A comparison of parathyroid-gland function in haemodialysis patients with different forms of renal osteodystrophy

Parathyroid function was studied in three different histological forms of renal osteodystrophy: osteitis fibrosa (OF), low-turnover aluminium-associated bone disease (LTAABD), and aplastic bone disease without aluminium (ABD). Parathyroid function was determined by the evaluation of the sigmoidal parathyroid hormone-(PTH)-calcium curve, which was obtained by the performance of a reduced calcium and an increased calcium haemodialysis. Parameters of the sigmoidal PTH-calcium curve evaluated included maximally stimulated (PTH(Max)) and inhibited (PTH(Min)) PTH, the set point of calcium for PTH (ICA₅₀), defined as the ionised calcium concentration at which PTH(Max) was reduced by 50%, the ratio of basal PTH to maximally stimulated PTH (PTH(Base): PTH(Max)), the ionised calcium concentration at which basal (ICA(Base)), maximally stimulated (ICA(Max)), and maximally inhibited (ICA(Min)) PTH values were observed, and the slope of the PTH-calcium curve. Both PTH(Max) and PTH(Min) were greater in OF than the other two groups (P50 and the ICA(Max) were greater (P50 and ICA(Max) indicates a shift of the PTH-calcium curve to the right; and (c) the steeper slope of the PTH-calcium curve (OF versus LTAABD) indicates that the sensitivity of parathyroid cells was enhanced.