Significance of early increase in stable and radioactive plasma calcium after parathyroidectomy in primary hyperparathyroidism

Reduction of serum parathyroid hormone levels during sympathetic stimulation in man

The parathyroid glands contain sympathetic nerve endings and the parathyroid cells are endowed with beta-adrenergic receptors. The physiological role of the sympathoadrenal system for the secretion of parathyroid hormone (PTH) has, however, not been clarified. Using the technique of lower body negative pressure (LBNP), which is an established method to achieve sympathetic nerve activation, it was found in 17 healthy subjects that the venous serum levels of PTH were reduced by 7% within 20 min [from 0.79 +/- 0.12 (SD) to 0.74 +/- 0.11 arbU/l, p less than 0.01, paired t test]. The reduction corresponds to 30% of the maximal suppressibility of PTH by induced hypercalcemia or following parathyroidectomy when studied with the same PTH assay and with the short time period involved. After cessation of LBNP the PTH levels returned to baseline within 20 min. There were no concomitant changes of the plasma ionized calcium concentrations. The findings are compatible with a role for the sympathetic nervous system in the physiologic regulation of the secretion of PTH.

Clinical significance of free plasma hydroxyproline measurement in metabolic bone disease

Free hydroxyproline was measured in plasma of 67 normal subjects and in 70 patients with bone disease including primary hyperparathyroidism (n = 19), osteoporosis (n = 18), Paget's disease (n = 14), cancer involving bone (n = 8), chronic renal failure (n = 6), and osteomalacia (n = 6), and osteomalacia (n = 5). A good correlation was found between plasma and urinary values of the amino acid in normal subjects (r = 0.66; p less than 0.001). In patients with skeletal disorders a highly significant direct correlation was observed between free plasma hydroxyproline on the one hand and urinary hydroxyproline (r = 0.92; p less than 0.001) and serum alkaline phosphatase activity (r = 0.86; p less than 0.001) on the other, even though there were a few examples of dissociations among these parameters. Free plasma hydroxyproline decreased in the patients with Paget's disease following chronic administration of salmon calcitonin. Following successful parathyroidectomy, free plasma levels of hydroxyproline decreased in all the cases studied. Measurement of free plasma hydroxyproline thus appears to provide a specific index of bone metabolism that may be usefully employed as an alternative to the assay of other markers of bone turnover.

Acute effects of removal of parathyroid adenoma on plasma and urinary hydroxyproline levels

This study was carried out to investigate early effects of parathyroidectomy (PTx) on bone matrix collagen metabolism. Eleven patients suffering from primary hyperparathyroidism were studied by measuring urinary excretion of hydroxyproline (OHPr) and cAMP in samples collected before PTx and, on the day of surgery, at intervals of 1-3 h for the first 10 h and then at longer intervals. In six patients nondialyzable urinary OHPr and free plasma aminoacid levels were also assayed. We found that the average period required for OHPr/Cr ratio and plasma OHPr to reach normal values was longer than the mean time required for cAMP/Cr ratio to reach normal limits. In all patients the total amount of nondialyzable OHPr decreased in the first 24 h after PTx but thereafter a daily increase in the urinary excretion of nondialyzable component was seen, so that the fractional amount of nondialyzable OHPr in the fourth postoperative day (26.8 +/- 5.2 SE) was significantly higher than that of preoperative one (6.1 +/- 1.0; p less than 0.02). Our results confirm that PTx induces a reduction in the rate of bone collagen resorption and indicate that changes of OHPr/Cr ratio and free plasma OHPr values may be considered useful indices of successful parathyroid surgery, even though they lag behind those of cAMP. The different behavior of total and nondialyzable OHPr after surgery indicates that acute deficiency of parathyroid hormone induces a positive uncoupling of the two processes of bone remodeling, thus supporting the view that the acute direct effect of the hormone on bone formation is an inhibition of this process.