What form of Vitamin D is measured in patients with End-Stage Renal Disease (ESRD) undergoing dialysis?

From the Guidelines

In patients with End-Stage Renal Disease (ESRD) undergoing dialysis, 25-hydroxyvitamin D (25(OH)D) levels are typically measured to assess vitamin D status. This is because 25(OH)D is the main circulating form of vitamin D and reflects both dietary intake and skin synthesis 1. While 1,25-dihydroxyvitamin D (calcitriol) is the active form, it's not routinely measured for vitamin D status assessment because it has a short half-life and levels can be normal or even elevated in vitamin D deficiency due to secondary hyperparathyroidism. Some key points to consider when measuring vitamin D levels in ESRD patients include:

• The prevention and treatment of vitamin D insufficiency in patients with CKD Stages 3 and 4 can reduce the frequency and severity of secondary hyperparathyroidism 1
• In patients with more advanced CKD (Stage 5) and in dialysis patients, it is not established that nutritional "replacement" with vitamin D will be effective since the ability to generate adequate levels of 1,25(OH)₂D₃ is markedly reduced or is unlikely 1
• Many dialysis patients have low levels of 25(OH)D due to reduced exposure to sunlight, low dietary intake of vitamin D, and impaired skin synthesis of vitamin D 1
• Supplementation with ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3) may be recommended for dialysis patients with low 25(OH)D levels, typically starting at 50,000 IU weekly for 8-12 weeks followed by maintenance therapy of 1,000-2,000 IU daily 1
• Regular monitoring of calcium, phosphorus, and PTH levels is essential when supplementing vitamin D in dialysis patients to avoid complications like hypercalcemia and vascular calcification 1

From the FDA Drug Label

The mean elimination half-life of 1α,25-(OH)2D 2 in patients with end-stage renal disease (ESRD) and in healthy volunteers appears to be similar following an oral dose. Hemodialysis causes a temporary increase in 1α,25- (OH) 2D 2 mean concentrations, presumably due to volume contraction. 1α,25-(OH) 2D 2 is not removed from blood during hemodialysis.

The form of Vitamin D measured in patients with End-Stage Renal Disease (ESRD) undergoing dialysis is 1α,25-(OH)2D 2 2.

From the Research

Forms of Vitamin D in ESRD Patients

• The two main forms of Vitamin D relevant to patients with End-Stage Renal Disease (ESRD) undergoing dialysis are:
  • 25-hydroxyvitamin D, which is the less active form of vitamin D 3
  • 1,25-dihydroxyvitamin D (calcitriol), which is the activated form of vitamin D 3, 4, 5

Measurement and Relevance

• In patients with ESRD, both 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels are often measured to assess vitamin D status 3, 5
• 1,25-dihydroxyvitamin D is particularly important in ESRD patients, as it plays a crucial role in regulating parathyroid hormone (PTH) levels and preventing secondary hyperparathyroidism 3, 4, 5

Clinical Implications

• Activated vitamin D (1,25-dihydroxyvitamin D) therapy is commonly used in ESRD patients to decrease PTH levels and prevent secondary hyperparathyroidism 3, 4, 5
• However, vitamin D therapy can also have potential side effects, such as hypercalcemia and hyperphosphatemia 4, 6
• The optimal form and dosage of vitamin D therapy in ESRD patients is still a topic of debate and requires further research 3, 4, 5, 6