Vitamin D for glycemic control: A multicenter, double-blind, randomized, placebo-controlled trial in adults with cystic fibrosis.

Individuals with cystic fibrosis (CF) often incur damage to pancreas tissue due to a dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR) protein, leading to altered chloride transport on epithelial surfaces and subsequent development of cystic fibrosis-related diabetes (CFRD). Vitamin D deficiency has been associated with the development of CFRD. The purpose of this study was to examine the impact of a high-dose bolus of cholecalciferol (vitamin D3) on glycemic control. This was a secondary analysis of a multicenter, double-blind, randomized, placebo-controlled study in adults with CF hospitalized for an acute pulmonary exacerbation (APE). Glycemic control was assessed by hemoglobin A1c (HbA1c) and fasting blood glucose levels before and 12 months after the study intervention. Within 72 hours of hospital admission, participants were randomly assigned to a single dose of oral vitamin D3 (250,000 IU) or placebo, and subsequently, received 50,000 IU of vitamin D3 or placebo every other week, beginning at month 3 and ending on month 12. Fifty of the 91 participants in the parent study were eligible for the secondary analysis. There were no differences in 12-month changes in HbA1c or fasting blood glucose in patients randomized to vitamin D or placebo. A high-dose bolus of vitamin D3 followed by maintenance vitamin D3 supplementation did not improve glycemic control in patients with CF.