Episodic Secretion of Parathyroid Hormone in Postmenopausal Women: Assessment by Deconvolution Analysis and Approximate Entropy

Abstract

In healthy young subjects, parathyroid hormone (PTH) is secreted presumptively in a dual fashion, with low amplitude pulses apparently superimposed on tonic secretion. In contrast, PTH secretion has not been as well characterized in postmenopausal women, and relationships among bone density, estrogen status, and PTH release have not been explored. It is possible that a pulsatile pattern of PTH secretion is important for bone remodeling, since exogenous PTH administered in a pulsatile manner stimulates bone formation. To assess the importance of pulsatile PTH secretion as a determinant of bone mass, we measured PTH in blood sampled every 2 minutes for 6 h in four groups of older women: (1) high bone density receiving estrogen (n ‫؍‬ 6), (2) high bone density not receiving estrogen (n ‫؍‬ 5), (3) low bone density receiving estrogen (n ‫؍‬ 6), and (4) low bone density not receiving estrogen (n ‫؍‬ 8). The plasma PTH release profiles were subjected to deconvolution analysis, which resolves measured hormone concentrations into secretion and clearance components, and to an approximate entropy (ApEn) estimate, which provides an ensemble measure of the serial regularity or orderliness of the release process. In postmenopausal subjects, PTH was secreted in a fashion similar to that observed in young adults, with significant tonic secretion and PTH pulse occurrences averaging every 18 -19 minutes. Pulsatile PTH secretion accounted for approximately 25% of the total secreted PTH. There were no differences in the amplitude or frequency of pulsatile PTH secretory parameters or in ApEn values among the four groups or compared with young controls. We conclude that in postmenopausal women, PTH secretory patterns and temporal organization are similar to those in healthy young subjects and are not altered in states of low bone density or estrogen deficiency. This suggests that abnormalities in orderly pulsatile PTH secretion are unlikely to play a major role in established postmenopausal osteoporosis. (J Bone Miner Res 1997;12:616-623)

Sampling and storage conditions influencing the measurement of parathyroid hormone in blood samples: a systematic review

“…Studies addressing pulsatile variation of PTH are summarised in Supplemental Data Table 9 [68,76,79,[93][94][95][96][97][98][99][100][101][102].…”

Chronic glucocorticoid treatment alters spontaneous pulsatile parathyroid hormone secretory dynamics in human subjects

“…One reason for these contradictory results may be due to the fact that single random measurements do not reflect the overall pattern of PTH secretion in a given subject nor do they give any insight into possible abnormalities in the secretory dynamics of PTH as a consequence of the glucocorticoids. This point is particularly relevant since it is now known that PTH is secreted both in low amplitude pulses and in a tonic secretory state (16,17). Until the results of this study, no comparable data were available on pulsatile vs tonic secretory PTH dynamics in patients chronically treated with glucocorticoids.…”

“…In healthy individuals, pulsatile PTH secretion accounts for approximately 25% of the total secreted PTH (15). No significant differences in these secretory dynamics have been observed between normal men and women (16) nor have there been any significant correlations between these patterns and the ambient PTH or ionized calcium concentration (17). In a disorder such as postmenopausal osteoporosis, however, dampened PTH pulsatility has been reported in some but not all early studies (13,14,17).…”

“…No significant differences in these secretory dynamics have been observed between normal men and women (16) nor have there been any significant correlations between these patterns and the ambient PTH or ionized calcium concentration (17). In a disorder such as postmenopausal osteoporosis, however, dampened PTH pulsatility has been reported in some but not all early studies (13,14,17). Pulsatile (once daily) administration of PTH in low doses can be associated in animals and in human subjects with a preferential stimulation of new bone formation (18 -22).…”

Glucocorticoids and bone: cellular, metabolic and endocrine effects

“…Recent studies have established that in healthy young subjects, PTH secretion has two major components: a predominantly tonic pattern of constant secretion and low amplitude pulses with high frequency (approximately every 15-20 minutes). In healthy individuals, pulsatile PTH secretion accounts for approximately 25% of the total secreted PTH 49,50 . We have recently found that PTH secretory dynamics are altered by glucocorticoids with a reduction in the tonic component and an exaggeration in the pulsatile component of PTH secretion that override normal secretory dynamics 51 .…”