Use of Estrogen-Containing Contraception Is Associated With Increased Concentrations of 25-Hydroxy Vitamin D.

The Journal of clinical endocrinology and metabolism
Q1
Aug 2016
Citations:55
Influential Citations:4
Observational Studies (Human)
80
S2 IconPDF Icon

Enhanced Details

Methods
Design: Cross-sectional observational analysis using linear regression to model season-adjusted serum 25(OH)D. Participants: 1662 African American women aged 23-34 from Detroit, enrolled in a prospective fibroid risk study; intact uterus; no prior fibroids; blood collected at enrollment; 25(OH)D measured; data on contraception use and supplement intake collected; complete covariate data available for 1658.
Intervention
Vitamin D-containing supplements; dosing categories based on intake: low (200 IU/d) or irregular use of a single supplement type; intermediate (201-600 IU/d) or regular use of a single multivitamin; high (≥601 IU/d) or regular use of multiple supplements or a single high-dose vitamin D supplement; cod liver oil provides ~450 IU vitamin D per teaspoon; duration not specified; taken orally; usage patterns (regular vs irregular) assessed via 24-hour questionnaire, 4-week questionnaire, and FFQ.
Results
Current estrogen-containing contraception use is associated with a 20% higher serum 25(OH)D after adjustment for covariates, including vitamin D supplement use. Past estrogen use shows no association. The 20% increase is consistent across estrogen dose levels (10–35 μg ethinyl estradiol) and remains after multiple sensitivity analyses; estrogen may influence vitamin D metabolism, potentially via vitamin D–binding protein. Clinical implications: document exogenous hormone use when interpreting vitamin D status in reproductive-age women and consider adjusting for contraceptive use in vitamin D health research; further studies are needed to elucidate biological pathways.
Limitations
Cross-sectional observational design; potential residual confounding; reliance on self-reported supplement use with imprecise dosing; vitamin D measured by immunoassay, which may underestimate compared with LC-MS; the model explains about a third of the variance; findings may not generalize beyond young African American women in Detroit.

Abstract

CONTEXT Small studies suggest exogenous estrogen may improve vitamin D status, but the etiology is unclear because women who use hormones may make lifestyle choices that differentially affect vitamin D status. OBJECTIVE Our objective was to investi...