Abstract
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.