The high Pi together with low Ca2+ and 1,25(OH)2D3 levels are known to stimulate secretion of parathyroid hormone (PTH), with secondary hyperparathyroidism; the accumulating PTH stimulating osteoclastic activity (Brenner and Lazarus 1991; Bover et al. 1999). The gene discussed is PTH; the disease is secondary hyperparathyroidism.