Endocrine Abstracts

Introduction: The uncertainty surrounding the optimal dose to rectify severe vitamin D deficiency (VDD) necessitates further investigation.

Aim: To review and analyze various vitamin D (VD) supplementation doses, durations, and their effects on 25-hydroxyvitamin D (25OHD) levels, along with their biochemical and clinical outcomes, in the management of VDD.

Methods: We reviewed intervention studies targeting VDD from databases (PubMed, Google Scholar, ResearchGate, and Scopus, focusing on studies published after 2010.

Results: Twenty-two studies were reviewed. Comparing different regimens, VD3 showed superiority over VD2 in doses of 1600 IU and 50 000 IU once daily and once monthly, respectively, at the conclusion of a year. For adults, the widely adopted ‘loading dose’ approach (50 000 IU VD orally once weekly for 2–3 months) indicated a minimum cumulative dose of 600 000 IU for achieving an end-of-treatment 25OHD level exceeding 30 ng/ml. The average daily dose for significant serum 25OHD increase was 4707 IU/day for a large adult population. A predictive equation for VD dosage suggested that the required dose =[(8.52 – Desired change in serum 25OHD level) +(0.074 × Age) - (0.20 × BMI) +(1.74 × Albumin concentration) - (0.62 × Starting serum 25OHD concentration)] / (−0.002). Another simplified equation for adults proposed a loading dose formula: IU =40 × (75 nmol/l – serum 25OHD) × body weight. Two prospective studies involving infants and adolescents who received intramuscular cholecalciferol injections (10 000 IU/kg) demonstrated significant improvements in biochemical and clinical outcomes, with most achieving serum 25OHD levels ≥ 20 ng/ml three months post-injection. In older women, a daily oral dose of 50 000 IU calciferol for ten days elevated 25OHD from 8 ng/ml to 21 ng/ml. Patients treated with cumulative doses of 100 000, 150 000, and 200 000 IU displayed corresponding increases in mean serum 25OHD levels. Reviews of 49 and 76 trials indicated an increase of 2 ng/ml per 100 IU/d of ingested VD and an average rise of 0.78 ng/ml per 40 IU of VD3 supplement daily, respectively. In a study with sixty adolescents, those receiving 300 000 IU VD3 followed by 50 000 IU monthly, or 100 000 IU every three months had higher 25OHD levels (30 ng/ml) than those receiving 50 000 IU every three months or 100 000 IU every three months (15 ng/ml).

Summary: Utilizing a megadose oral or intramuscular loading regimen of VD (300 000 IU, 10 000 IU/kg) followed by daily doses of 1000–2000IU or 50 000IU monthly seems effective for managing severe VDD.