Similarly, low blood 25-hydroxyvitamin D (25(OH)D) levels, a marker for overall vitamin D status, can be a risk factor for subsequent fractures.3,8,9,13 Vitamin D deficiency and insufficiency are reported to be very common in children.3,8,9 Vitamin D deficiency leads to negative calcium balance, increasing parathyroid hormone in severe deficiencies and causing reabsorption of bone.3 The physiologic consequence is low bone mineral density and quality compromising bone strength. This evidence concerns the gene PTH and vitamin D deficiency.