Comparison of the feedback effect of magnesium and calcium on parathyroid hormone secretion in man

ABSTRACT Administration of high doses of magnesium is known to produce a decrease in parathyroid hormone (PTH) secretion in human patients but the effect of magnesium on the secretion of PTH in healthy man is not known. We have looked at the effect of a relatively moderate i.v. dose of magnesium (7·08 mmol) in seven healthy men. In addition and for comparison the effect of calcium (4·25 mmol) was studied. Two magnesium salts were considered, magnesium sulphate (MgSO4) and magnesium pyrrolidone carboxylate (MgPC). Four i.v. injections were given at 08.00 h (MgPC, NaCl (control), MgSO4 and Ca gluconate), with an interval of 1 week between each injection. Whatever the magnesium salt the variations in plasma concentrations of magnesium were the same whereas no change in erythrocyte magnesium was observed. Plasma concentration of C-terminal PTH did not show significant variations after MgPC or saline injection. Both MgSO4 and Ca gluconate produced a statistically significant 30% decrease in plasma PTH levels 45 min after the injection. The effect was more sustained with calcium (2 h) than with magnesium (45 min). The urinary excretion of magnesium was significantly higher after injection of MgSO4 than after MgPC. These results suggest (1) that magnesium was, on a molar basis, less potent than calcium in regulating PTH secretion in vivo, (2) that the nature of the magnesium salt used must be kept in mind for the interpretation of the effect of magnesium on PTH secretion in vivo and (3) that the decrease in plasma PTH can partly explain the larger urinary excretion of magnesium after MgSO4 than after MgPC. J. Endocr. (1987) 113, 117–122

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Differential effects of passive immunization with somatostatin antiserum on adenohypophysial hormone secretions in starved rats

Journal of Endocrinology ◽

10.1677/joe.0.1090169 ◽

1986 ◽

Vol 109 (2) ◽

pp. 169-174 ◽

Cited By ~ 15

Author(s):

J. N. Hugues ◽

A. Enjalbert ◽

E. Moyse ◽

C. Shu ◽

M. J. Voirol ◽

...

Keyword(s):

Binding Capacity ◽

Hormone Secretion ◽

Plasma Concentrations ◽

Passive Immunization ◽

Negative Control ◽

Prolactin Secretion ◽

Male Rats ◽

Minimal Effective Dose ◽

Gh Secretion

ABSTRACT The role of somatostatin (SRIF) on adenohypophysial hormone secretion in starved rats was reassessed by passive immunization. Because of the absence of pulsatile GH secretion in starved rats, the effects of the injection of SRIF antiserum on GH levels can be clearly demonstrated. To determine whether starvation modifies the sensitivity of the adenohypophysis to SRIF, we measured 125I-labelled iodo-N-Tyr-SRIF binding. There was no difference in the dissociation constant (Kd) nor in the maximal binding capacity (Bmax) in fed (n = 15) and starved (n = 15) animals (Kd = 0·38 ± 0·09 (s.e.m.) and 0·45 ± 0·09 nmol; Bmax = 204 ± 39 and 205 ± 30 fmol/mg protein respectively). Administration of SRIF antiserum resulted in a dose-dependent increase in plasma concentrations of GH, TSH and prolactin. The minimal effective dose of SRIF antiserum was 50 μl for GH, 100 μl for TSH and 200 μl for prolactin. Our results show that: (1) starvation does not modify adenohypophysial SRIF-binding sites, (2) in starved male rats endogenous SRIF exerts a negative control on prolactin secretion in vivo and (3) sensitivity to endogenous SRIF seems to be different for each hypophysial cell type. J. Endocr. (1986) 109, 169–174

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Effects of thyroparathyroidectomy, parathyroid hormone, and PTHrP on kidneys of ovine fetuses

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1993.264.1.e37 ◽

1993 ◽

Vol 264 (1) ◽

pp. E37-E44 ◽

Cited By ~ 1

Author(s):

R. J. MacIsaac ◽

R. S. Horne ◽

I. W. Caple ◽

T. J. Martin ◽

E. M. Wintour

Keyword(s):

Parathyroid Hormone ◽

Urinary Excretion ◽

Excretion Rate ◽

Plasma Concentrations ◽

Free Water ◽

Total Calcium ◽

Fetal Plasma ◽

Parathyroid Hormone Related Protein ◽

Fetal Urine ◽

Excretion Rates

The fetal parathyroid glands and parathyroid hormone-related protein (PTHrP) have been shown to be important regulators of fetal calcium metabolism through their actions on the placenta and bone. This study examined the effects of fetal thyroparathyroidectomy (with thyroxine replacement) and exogenous infusion of human parathyroid hormone [PTH-(1–34)], PTHrP-(1–34), and PTHrP-(1–141) on the urinary excretion of calcium in chronically cannulated ovine fetuses during the last one-fifth of gestation. Fetal plasma total and ionized calcium concentrations were significantly lower in thyroparathyroidectomized (TxPTx) fetuses when compared with intact fetuses, but there were no significant differences in urinary excretion rates of total calcium. However, TxPTx produced a significant increase in the fractional excretion rate of total calcium and a significant decrease in the excretion of adenosine 3',5'-cyclic monophosphate (cAMP) compared with intact fetuses. Infusions of PTH-(1–34), PTHrP-(1–34), and PTHrP-(1–141) into the jugular vein of TxPTx fetuses (n = 5) at the rate of 1 nmol/h for 2 h, after a 1-nmol loading dose, significantly decreased the excretion rate of total calcium and increased the excretion rate of cAMP in fetal urine. Infusions of all three peptides resulted in significant increases in the concentration of total calcium in fetal plasma but had no effect on the plasma concentrations or urinary excretion rates of phosphate. Infusion of either PTH-(1–34), PTHrP-(1–34), or PTHrP-(1–141) also resulted in an increase in fetal urine osmolality and pH and a decrease in free water clearance in TxPTx fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)

