Vitamin-D Status and Mineral Metabolism in Two Ethnic Populations with Sarcoidosis

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 (Ca2+) 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 Ca2+ 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.

Diagnosis and Detection of Sarcoidosis. An Official American Thoracic Society Clinical Practice Guideline

“…Patients who require calcium repletion are at risk for hypercalciuria and/or hypercalcemia, and need to be monitored closely, because the effects of calcium and vitamin D supplementation are complex. Studies have reported a small, but significant, increase in hypercalcemia with calcium and vitamin D supplementation (136)(137)(138), with another finding that withdrawal of calcium and vitamin D supplementation improved the hypercalcemia (127). Whereas hypercalcemia caused by vitamin D supplementation did not cause sustained renal damage, vitamin D supplementation was shown to be ineffective in terms of improved bone health or other benefits (123) Rationale for question.…”

ERK1,2 Signalling Pathway along the Nephron and Its Role in Acid-base and Electrolytes Balance

“…Parathormone (PTH) and Vitamin D are known to control Ca +2 and phosphate (PO 4 −2 ) homeostasis through direct actions on the PT and the DCT [53,54]. Ko and coworkers showed that PTH inhibits NCC activity via the Ras/ERK1,2 pathway [53].…”

Serum and urinary calcium level in Latvian patients with sarcoidosis

“…Nephrolithiasis is a common renal manifestation of sarcoidosis. In a recent study, calcium in urine was higher in patients with nephrolithiasis, but serum 25-hydroxycholecalciferol and calcitriol did not correlate with urine calcium levels [16]. Coexistence of active sarcoidosis and primary hyperparathyroidism can be a diagnostic challenge, as hypercalcemia can coincide with normal or decreased parathyroid hormone values [17].…”

“…Saidenberg-Kermanac’h et al [1] in 2014 reported that low level of 25-hydroxycholecalciferol is negatively correlated with the activity of sarcoidosis. However, a recent study that compared vitamin D status and calcium metabolism in two ethnic groups of patients (Caucasian patients in Italy and African American patients in the USA) concluded that the risk of vitamin D deficiency is not increased in sarcoidosis patients in comparison with the general population, nor there was found a difference in vitamin D and calcium metabolism between the two ethnic populations [16].…”