Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “parathyroid hormone”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,783 records · Page 99Linked to original sources
PubMed1987

Effect of parathyroid hormone on transport by toad and turtle bladder.

We recently demonstrated that parathyroid hormone (PTH) inhibited both vasopressin- and cyclic AMP-stimulated water transport in the toad bladder. This was associated with an increase in calcium uptake by isolated epithelial cells. We postulated that PTH exerts its action on H2O transport by directly stimulating calcium uptake. The current study was designed to compare the effects of PTH and the calcium ionophore, A23187, on H2O and Na transport and H+ secretion in toad and turtle bladders. In toad bladder, PTH and A23187 decreased arginine vasopressin (AVP)-stimulated H2O flow and short-circuit current (SCC) after 60 min serosal incubation. In turtle bladder A23187 decreased SCC to 79.3 +/- 3.6% of base line (P less than 0.05), and significantly decreased RSCC as well. PTH had no effect on SCC or H+ secretion in turtle bladders. Both PTH and A23187 increased 45Ca uptake in toad bladder epithelial cells; only A23187 increased 45Ca uptake in the turtle bladder. The different action of PTH in these two membranes, compared with that of the calcium ionophore, illustrates the selectivity of PTH on membrane transport. PTH increases calcium uptake and decreases transport only in a hormone-sensitive epithelium, whereas the ionophore works in virtually all living membranes. The mode of action of these two agents to increase calcium uptake is, therefore, likely different.

Animals↗
PubMed1989

Circulating molecular forms of parathyroid hormone in primary and secondary hyperparathyroidism.

To study the circulating forms of parathyroid hormone (PTH), sera from 5 patients with primary hyperparathyroidism (PHP) and 12 patients with secondary hyperparathyroidism due to chronic renal failure (SHP) were submitted to gel filtration chromatography. The eluent samples were analyzed using two sequence-specific radioimmunoassays (RIA), one amino-terminal (NH2), the other carboxyl-terminal (COOH). The results obtained with the NH2 RIA showed a single molecular form in both groups co-eluting with the intact hormone. The COOH assay identified several molecular forms with a broader distribution in the SHP patients. These results confirm the diagnostic superiority of the NH2 assay under both conditions.

Chromatography, Gel↗
PubMed2000

Recent studies on the biological action of parathyroid hormone (PTH)-related peptide (PTHrP) and PTH/PTHrP receptor in cartilage and bone.

Mice with a targeted deletion of parathyroid hormone (PTH)-related peptide (PTHrP) develop a form of dyschondroplasia resulting from diminished proliferation and premature maturation of chondrocytes. Abnormal, heterogeneous populations of chondrocytes at different stages of differentiation were seen in the hypertrophic zone of the mutant growth plate. Although the homozygous null animals die within several hours of birth, mice heterozygous for PTHrP gene deletion reach adulthood, at which time they show evidence of osteopenia. Therefore, PTHrP appears to modulate cell proliferation and differentiation in both the pre and post natal period. PTH/PTHrP receptor expression in the mouse is controlled by two promoters. We recently found that, while the downstream promoter controls PTH/PTHrP receptor gene expression in bone and cartilage, it is differentially regulated in the two tissues. 1alpha,25-dihydroxyvitamin D3 downregulated the activity of the downstream promoter in osteoblasts, but not in chondrocytes, both in vivo and in vitro. Most of the biological activity of PTHrP is thought to be mediated by binding of its amino terminus to the PTH/PTHrP receptor. However, recent evidence suggests that amino acids 87-107, outside of the amino terminal binding domain, act as a nucleolar targeting signal. Chondrocytic cell line, CFK2, transfected with wild-type PTHrP cDNA showed PTHrP in the nucleoli as well as in the secretory pathway. Therefore, PTHrP appears to act as a bifunctional modulator of both chondrocyte proliferation and differentiation, through signal transduction linked to the PTH/PTHrP receptor and by its direct action in the nucleolus.