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Prolactin stimulation of parathyroid hormone secretion in bovine parathyroid cells

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1984.247.5.e675 ◽

1984 ◽

Vol 247 (5) ◽

pp. E675-E680 ◽

Cited By ~ 1

Author(s):

L. Magliola ◽

L. R. Forte

Keyword(s):

Parathyroid Hormone ◽

Hormone Secretion ◽

Vitamin D Metabolism ◽

Parathyroid Function ◽

Wide Range ◽

Camp Levels ◽

Bovine Species ◽

Ca Homeostasis

Previous studies have suggested that prolactin (PRL) may affect calcium (Ca) homeostasis by an action on vitamin D metabolism. In this study, the effects of PRL on parathyroid hormone (PTH) secretion were investigated in dispersed bovine parathyroid cells (PTC). PRL (0.013-1.3 microM) caused concentration-dependent increases in PTH secretion. PRL-stimulated PTH release was apparent as early as 1 h and was progressive thereafter for up to 3 h. PRL enhanced PTH release over a wide range of ambient Ca concentrations (0.5-2.0 microM). Ovine and rat PRL were more effective than bovine PRL in stimulating PTH secretion. This effect was apparently specific for PRL because neither ovine nor bovine growth hormone stimulated PTH secretion. PRL-stimulated PTH release was not mediated through the beta-adrenergic or dopaminergic receptor systems of PTC and was not associated with increased adenosine 3',5'-cyclic monophosphate (cAMP) levels. This study demonstrated a direct effect of PRL to stimulate PTH secretion in vitro. Although these data do not provide evidence for an effect of PRL in vivo, we suggest a mechanism by which PRL may influence parathyroid function and Ca homeostasis in the bovine species.

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Diltiazem stimulates parathyroid hormone secretion in vivo whereas felodipine does not

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.76.4.890 ◽

1993 ◽

Vol 76 (4) ◽

pp. 890-894 ◽

Cited By ~ 2

Author(s):

L. Villiger

Keyword(s):

Parathyroid Hormone ◽

Hormone Secretion

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Direct in vivo comparison of calcium-regulated parathyroid hormone secretion in normal volunteers and patients with secondary hyperparathyroidism.

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jcem.76.6.8501155 ◽

1993 ◽

Vol 76 (6) ◽

pp. 1489-1494 ◽

Cited By ~ 2

Author(s):

J A Ramirez ◽

W G Goodman ◽

J Gornbein ◽

C Menezes ◽

L Moulton ◽

...

Keyword(s):

Parathyroid Hormone ◽

Secondary Hyperparathyroidism ◽

Hormone Secretion ◽

Normal Volunteers

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Effects of 1,25- and 24,25-dihydroxycholecalciferol on parathyroid hormone release from human parathyroid cells in vitro

Acta Endocrinologica ◽

10.1530/acta.0.1050354 ◽

1984 ◽

Vol 105 (3) ◽

pp. 354-359 ◽

Cited By ~ 4

Author(s):

Claes Rudberg ◽

Göran Åkerström ◽

Henry Johansson ◽

Sverker Ljunghall ◽

Jan Malmaeus ◽

...

Keyword(s):

Vitamin D ◽

Parathyroid Hormone ◽

Parathyroid Tissue ◽

Vitamin D Metabolites ◽

Hormone Release ◽

High Doses ◽

Parathyroid Hormone Release ◽

Dispersed Cells

Abstract. The effects of 125-dihydroxycholecalciferol (1,25-(OH)2D3) and 24,25-dihydroxycholecalciferol (24,25-(OH)2D3) on parathyroid hormone (PTH) release from human parathyroid cells were investigated using an in vitro system of dispersed cells. The cells were obtained from 7 patients with primary hyperparathyroidism (HPT) and adenoma, 4 patients with primary HPT due to hyperplasia and 2 patients with parathyroid hyperplasia secondary to chronic renal failure. The dispersed cells were incubated in tissue culture medium at low, normal and high external calcium concentrations for 2–16 h. There was a gradual suppression of PTH release (5–55%) when the calcium concentration in the medium was increased from 0.5 to 3.0 mM, thus indicating retained regulation of hormone release. The addition of 1,25-(OH)2D3 in concentrations of 0.1 and 1 ng/ml and of 24,25-(OH)2D3 in concentrations of 1.0 and 10 ng/ml during the incubations did not further affect the amount of PTH released by the cells. The concentrations of the different vitamin D metabolites tested closely correspond to levels observed under normal physiological conditions and during treatment with high doses of vitamin D in vivo. Thus, the findings contradict the idea of any direct short-term regulatory effect of either 1,25-(OH)2D3 or 24,25-(OH)2D3 on the secretion of PTH from hyperfunctioning human parathyroid tissue.

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