Work

Effect of race, gender and age on intrinsic diurnal variation of serum calcifediol: Insights into vitamin D toxicity

Year: 2025

Type: article

Abstract: Intrinsic diurnal variation of serum calcifediol (25-hydroxyvitamin D 3 ) was evaluated in healthy United States (US) adults by race, gender and age. Eligible participants (18-55 years old, body mass index 18-30 kg/m 2 , body weight ≥50 kg) were enrolled with gender balance into two groups by race: first generation Japanese (n=35) and non-Japanese (n=32). “First generation Japanese” was defined as having Japanese parents and grandparents and residing outside Japan for <5 years without major lifestyle or dietary changes. “Non-Japanese” were of non-Asian descent and included 14 African-Americans, 16 Caucasians and 2 of “Other” race. Vitamin D supplementation during the prior 28 days was an exclusion criterion. Participants were housed for two days in a phase 1 unit shielded from sunlight and fed timed standardized meals devoid of vitamin D. Serum calcifediol, measured by LC-MS/MS on Day 2 at 0, 2, 4, 6, 8, 10, 12, 14, 16, 20 and 24 hours, had a minor circadian rhythm ( p =0.0081) having a midline statistic of rhythm (MESOR) of 21.5 ng/mL, an amplitude of 0.19 ng/mL and an acrophase at 5:24 a.m. Mean inter-participant variation was high (CV of 30.89%) while intra-participant variation was low (5.54%), only nominally exceeding the assay precision (4.10%). No significant differences in rhythmicity were observed between subgroups based on race, gender or age. These data showed that intrinsic diurnal variation of circulating calcifediol is low, suggesting that serum 25D concentrations are highly regulated and that stable circulating levels of 25D reduce the risk of toxicity. • Intrinsic diurnal variation of serum calcifediol was evaluated in healthy US adults • Participants were shielded from sunlight and fed timed meals devoid of vitamin D • Serum calcifediol had a minor circadian rhythm ( p =0.0081) of 0.19 ng/mL amplitude • The observed rhythmicity was did not differ by race, gender or age • Low diurnal variation during repletion appears important to prevent toxicity

Source: The Journal of Steroid Biochemistry and Molecular Biology

DOI: 10.1016/j.jsbmb.2025.106897

Authors: Charles W. Bishop, John Choe, Stephen A. Strugnell, Samir Tabash, Akhtar Ashfaq

Institution: OPKO Health (United States)

Language: English

Topic: Vitamin D Research Studies

Subfield: Pathology and Forensic Medicine

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: hybrid

Estimated APC paid: $3,980