Vitamin D metabolism and osteomalacia in patients with fractures of the proximal femur.

A high frequency of histological osteomalacia (25 per cent) was seen in patients with fractures of the proximal femur. No correlation was found between the levels of circulating 25-hydroxyvitamin D (25-OHD) or 1,25-dihydroxyvitamin D (1,25-(OH)2D) and the bone histomorphometric changes.The serum 25-OHD levels were normal, which excludes a dietary vitamin D deficiency or a reduced hepatic hydroxylation of the vitamin. The mean serum 1,25-(OH)2D concentration was significantly reduced in the whole patient group, but surprisingly the levels were normal in those with histological osteomalacia, indicating that an impaired conversion of 25-OHD to 1,25-(OH)2D was not the primary cause of the bone disease. A reduced sensitivity to 1,25-(OH)2D might be a possible explanation for the osteomalacia.