Animals↗
PubMed1992

Parathyroid hormone degradation by opossum kidney cells via receptor-mediated endocytosis and lysosomal hydrolysis.

The mechanisms involved in parathyroid hormone (PTH) degradation by proximal renal tubule cells were studied using an opossum kidney cell line possessing PTH receptors as an in vitro model system. One hour incubation of 5 nmol/l human (h) PTH-(1-84) with intact opossum kidney cells (4.0 x 10(6) cells) resulted in about 70% degradation and disappearance of hPTH-(1-84) from the medium, as determined by a two-site immunoradiometric assay. Preincubation with 100 nmol/l h[Nle8, Nle18, Tyr34]PTH-(1-34)amide for 6, 24, 48 and 72 h caused a 26, 47, 62 and 73% decrease, respectively, in PTH degradation by opossum kidney cells. Binding studies with 125I-labeled h[Nle8,Nle18,Tyr34]PTH-(1-34)amide as a radioligand showed that PTH receptor binding decreased with the time of pretreatment with the agonist. Pretreatments of the cells with monensin, an inhibitor of endocytosis, and the lysosomotropic agents such as chloroquine, ammonium chloride and leupeptin, inhibited degradation of hPTH-(1-84) by 87, 71, 76 and 72%, respectively. Concentrations of 5 nmol/l hPTH-(39-84) and hPTH-(39-68), which are known not to bind to PTH receptors appreciably, were not degraded by opossum kidney cells during 1 h incubations. Thus intact, biologically active PTH, but not its inactive fragments, is degraded by opossum kidney cells, by receptor-mediated endocytosis and lysosomal hydrolysis. A mechanism resembling the peritubular uptake of intact PTH by perfused kidneys reported previously appears to play a main role in PTH metabolism by cultured renal cells.

Animals↗
PubMed2005

Sequential changes in plasma intact and whole parathyroid hormone levels during parathyroidectomy for secondary hyperparathyroidism.

Most commercial assays for intact parathyroid hormone (iPTH) cross-react with non-PTH1-84 fragments (likely to be PTH7-84). We aimed to evaluate a whole PTH assay that measured only PTH1-84 by comparing it with an assay measuring iPTH levels during parathyroidectomy in secondary hyperparathyroidism (HPT). Twenty-eight patients with secondary HPT who underwent total parathyroidectomy with autotransplantation served as subjects. Blood samples for postoperative assay were drawn after anesthesia; immediately prior to excision of the last parathyroid gland; and at 5, 10, and 15 minutes after excision. The PTH7-84 level was calculated by subtracting the whole PTH value from the iPTH value. Plasma whole PTH decreased more rapidly than iPTH after parathyroidectomy (p < 0.0001). PTH levels that decreased by 50% or more from levels prior to excision to 10 minutes after excision were used to predict successful parathyroidectomy; decreases in whole PTH substantiated curative surgery for all patients without introducing false-positive and false-negative results. iPTH levels decreased by at least 50% in only 16 patients at 10 minutes after excision without false-positive results. Out of 11 cases in which iPTH decreased less than 50%, two were true-negatives and nine were false-negatives. Decreases in whole PTH levels more accurately reflect surgical outcome than do decreases in iPTH levels during parathyroidectomy in secondary HPT patients. Even though the quick iPTH assay is used infrequently during surgery for secondary HPT, our results suggest that a quick whole PTH assay may be more useful than the iPTH assay currently used in parathyroidectomy procedures for secondary HPT.

Female↗
PubMed2004

Suppression of parathyroid hormone secretion in CAPD patients by intraperitoneal administration of Maxacalcitol.

