The dual vitamin D pathways: considerations for adequate supplementation

Area of Science:

• Nephrology
• Endocrinology
• Nutritional Science

Background:

• Vitamin D deficiency is common in chronic kidney disease (CKD) and linked to adverse clinical outcomes.
• Impaired kidney function in CKD affects vitamin D metabolism, impacting calcium, phosphorus, and parathyroid hormone (iPTH) levels.
• Traditionally, treatment focused on replacing the active form of vitamin D (calcitriol) due to impaired kidney synthesis.

Purpose of the Study:

• To discuss the dual role of vitamin D in CKD, addressing both its endocrine and newly recognized autocrine functions.
• To highlight the persistent 25(OH)D insufficiency across CKD stages.
• To review current treatment guidelines and therapeutic strategies for vitamin D management in CKD patients.

Main Methods:

• Review of current literature on vitamin D metabolism and its impact on CKD.
• Analysis of clinical outcomes associated with vitamin D status in CKD.
• Discussion of treatment recommendations from organizations like the National Kidney Foundation Kidney Disease Outcomes Quality Improvement.

Main Results:

• Vitamin D insufficiency is prevalent in CKD stages 3, 4, and 5.
• Both endocrine and local (autocrine) vitamin D metabolism influence gene transcription and clinical outcomes.
• Current guidelines recommend ergocalciferol for insufficiency and active vitamin D for deficiency in advanced CKD.

Conclusions:

• Effective management of CKD requires addressing vitamin D deficiency and insufficiency.
• Supplementation strategies must consider both the endocrine and autocrine pathways of vitamin D.
• Optimizing vitamin D therapy can improve clinical outcomes for patients with chronic kidney disease.