PULSE AMPLITUDE AND FREQUENCY-MODULATION OF PARATHYROID-HORMONE IN PRIMARY HYPERPARATHYROIDISM

Pulsatile secretion of PTH in human subjects has been described recent ly. However, the pattern of PTH secretion in primary hyperparathyroidi sm (pHPT) remains to be characterized. In this study intact PTH was me asured in 9 female patients with pHPT. As a control group we present d ata from 10 postmenopausal women. In addition to parameters of calcium metabolism and bone mass, PTH was measured in samples drawn over 4 or 6 h every 2 min by central venous blood sampling. The mean intact PTH concentration was 39.0 +/- 20.3 ng/L in healthy women and 193.2 +/- 1 27.9 ng/L in female patients with pHPT (P < 0.01). Pulse rhythm analys is showed significant differences between both groups for total PTH se cretion per h (patients, 1196.4 +/- 485.3 ng/L; control group, 271.7 /- 132.2 ng/L), basal PTH secretion per h (patients, 852.4 +/- 459.1 n g/L; control group, 185.6 +/- 126.1 ng/L), and average PTH secretion p er pulse (patients, 112.6 +/- 54.8 ng/L; control group, 23.2 +/- 7.1 n g/L). Both patients and control subjects had, on an average, five puls es per h,and the pulsatile secretion accounted for about 50% of the to tal secretion. Differences in power spectrum analysis were consistent with these findings. The cross-correlation of PTH and calcium indicate s an impaired feedback regulation in pHPT. PTH secretion in female pat ients with pHPT results from both an increased basal secretion and an increased amplitude of PTH pulses. Other features of secretion are the same as those in normal women. Feedback regulation of PTH and calcium is impaired in pHPT.