Intact parathyroid hormone in primary hyperparathyroidism

Abstract

In 49 patients with primary hyperparathyroidism, intact parathyroid hormone (PTH) was measured with a recently developed immunoradiometric assay, and midregional PTH fragments (sequence 44-68) were measured with an established radioimmunoassay technique. In 47 normal subjects, the concentration of intact PTH ranged from 2.0 to 6.8 pmol/l, and in 49 patients with primary hyperparathyroidism it ranged from 6.4 to 80.0 pmol/l. In contrast, midregional PTH fragments were normal in seven of 49 patients with primary hyperparathyroidism. In five healthy controls and in 12 patients with surgically confirmed primary hyperparathyroidism and serum calcium levels below 3.0 mmol/l, a rapid calcium loading test was performed. In healthy controls, intact PTH was in the low normal to subnormal range within 2.5-5.0 min, and had recovered within 15 min of calcium infusion. In patients with primary hyperparathyroidism, the calcium infusion also led to a 30-50 per cent decrease in intact PTH levels within 5.0-7.5 min after injection, with a slow recovery after 10-15 min. In six of the patients with only slightly elevated basal intact PTH, a suppression to the normal range was observed. In 24 patients (16 patients with a solitary adenoma and eight patients with four-gland hyperplasia) the intact PTH levels were followed intraoperatively during parathyroidectomy, revealing a significantly different rate of decline for single adenomas compared with hyperplasia during the first 15 min after removal of the primary enlarged gland. Intact PTH values remained constantly elevated in one patient with primary hyperparathyroidism and an unsuccessful neck exploration. These results confirm that (a) the measurement of intact PTH in patients with primary hyperparathyroidism is superior to the measurement of midregional fragments; (b) PTH secretion in primary hyperparathyroidism is not totally autonomous; and (c) intraoperative monitoring of intact PTH values could be used to monitor the success of surgery.

Direct Effect of Acute Metabolic and Respiratory Acidosis on Parathyroid Hormone Secretion in the Dog

“…The disappearance curve for PTH was measured after a parathyroidectomy, which was performed immediately after the induction of hypocalcemia. The short half‐life of iPTH, which we observed in the dog, is in agreement with previous studies performed in humans (49–51) . In our study, the half‐life of PTH was not affected by the presence of Resp Acid.…”

Metabolic Evaluation: Place of the Calcium Load Test: How, When, For Whom, and Why?

“…A PTH-IR cutoff at 73% has been proposed to differentiate normocalcemic early-stage PHPT patients (PTH-IR <73%) from healthy subjects (PTH-IR >73%) with sensitivity of 95% and specificity of 99.9% [13]. These findings are in agreement with earlier studies on the calcium dependency of PTH secretion [7][8][9][10][11]18]. In fact, PHPT is considered as a biphasic disease, whereby PTH rises first, followed by a rise in serum calcium in later stages of the disease [19].…”

“…There are slight variations in CLT study protocols in the literature in terms of the following parameters: content and duration of the low-calcium diet and fasting period; content and route of administration of the calcium load; duration of urine collection; and time points for blood withdrawal [5,[7][8][9][10][11][12][13][14]. The CLT protocol described above together with Figure 1 should be understood as a comprehensive summary from our review of the various protocols and pathophysiological mechanisms presented in all the published studies on CLT in adults to date [5,[7][8][9][10][11][12][13][14]. The impact of CLT protocol variations has not been evaluated in any dedicated study to date.…”

The importance of the unsuppressed glands in the study of intact parathyroid hormone disappearance after parathyroid adenomectomy

“…The fits were generally very good and all the curves were less than 50% of the clamping value at 15 min, except for those for patients C17 and C19, whose values remained over 50% of the clamping value at 30 min; the two curves had a very slow decline because of their normalization to a value which was far lower than the respective BV value. This difference may reflect the preceding devascularization of the adenoma by the operative exploration and manipulation of the enlarged gland, as was previously noted by other authors (14). The last experimental points (not plotted in Fig.…”