PULSATILE SECRETION OF PARATHYROID-HORMONE IN PATIENTS WITH CHRONIC-RENAL-FAILURE

Peripheral blood concentration of intact PTH is a simple assay very useful in the diagnosis and evolutive control of secondary hyperparathyroidism in patients with chronic renal failure. Episodic secretion of PTH in CRF patients would affect interpretation of single random determinations. To evaluate the secretory pattern of intact PTH we sampled peripheral blood at 6-min intervals for 60 to 90 min from seven normal subjects (group I) and seven patients with chronic renal failure (group II: 4 with normal parathyroid function and 3 with hyperparathyroidism). The resultant time series of serum intact PTH and ionized calcium were assessed by computerized cluster data analysis program. Evaluation of episodic intact PTH pulsatile nature revealed that in group I, 3 out of 7 normal subjects presented 1 maximum and 6 subjects presented at least one minimum. In group II, 3 out of 4 CRF patients with normal parathyroid function presented at least 1 maximum and all four patients at least one minimum. One out of 3 CRF patients with hyperparathyroidism presented 2 maximum and all three at least one minimum. Despite pulsatile character intact PTH levels were maintained all the time within the normal range in control group and in CRF patients with normal parathyroid function. In CRF patients with hyperparathyroidism intact PTH changes were restricted within a level of hyperparathyroidism. Ionized calcium levels in control group remained virtually constant along the period and in CRF group fluctuated widely. Parathyroid hormone is secreted in a pulsatile fashion in normal subjects and in patients with chronic renal failure. One single determination of predialysis intact PTH is a correct method to evaluate parathyroid function since variations due to pulsatile secretion are small.