ABSTRACT
In patients with secondary hyperparathyroidism (HPT) caused by chronic renal failure (CRF), the pulsatility of parathyroid hormone (PTH) secretion and the relation of PTH to plasma Ca2+ concentrations were investigated. Intermittent hyper- and hypocalcemia was induced to study the deterministic reaction of the parathyroid glands. Compared to normal behaviour in CRF the pulsatility is lost. Yet the deterministic coupling between PTH and Ca2+ concentrations remains qualitatively the same though quantitatively it is exaggerated and varies depending on the subjects.
Subject(s)
Calcium/blood , Kidney Failure, Chronic/metabolism , Parathyroid Hormone/blood , Adult , Aged , Female , Humans , Hypercalcemia/etiology , Hypercalcemia/metabolism , Hyperparathyroidism/etiology , Hyperparathyroidism/metabolism , Hypocalcemia/etiology , Hypocalcemia/metabolism , Kidney Failure, Chronic/complications , Male , Mathematics , Middle Aged , Parathyroid Hormone/metabolism , Pulsatile Flow/physiologyABSTRACT
In seven normal men we investigated the basal secretion of PTH by blood sampling in 30 sec intervals for estimation of intact PTH and at 2-min intervals for measurement of ionized calcium. In 4 of these subjects we also investigated the PTH-secretion under conditions of intermittent hypercalcemia and hypocalcemia. Our measurements demonstrate the existence of three time scales in the secretion of PTH, viz. short-term pulses (faster than 2 min), an intermediate pattern of adjusting PTH levels to changed Ca2+ averages, and finally a long-term coupling between PTH and Ca2+ averages after 20 min. Ionized calcium controls the long-term regulation and intermediate adaptation mechanisms, but the short-term fluctuations seem to be due to spontaneous secretion.
Subject(s)
Calcium/blood , Parathyroid Hormone/metabolism , Adult , Humans , Male , Parathyroid Hormone/bloodABSTRACT
Although the pathophysiology of postmenopausal osteoporosis has been investigated extensively, it is still not established in what respect PTH is related to the events. Recently, consistent data on the pulsatile secretion of PTH in man have been published. In this study intact PTH was measured in six early postmenopausal women before and after 6 months of hormone replacement therapy (HRT; 0.6 mg conjugated estrogens and 5 mg medrogestone). In addition to parameters of calcium metabolism and bone mass and to control HRT, intact PTH was measured in blood drawn over 6 h every 2 min. With HRT there was a 30% reduction in PTH secretion. Both the amount secreted per pulse (baseline, 26.8 +/- 6.9 ng/L; HRT, 21.4 +/- 7.6 ng/L; P < 0.05) as well as the basal secretion (baseline, 232.6 +/- 117.6 ng/L.h; HRT, 145.5 +/- 80.0 ng/L.h; P < 0.01) were reduced, whereas the pulse count per h remained constant (baseline, 5.1 +/- 2.2; HRT, 5.1 +/- 1.3). Power spectrum analysis showed a shift in spectral maxima consistent with these findings. Ionized and total calcium were slightly, but nonsignificantly, reduced with treatment. In summary we conclude that in early postmenopausal women, HRT reduces the secretion of PTH by reducing both the basal secretion and the amount secreted per pulse. It is conceivable that some of the known effects of HRT on bone metabolism might be mediated by the modulation of PTH secretion.
Subject(s)
Estrogen Replacement Therapy , Parathyroid Hormone/blood , Postmenopause/blood , Calcium/metabolism , Female , Follicle Stimulating Hormone/blood , Humans , Middle Aged , Osmolar Concentration , Osteocalcin/blood , Phosphates/blood , Time FactorsABSTRACT
The biological importance of dynamic hormonal secretion has been demonstrated. There is good evidence from recent studies that parathyroid hormone (PTH) which plays an important role in bone physiology is secreted in a pulsatile manner. In this study we performed a classification of two 'dynamical diseases' namely osteoporosis and hyperparathyroidism by the visualization of dynamic PTH-secretion in multidimensional phase spaces.