BACKGROUND: Maxacalcitol (22-oxacalcitriol; OCT) is a novel vitamin D analogue. In previous clinical studies, OCT was administered three times a week to hemodialysis patients with refractory secondary hyperparathyroidism (2HPT), in whom it acted by inhibiting parathyroid hormone secretion, as well as causing mildly elevated serum calcium. However, intravenous injection of OCT, which requires frequent visits to the outpatient clinic, degrades the quality of life of patients with continuous ambulatory peritoneal dialysis (CAPD) who otherwise visit the clinic only once or twice per month. In the present study, we investigated whether transperitoneal absorption of OCT inhibited intact parathyroid hormone (i-PTH) in CAPD patients when the OCT was added to the peritoneal dialysis fluid. METHODS: Peritoneal dialysis fluid containing 20 micro g of OCT was injected into the peritoneal cavity of five CAPD patients. The serum and peritoneal fluid levels of OCT, i-PTH, calcium, and phosphate were measured before and after treatment. RESULTS: The mean concentration of OCT in peritoneal dialysis fluid rapidly decreased, from 25268.0 pg/ml at 0 h to 1694.0 pg/ml at 2 h and 44.9 pg/ml at 4 h. In contrast, the mean serum OCT level increased from the pretreatment level, which was below the detection limit of the assay, to 656.0 pg/ml at 0.5 h and a peak of 759.0 pg/ml at 1 h, and thereafter gradually decreased, to 713.8 pg/ml at 2 h and 555.8 pg/ml at 4 h. Mean i-PTH significantly decreased, to 83.9% of the baseline level, at 1 h (P < 0.05) and thereafter stayed at around 90%. No consistent trends in calcium and phosphate levels were observed in the five patients. CONCLUSIONS: By injecting OCT into the peritoneal cavity, i-PTH levels could be significantly decreased. These findings indicate the therapeutic efficacy of intraperitoneal administration of OCT for CAPD patients.

Adult↗
PubMed2001

Vitamin D status affects serum parathyroid hormone concentrations during winter in female adolescents: associations with forearm bone mineral density.

BACKGROUND: Vitamin D deficiency leads to secondary hyperparathyroidism, which has a negative effect on bone metabolism in the elderly. Puberty is an important time of bone metabolism and growth. The effect of serum 25-hydroxyvitamin D [25(OH)D] concentrations on parathyroid hormone concentrations and bone mineral density (BMD) has not been well studied cross-sectionally in adolescents. OBJECTIVE: We studied the effect of vitamin D status on serum intact parathyroid hormone (iPTH) concentrations and bone metabolism in adolescents. DESIGN: One hundred seventy-eight healthy female adolescents (aged 14-16 y) volunteered for this study, which was conducted in Finland (Helsinki, 60 degrees N) during the winter. Forearm BMD at radial and ulnar sites was measured by dual energy X-ray absorptiometry. The determinants of different variables were studied by use of regression models. RESULTS: On the basis of the relation between serum 25(OH)D and iPTH concentrations, serum 25(OH)D concentrations > approximately 40 nmol/L were needed to keep serum iPTH concentrations low. One hundred ten subjects (61.8%) had serum 25(OH)D concentrations < or =40 nmol/L. Twenty-four subjects (13.5%) were considered vitamin D deficient when the serum 25(OH)D concentration of 25 nmol/L was used as a cutoff. Subjects with serum 25(OH)D concentrations < or =40 nmol/L had low mean forearm BMD values at both the radial (P = 0.04) and ulnar (P = 0.08) sites. CONCLUSION: A large percentage of adolescent females have low vitamin D status during the winter in Finland, which seems to have negative effects on bone health.

Absorptiometry, Photon↗
PubMed2003

Intraoperative parathyroid hormone assay: an accurate predictor of symptomatic hypocalcemia following thyroidectomy.

