[Rickets resistant to calcitropic hormones]

Resistance to vitamin D is known since a long time but was erroneously ascribed to phosphate deficiency (phosphate diabetes or deficiency in tubular phosphate reabsorption). True vitamin D resistance can either be due to lack of the receptor itself or to structural abnormality in the hormone -or DNA-binding site of the receptor whereas in a few cases post-receptor resistance has been documented. In view of the therapeutic consequences, diagnosis of vitamin D resistance is needed in every case of rickets not due to simple vitamin D deficiency. Such cases can be easily recognized by normal 25-hydroxyvitamin D concentration in the presence of biochemical, radiological or/and histological signs of rickets.