Background: Cortisol within the normal range has been associated with reduced bone density in the elderly, but little is known about this relationship in healthy young women.
Purpose: The purpose of this study is to assess whether 24-h urinary free cortisol excretion (UFC) is related to bone density in 132 healthy, non-obese, regularly menstruating women, aged 19-35.
Method: Participants completed questionnaires (food frequency, demographics, physical activity, dietary restraint, perceived stress, and daily stress) and a 24-h urine collection. UFC was determined by high-throughput liquid chromatography and tandem mass spectrometry. Anthropometrics were completed and a dual energy X-ray absorptiometry scan measured areal bone mineral density (aBMD, g/cm(2)) and bone mineral content (BMC, g) at the lumbar spine (L1-4), hip, and total body (TB) as well as total body lean (LBM) and fat mass.
Results: aBMD and BMC were significantly positively associated with height, LBM, physical activity, calcium intake, and duration of previous oral contraceptive use (except L1-4) and negatively with perceived stress. UFC was not correlated with any measured variables except urine volume (r = 0.17, p = 0.046). After adjusting for urine volume, height, LBM, ethnicity, and prior oral contraceptive use, UFC was significantly inversely associated with TB BMC (r = -0.30, p < 0.001) and aBMD (r = -0.27, p = 0.003), L1-4 aBMD (r = -0.19, p = 0.035) and BMC (r = -0.18, p = 0.049), and hip BMC (r = -0.23, p = 0.011). Further adjustment for sport activity, calcium intake and perceived stress did not change these relationships meaningfully except that L1-4 became nonsignificant (p < 0.07).
Conclusion: Cortisol within the normal range appears to have a minor negative influence on bone density in healthy young women.