Clearance of 25-hydroxyvitamin D3 During Vitamin D3 Supplementation

Clearance of 25-hydroxyvitamin D3 During Vitamin D3 Supplementation

The goal of this study is to determine how 25(OH)D3 clearance is affected by vitamin D3 supplementation using a gold standard pharmacokinetic approach.

We expect that this study will enhance interpretation of available diagnostic tests, inform the results of ongoing large clinical trials of vitamin D supplements, and help develop new strategies to target vitamin D to improve health.

Inclusion Criteria:

• Successful prior completion of related protocol CLEAR (NCT02937350) or CLEAR-CF (NCT03104855)
• Age ≥ 18 years
• Self-reported race Caucasian, African American, or African

Exclusion Criteria:

• Primary hyperparathyroidism
• Gastric bypass
• Tuberculosis or sarcoidosis
• Current pregnancy
• Child-Pugh Class B or C cirrhosis (i.e. cirrhosis with ascites, hepatic encephalopathy, bilirubin >=2 mg/dL, serum albumin <=3.5 g/dL, or PT >= 4 seconds)
• History of kidney transplantation (unless failed transplant now treated with hemodialysis)
• Use of 1,25(OH)2D3 or an analogue, calcimimetics, or medications known to induce CYP24A1 within 4 weeks (wash-out allowed)
• Serum calcium > 10.1 mg/dL
• Hemoglobin < 10 g/dL