HYPOTHESIS: Intraoperative parathyroid hormone (IOPTH) assay is useful for predicting symptomatic hypocalcemia following total thyroidectomy. DESIGN: A prospective study of 30 patients undergoing total thyroidectomy with IOPTH levels obtained following skin closure and ionized calcium (Ca2+) levels obtained 6 hours postoperatively and on postoperative day 1. All patients were evaluated for symptoms of hypocalcemia. SETTING: University teaching hospital. MAIN OUTCOME MEASURES: Patients who developed symptomatic hypocalcemia were compared with asymptomatic patients in regard to age, diagnosis, thyroid weight, thyrotropin level, Ca2+ level, parathyroid status, and IOPTH level. RESULTS: The onset of symptomatic hypocalcemia ranged from 8 to 48 hours postoperatively (n = 10). One patient required readmission. Of 10 patients with symptoms, 5 developed tetany. There were no significant differences in age, diagnosis, thyroid weight, thyrotropin level, or the number of parathyroid glands preserved in patients with or without symptomatic hypocalcemia. All patients with an IOPTH level of less than 10 pg/mL (1.1 pmol/L) had symptoms (n = 8). The mean +/- SD IOPTH level (7.6 +/- 12.0 pg/mL [0.8 +/- 1.3 pmol/L]) in patients who developed symptomatic hypocalcemia was significantly lower than the mean IOPTH level (55.7 +/- 31.8 pg/mL [5.9 +/- 3.3 pmol/L]) in patients without symptoms (P =.001). The 6-hour and postoperative day 1 Ca2+ levels were significantly lower in patients with symptomatic hypocalcemia (P =.19 and P =.13, respectively). An IOPTH level of less than 10 pg/mL is 80% sensitive and 100% specific for the development of symptomatic hypocalcemia. CONCLUSION: The incorporation of the IOPTH assay in the management of thyroid disease is recommended to prevent and prospectively treat symptomatic hypocalcemia, thereby reducing readmissions following thyroidectomy.

Adult↗
PubMed1981

Sex differences during the development of vitamin D deficiency in the rat: serum parathyroid hormone, calcitonin, calcium, and phosphorus.

Male and female Holtzman rats were raised from weaning on a vitamin D-deficient diet (-D). Control (+D) animals were raised on the same diet and orally given 70 IU vitamin D3 twice each week. Serum Ca levels fell at the same rate in -D males and females. In contrast, serum parathyroid hormone increased more rapidly in males than females, but reached the same maximal level in both sexes. There were no sex differences in serum Ca or parathyroid hormone in the +D group. Serum calcitonin increased with age in all groups. This increase began at an earlier age in females than in males in both +D and -D animals. In both sexes, the increase occurred several weeks earlier in +D than in -D animals, and within each of these groups, males had higher phosphate levels than females. Female rats exhibited greater longevity on the -D diet than their male counterparts. Results of this study document prominent sex differences in the endocrine regulation of Ca homeostasis that were revealed during the development of vitamin D deficiency in the rat.

Aging↗
PubMed1977

States of activation of chick kidney adenylate cyclase induced by parathyroid hormone and guanyl nucleotides.

Several aspects of the activation of adenylate cyclase by guanosine 5'-triphosphate (GTP), 5'-guanylylimidodiphosphate (Gpp(NH)p) and bovine parathyroid hormone (bPTH) have been studied in chick kidney plasma membrane preparations. GTP (10(-4) mol/l), Gpp(NH)p (10(-4) mol/l) and bPTH (10 i.u./ml) activated adenylate cyclase without any significant time lag. However a 2 min delay was observed before the activity of the enzyme increased after the addition of bPTH (-6 leads to +34) to incubations. The early (0-3 min) effects of GTP and Gpp(NH)p upon chick kidney adenylate cyclase activity were antagonized by the addition of the alternative guanyl nucleotide. After 5 min of incubation with kidney plasma membranes, Gpp(NH)p induced a stable state of activation of adenylate cyclase which was not reversible by subsequent addition of GTP. GTP did not induce an irreversible state of enzyme activation. In pre-incubation studies, GTP did not produce a persistent enzyme activation and did not modify the effect of Gpp(NH)p added subsequently at the incubation stage. Gpp(NH)p produced a stable state of activation of adenylate cyclase which was not inhibited by addition of GTP at the incubation stage. Bovine PTH (2-34) inhibited the effect of bPTH upon adenylate cyclase activity when the native hormone (10 i.u./ml) had been incubated with plasma membranes for up to 8 min before addition of the analogue (5 mug/ml). Incubation of plasma membranes with bPTH (2-34) for as little as 10 s prevented activation of adenylate cyclase by subsequent addition of bPTH. This pattern was confirmed in pre-incubation studies. After pre-incubation of kidney membranes with bPTH and bPTH (2-34), followed by washing, an acid extract of the membranes contained immunoreactive bPTH. Gpp(NH)p produced a greater increase in adenylate cyclase activity in membranes pre-incubated with bPTH or bPTH (2-34) than in membranes pre-incubated with buffer alone, suggesting that the hormone and analogue facilitated the interaction of Gpp(NH)p with adenylate cyclase.

