Direct feed-back regulation of PTH-secretion by 1,25-dihydroxyvitamin D3 in renal failure: a controlled trial.

To elucidate whether the kidney hormone 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) regulates the secretion of parathyroid hormone (PTH) by direct feed-back, 10 patients with acute oliguric tubulo-interstitial nephropathy were investigated. Serum ionised calcium (Ca++) was kept constant and subnormal by continuous peritoneal dialysis with low Ca++ dialysis fluid. In the control period (24h) PTH was found to be constantly increased. In the treatment period (30h) 1,25(OH)2D3 was injected i.v. every 6 hours. A significant suppression of PTH-levels was observed after a lag-period of 12-18h during stable low Ca++. In the control group PTH remained constantly increased throughout the trial. The data suggest that 1,25(OH)2D3 regulates PTH-secretion in humans with normal parathyroid glands by direct feed-back.