Vitamin D Homeostasis in Sarcoidosis

Vitamin D Homeostasis in Sarcoidosis

This study evaluates the relationship between vitamin-D status and severity of sarcoidosis, and the effects of vitamin-D repletion in vitamin-D insufficient patients with sarcoidosis. Half the patients with sarcoidosis who are vitamin-D insufficient will receive standard vitamin-D supplementation via standard regimen while the other half will receive a placebo. Sarcoidosis patients who are vitamin-D sufficient will also act as controls.

Sarcoidosis is a multi-system inflammatory disease characterized by T-helper lymphocyte hyperactivity leading to granulomatous inflammation. The granuloma cells autonomously convert 25-hydroxy-vitamin-D (25OHD) to the active metabolite 1,25-dihydroxy-vitamin-D (1,25OH2D) independent of normal feedback control but dependent on substrate (25OHD) concentration.

Circulating 1,25OH2D exerts both anti-inflammatory and mineral metabolic actions. Deficiency of 25OHD limits substrate-dependent 1,25OH2D synthesis, diminishes anti-antigenic innate immunity and augments pro-inflammatory adaptive immunity. Thus, low vitamin-D stores could aggravate sarcoid inflammation while repletion of vitamin-D stores could mitigate inflammation in sarcoidosis.

Inclusion Criteria:

• Stable medical condition defined as no hospitalization or emergency room visit in the previous 3 months
• No evidence of active pulmonary or systemic infection
• No other active inflammatory disease,
• No active malignancy.
• Normal serum ionized calcium level

Exclusion Criteria:

• Hospitalization or emergency room visit in the previous 3 months
• Evidence of active pulmonary or systemic infection
• Evidence of active other inflammatory disease
• Evidence of active malignancy
• Elevated serum ionized calcium level