Adenylyl Cyclases↗
PubMed1977

[Mechanism of action of parathyroid hormone on the functional activity of myocardial tissue].

The effect of the parathyroid hormone (PTH) on AP and the ventricle myocardium contractions in frogs was studied under conditions of the calcium permeability blockade and in calciumfree solution: the AP duration shortened, while AP amplitude increased like in control solution. The hormone's ion mechanisms are supposed to be based on increased transfer of calcium along the "slow" channels of membrane and of sodium--along the "fast" channels, as well as on activation of the Na-K-dependent ATPhase.

Action Potentials↗
PubMed1975

Peripheral metabolism of bovine parathyroid hormone in the dog.

Four dogs were infused with highly purified bovine parathyroid hormone until constant levels of immunoreactive hormone were attained in the circulation. Simultaneous samples of plasma were then obtained from the aorta, from hepatic, renal, and femoral veins, and later from a pulmonary artery and the left ventricle. Radioimmunoassay of these samples revealed mean arteriovenous differences of -23% across the liver and -19% across the kidney. No significant differences were found across the lung or lower extremity. After termination of the infusion the disappearance rate of immunoreactive hormone in external jugular-venous blood was multiexponential: the predominant initial T 1/2 was 4, 6, and 8 min, and the terminal component was 60, 54, and 99 min. respectively, in 3 dogs.

Animals↗
PubMed2000

Complementary nature of radiotracer parathyroid imaging and intraoperative parathyroid hormone assays in the surgical management of primary hyperparathyroid disease: case report and review.

PURPOSE: This article illustrates the complementary nature of preoperative radionuclide parathyroid imaging and intraoperative rapid parathyroid hormone (PTH) assays in primary hyperparathyroid disease. The authors review the literature on these procedures and compare this protocol and its cost-effectiveness with those of the classic four-gland exploration. MATERIALS AND METHODS: Preoperative parathyroid imaging with Tc-99m MIBI and intraoperative rapid PTH assays were performed at the time of neck exploration. RESULTS: One of two parathyroid adenomas seen on radionuclide images would have been missed if the authors had relied solely on the initial decrease in PTH assay value to a normal level. CONCLUSIONS: Tc-99m MIBI imaging and intraoperative rapid PTH assays are complementary; when used together, they lessen the likelihood that abnormal parathyroid glands will be overlooked. This experience and that of others suggest these combined procedures are cost-effective.

Adenoma↗
PubMed1978

Effect of somatostatin on parathyroid hormone and calcitonin secretion.

This study evaluated the effect of somatostatin on immunoreactive parathyroid hormone (iPTH) and calcitonin (iCT) secretion in vivo in rats and monkeys and on iPTH secretion in vitro by normal bovine parathyroid tissue and by a human parathyroid adenoma. Somatostatin infusion promptly (within 0.5 h) suppressed both iPTH and iCT in both species studied in vivo, the suppression being progressive during the infusion period. In in vitro studies, somatostatin caused significant dose-related decreases in basal, low Ca-stimulated, and high Ca-suppressed PTH secretion from normal bovine parathyroid tissue and from basal and low Ca-stimulated PTH secretion from a human parathyroid adenoma. Therefore, somatostatin 1) suppresses both PTH and CT secretion in vivo; 2) acts directly on the parathyroid cell and presumably directly on the C-cell also; 3) acts upon normal and adenomatous parathyroid tissue; 4) suppresses basal, low Ca-stimulated and high Ca-suppressed PTH secretion; and 5) has a dose-related effect. The possible role of somatostatin in the physiological control of PTH and CT secretion (and therefore in Ca homeostasis), and in the pathogenesis of abnormalities of Ca homeostasis, requires further evaluation.

