(PO16-88-22) Relationships Between 25-Hydroxyvitamin D, Parathyroid Hormone, and Bone Mass in 4-Year-Old Children in Dhaka, Bangladesh

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Presenting Author(s)

DW

Dante B. Wong, BSc, Immunology & Global Health, Trinity College, University of Toronto
– Research Student, The Hospital for Sick Children, North York, Ontario, Canada

Co-Author(s)

SS

Shaila S. Shaila, MBBS
– Nutrition and Clinical Services Division, International Center for Diarrhoeal Disease Research, Bangladesh, Dhaka, Dhaka, Bangladesh
FF

Farzana Fariha, MBBS
– Nutrition and Clinical Services Division, International Center for Diarrhoeal Disease Research, Bangladesh, Dhaka, Dhaka, Bangladesh
AD

Alison Dasiewicz
– Hospital for Sick Children
JH

Jennifer Harrington
– Women’s and Children’s Health Network and University of Adelaide
AA

Abdullah Al Mahmud, M.S.S, M.M.Sc
– Research Officer, icddr,b, Dhaka, Dhaka, Bangladesh
Steven A. Abrams, MD
– Professor of Pediatrics, Dell Medical School at the University of Texas at Austin, Austin, Texas, United States
TA

Tahmeed Ahmed, MBBS, PhD
– Nutrition and Clinical Services Division, International Center for Diarrhoeal Disease Research, Bangladesh, Dhaka, Dhaka, Bangladesh
DR

Daniel E. Roth, MD, MSc, PhD
– clinician-scientist, Department of Paediatrics, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada
Karen M. O'Callaghan, PhD
– Research Fellow, Centre for Global Child Health, The Hospital for Sick Children, Toronto, Toronto, Ontario, Canada

Disclosure(s):

Dante B. Wong, BSc, Immunology & Global Health, Trinity College, University of Toronto: No relevant financial relationship(s) with ineligible companies to disclose.

Objectives: Elevated serum parathyroid hormone (PTH) concentration was incidentally observed in a high proportion of children in a study in Dhaka, Bangladesh. We explored potential correlates of elevated PTH by estimating the association of PTH with 25-hydroxyvitamin D (25(OH)D) and associations of 25(OH)D and PTH with bone outcomes.

Methods: Data were obtained from the BONe and mUScle health in Kids study (BONUSKids; NCT03537443). Total-body less head (TBLH) bone mineral content (BMC) and areal bone mineral density (aBMD) were measured by dual-energy X-ray absorptiometry (DXA). Serum PTH and 25(OH)D were analyzed by chemiluminescent immunoassay and liquid chromatography-tandem mass spectrometry, respectively. BONUSKids participants (n=642) with DXA, PTH and 25(OH)D data at 4 years were included. Associations between 25(OH)D, PTH and bone outcomes were estimated using unadjusted linear and two-phase linear spline regression models. Model fit was compared using AIC.

Results: Among the 534 children who met inclusion criteria, 43% were vitamin D deficient ( < 30nmol/L) and 30% had PTH > 6.9pmol/L. A non-linear inverse relationship was observed between 25(OH)D and PTH. Model fit was optimized with an inflection point at 25nmol/L, above which the association attenuated ( < 25nmol/L: -0.16pmol/L per 1nmol/L change in 25(OH)D [95%CI -0.23, -0.10]; ≥ 25nmol/L: –0.02pmol/L [95% CI -0.04, -0.008]. 25(OH)D was positively linearly associated with TBLH BMC (0.39g per 1nmol/L change in 25(OH)D [95%CI 0.10: 0.69]) and aBMD (0.0004g/cm² per 1nmol/L change in 25(OH)D [95% CI 0.0002, 0.0006]). There was no significant association between PTH and TBLH BMC. The non-linear association between PTH and TBLH aBMD was negative at PTH > 4pmol/L ( < 4pmol/L: 0.002g/cm² per 1pmol/L change in PTH [95% CI –0.006, 0.01], ≥ 4pmol/L: -0.002g/cm2 [95% CI -0.0038, -0.0002]).

Conclusions: The non-linear inverse association of PTH with 25(OH)D supports the hypothesis that vitamin D deficiency contributed to elevated PTH in this population. Although 25(OH)D was associated with bone outcomes, the magnitude of the association was similar at 25(OH)D concentrations below and above 25nmol/L. PTH was inconsistently associated with bone outcomes, suggesting single measurements of PTH may not be a useful marker of bone health in this setting.

Funding Sources: Canadian Institutes of Health Research