Obstet Gynecol 1999;94:969-72. (C) 1999 by The American College of Obstetricians and Gynecologists.).