Limitations of follicle-stimulating hormone in assessing menopause status: findings from the National Health and Nutrition Examination Survey (NHANES 1999-2000)*.

Objective: We used data from the National Health and Nutrition Examination Survey (NHANES 1999-2000) to: establish new population-based estimates for follicle-stimulating hormone (FSH) and luteinizing hormone (LH); identify factors associated with FSH; and assess its efficacy in distinguishing among women in the reproductive, menopause transition, and postmenopausal stages.

Design: Nationally representative sample of 576 women aged 35 to 60 years examined during NHANES 1999-2000.

Results: Levels of FSH and LH increased significantly with reproductive stage. (Geometric mean FSH levels for successive stages: reproductive, 7.0 mIU/mL, SE 0.4; menopause transition, 21.9 mIU/mL, SE 3.7; and postmenopause, 45.7 mIU/mL, SE 4.3). There was considerable overlap, however, among distributions of FSH by stage. Only age and reproductive stage were significantly associated with FSH in multivariable analysis. FSH cutoff points between the reproductive and menopause transition stages [FSH = 13 mIU/mL, sensitivity 67.4% (95% CI 50.0-81.1), specificity 88.1% (95% CI 81.1-92.8)] and between the menopause transition and postmenopause stages [FSH = 45 mIU/mL, sensitivity 73.6% (95% CI 60.1-83.7), specificity 70.6% (95% CI 52.4-84.0)] were neither sensitive nor very specific.

Conclusions: Age and reproductive stage are the most important determinants of FSH levels in US women; however, FSH by itself has limited utility in distinguishing among women in different reproductive stages.