The relationship between 24-h urinary cortisol and bone in healthy young women.
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.


OBJECTIVE
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.


METHODS
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).


CONCLUSIONS
Cortisol within the normal range appears to have a minor negative influence on bone density in healthy young women.
Bedford
Jennifer L
JL
Human Nutrition, The University of British Columbia, 2205 East Mall, Vancouver, BC, V6T 1Z4, Canada.
Barr
Susan I
SI
D000328:Adult; D001823:Body Composition / Q000502:physiology; D001827:Body Height / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D015519:Bone Density / Q000502:physiology*; D003278:Contraceptives, Oral, Hormonal / Q000378:metabolism; D004435:Eating; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000652:urine*; D009043:Motor Activity; D011795:Surveys and Questionnaires; D055105:Waist Circumference / Q000502:physiology; D055815:Young Adult
D003278:Contraceptives, Oral, Hormonal; D006854:Hydrocortisone