The non-linear associations of serum follicle-stimulating hormone levels with bone mineral density and the risk of osteoporosis during menopausal transition: an analysis of National Health and Nutrition Examination Survey data.

Purpose: To explore the non-linear associations of serum FSH levels with BMD and the risk of osteoporosis in pre- and postmenopausal women.

Methods: Data analyzed in this study were derived from the National Health and Nutrition Examination Survey (NHANES) III and the NHANES from 1999 to 2002. Women aged from 35 to 60 years with complete data of serum FSH levels and BMD were eligible. Serum FSH levels were assayed using the Microparticle Enzyme Immunoassay technology. Lumbar spine and femur neck BMD were measured using a dual energy X-ray absorptiometry. Osteoporosis was assessed according to BMD of lumbar spine, total femur, and femur neck.

Results: This study included 3743 women. A significant non-linear association of serum FSH levels with lumbar spine BMD was observed only in postmenopausal women (P for non-linear association = 0.013) but not in premenopausal women (P for non-linear association = 0.092). The results of femur neck BMD were comparable with those of lumbar spine BMD. Meanwhile, there was significant non-linear association of serum FSH levels with the risk of osteoporosis only in postmenopausal women (P for non-linear association = 0.050).

Conclusion: Non-linear associations of serum FSH levels with BMD at lumbar spine and femur neck were observed only in postmenopausal women. Meanwhile, serum FSH levels were non-linearly associated with the risk of osteoporosis in postmenopausal women.