Effect of vitamin D3 treatment on bone density in neurofibromatosis 1 patients: A retrospective clinical study

Abstract Objectives We have previously demonstrated reduced bone density and an increased incidence of 25-hydroxy vitamin D 3 (25-OH D 3 ) deficiency in adults with neurofibromatosis 1 (NF1) compared to healthy controls. Vitamin D 3 is a cheap, safe, and effective supplement in the general population, but its value in NF1 patients has not been demonstrated. This study investigates the therapeutic potential of oral vitamin D 3 on bone mineral density (BMD) in NF1 patients with vitamin D 3 deficiency. Methods We measured serum 25-OH D 3 , parathyroid hormone, calcium, and bone alkaline phosphatase concentrations, urinary deoxypyridinoline concentrations, and BMD in 35 adults with NF1. Nineteen patients received vitamin D 3 supplementation for 2 years, six patients received supplementation for 1 year and 10 patients received no supplementation. Supplementation was administered in a dose that maintained the serum 25-OH D 3 level above 30 μg/l. BMD was measured again at 1 and 2 years, and biochemical assessments of bone metabolism were measured at least every half year during therapy. Results Treated subjects had significantly reduced loss of BMD, as measured by T score at the hip ( p  = 0.011) and lumbar spine ( p  = 0.022). The effect on hip BMD was apparent at 1 year in comparison to baseline ( p  = 0.02) and was greater at 2 years in comparison to measurements at 1 year ( p  = 0.02). Conclusions Vitamin D 3 supplementation improves BMD in adult NF1 patients. Further studies are needed to elucidate the mechanisms responsible for reduced BMD in NF1 patients.