PTH and vitamin D deficiency: Furthermore, 1,25(OH)2D stimulates 24‐hydroxylase activity increasing the catabolism of 25OHD to the inactive compound 24,25(OH)2D, thus increasing the risk of developing vitamin D insufficiency with dietary calcium deficiency.8, 23 Raised PTH levels also lead to renal phosphate loss24 and hypophosphatemia that aggravates the bone mineralization defect.