Residual parathyroid function in chronic surgical hypoparathyroidism.

Serial determinations (n = 5-13) of serum ionized calcium and intact parathyroid hormone (PTH) were performed in 12 patients with chronic surgical hypoparathyroidism during 1-2 years of their long-term replacement therapy. Average serum ionized calcium ranged from 1.04 to 1.20 mmol/l (normal range 1.15-1.35 mmol/l) and all had detectable levels of PTH. In hypocalcemic patients a significant inverse relationship between serum concentrations of ionized calcium and PTH was observed. Apparently, the remaining parathyroid glands responded to hypocalcemia by increasing PTH secretion. Thus, the stage is set for a compensatory hypertrophy, but the concentration of PTH remains fairly low for unknown reasons. Maybe treatment with vitamin D would prevent such hypertrophy.