VDR and secondary hyperparathyroidism: In most cases the disease associated with this VDR gene is transmitted in an autosomal recessive manner (both alleles must be altered) and patients present severe hypocalcemia and secondary hyperparathyroidism, with elevated serum levels of 1,25-dihydroxyvitamin D. However, some changes in the heterozygous state have also been described as disease causing [24].