Animals↗
PubMed1984

Sodium gradient-dependent calcium uptake in renal basolateral membrane vesicles. Effect of parathyroid hormone.

The Na+/Ca2+ exchange system in rat renal cortex basolateral membrane vesicles was studied. Uptake and efflux of Ca2+ in the membrane vesicles were stimulated by trans-Na+. The enhancement of Ca2+ uptake by the intravesicular greater than extravesicular Na+ gradient was inhibited by ionophores that dissipated the gradient, and was increased by an outside negative membrane potential. Na+-dependent Ca2+ uptake was saturable with respect to both Ca2+ and Na+. A [Ca2+]0.5 of 8 microM was calculated. The relationship between Na+ concentration and rate of Ca2+ efflux was sigmoidal; a [Na+]0.5 of 15 mM and a Hill coefficient of 2.5 were estimated. Removal of parathyroid glands from the rats resulted in a 40% decrease in the Na+-dependent Ca2+ uptake. Infusion of parathyroid hormone (the synthetic tetratriacontapeptide) into these animals fully restored the activity. The isolated basolateral membrane possessed parathyroid hormone-sensitive adenylate cyclase. These findings may suggest a mechanism by which parathyroid hormone regulates the reabsorption of Ca2+ in the kidney.

Adenylyl Cyclases↗
PubMed1977

Effects of calcitonin and parathyroid hormone on the metabolism of chondrocytes in culture.

Rabbit articular chondrocytes in suspension culture synthesize Type II collagen [3alpha1(II)] in the absence of extracellular Ca2+ and Type I collagen [2alpha1(I) - alpha2] in the complete medium. As a result of pre-treatment in monolayer culture with calcitonin or parathyroid hormone in the complete medium, an influx of Ca2+ into the cells occurs. These cells produce mainly Type I collagen when transferred to suspension cultures in the medium devoid of CaCl2. If added directly to the suspension culture medium containing no CaCl2, calcitonin stimulates an active efflux of Ca2+ from the cells into the medium and leads the cells to synthesize Type I collagen. Under similar conditions, parathyroid hormone does not change the collagen-phenotype.

Animals↗
PubMed1986

Parathyroid hormone: before and after parathyroidectomy.

The clinical value of measuring serum immunoreactive parathyroid hormone (iPTH) for the diagnosis of primary hyperparathyroidism is sometimes debated, and the clinical significance of an elevated postoperative serum iPTH level is unknown. Therefore we studied 141 consecutive patients with primary hyperparathyroidism before and after parathyroidectomy to determine the clinical value of measuring serum iPTH by a mid-region-specific radioimmunoassay. Eighty-eight percent of the patients with primary hyperparathyroidism had an absolute increase in the level of serum iPTH (greater than 40 microliter Eq/ml) before surgery, and the remaining patients had an inappropriately increased level of serum iPTH for the simultaneous serum calcium level. Preoperative serum iPTH level correlated positively with serum calcium level and parathyroid tumor size. Postoperative elevation of serum iPTH level was common (as high as 40%) and was associated with higher preoperative levels of blood urea nitrogen, serum creatinine, and alkaline phosphatase and larger tumors. An elevated postoperative serum iPTH level without hypercalcemia did not indicate a failed parathyroidectomy, whereas negative parathyroid exploration and postoperative hypercalcemia were the best predictors of persistent hyperparathyroidism. We conclude that preoperative serum iPTH measurement is a very sensitive diagnostic test for primary hyperparathyroidism, but postoperative serum iPTH measurement is not a good predictor for persistent or recurrent hyperparathyroidism.

Adult↗