Haptoglobin genotype as a risk factor for postmenopausal osteoporosis

Editor—Some epidemiological and experimental data have shown a correlation between iron metabolism and calcium, phosphate, and magnesium turnover.1 2 In particular, previous reports have shown that iron availability can play a fundamental role in bone metabolism and that iron depletion can lead to bone demineralisation. For example, in patients who underwent gastrectomy3-5 or in rats treated similarly,6 osteoporosis was accompanied by laboratory and clinical signs of iron deficiency and was prevented by the administration of fructo-oligosaccharides, a substance that promotes iron absorption from the gut. In oophorectomised rats (a condition mimicking the oestrogen levels commonly found in the menopause), a wide range of cells, including osteoblasts, displayed a reduced number of transferrin receptors and hence a reduced iron uptake.7 In humans, it has been assessed that out of 14 nutrients tested (including calcium), iron was the best positive predictor of BMD in the femoral neck,8 and furthermore a negative correlation between ascorbic acid content of the diet and osteoporosis has been found9 10; it is notable that ascorbic acid in the diet affects iron absorption increasing it by a factor of 2-3. A severe nutritional iron deficiency anaemia provokes significant alterations in the metabolism of calcium, phosphorus, and magnesium in rats with a noticeable degree of bone demineralisation, even in the presence of normal serum levels of calcium, phosphorus, and magnesium.1 On the basis of the above evidence, we searched for a genetic …