Vitamin-D status and mineral metabolism in two ethnic populations with sarcoidosis

J Investig Med. 2016 Jun;64(5):1025-34. doi: 10.1136/jim-2016-000101. Epub 2016 Apr 6.

Abstract

Vitamin-D insufficiency and sarcoidosis are more common and severe in African Americans (AA) than Caucasians. In sarcoidosis, substrate-dependent extrarenal 1,25-dihydroxyvitamin-D (1,25-(OH)2D) production is thought to contribute to hypercalciuria and hypercalcemia, and vitamin-D repletion is often avoided. However, the anti-inflammatory properties of vitamin-D may also be beneficial. We prospectively examined serum vitamin-D levels, calcium balance, and the effects of vitamin-D repletion in 86 AA and Caucasian patients with biopsy-proven active sarcoidosis from the USA (US) and Italy (IT) in university-affiliated outpatient clinics. Clinical features, pulmonary function, and calciotropic hormones were measured. 16 patients with vitamin-D deficiency and normal serum ionized calcium (Ca(2+)) were treated with oral ergocalciferol (50,000 IU/week) for 12 weeks. Baseline mineral parameters were similar in US (93% AA) and IT (95% Caucasian) patients irrespective of glucocorticoid treatment. Pulmonary dysfunction was less pronounced in IT patients. Nephrolithiasis (in 11% US, 17% IT patients) was associated with higher urinary calcium excretion. Vitamin-D deficiency was not more prevalent in patients compared to the respective general populations. As serum 25-hydroxyvitamin-D (25-OHD) rose postrepletion, serum 1,25-(OH)2D, γ-globulins, and the previously elevated angiotensin converting enzyme (ACE) levels declined. Asymptomatic reversible increases in Ca(2+) or urinary calcium/creatinine (Ca/Cr) developed in three patients during repletion. In conclusion, Caucasian and AA patients show similar calcium and vitamin D profiles. The higher prevalence of hypercalciuria and nephrolithiasis in sarcoidosis is unrelated to endogenous vitamin-D levels. Vitamin-D repletion in sarcoidosis is generally safe, although calcium balance should be monitored. A hypothesis that 25-OHD repletion suppresses granulomatous immune activity is provided.

Keywords: Kidney Calculi; Sarcoidosis; Vitamin D.

MeSH terms

  • Calcium / urine
  • Case-Control Studies
  • Demography
  • Ethnicity*
  • Female
  • Glucocorticoids / therapeutic use
  • Humans
  • Italy
  • Male
  • Middle Aged
  • Minerals / metabolism*
  • Nephrolithiasis / blood
  • Nephrolithiasis / complications
  • Nephrolithiasis / physiopathology
  • Sarcoidosis / blood*
  • Sarcoidosis / drug therapy
  • Sarcoidosis / physiopathology
  • Sarcoidosis / urine
  • United States
  • Vitamin D / analogs & derivatives*
  • Vitamin D / blood

Substances

  • Glucocorticoids
  • Minerals
  • Vitamin D
  • 25-hydroxyvitamin D
  • Calcium