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PubMed1991

Measurement of intact parathyroid hormone in the diagnosis of hyperparathyroidism.

Plasma levels of parathyroid hormone were determined pre-operatively in 27 consecutive patients with clinical and biochemical signs of primary hyperparathyroidism, by the use of one assay recognizing the intact PTH molecule and one assay recognizing the mid-portion of PTH. Plasma levels of mid-molecule PTH were normal in 5 of the patients with primary hyperparathyroidism. In 4 of these patients, plasma levels of intact PTH were raised. Conversely, in 6 patients with primary hyperparathyroidism, intact PTH were normal pre-operatively. In 5 of these cases, plasma levels of mid-molecule PTH were raised. The EDTA infusion test was performed in 6 patients with normal baseline plasma level of intact PTH pre-operatively. The test correctly predicted all the patients in this group who were found to have primary hyperparathyroidism, as well as a patient with normal parathyroid glands found at operation. We conclude that some patients with primary hyperparathyroidism have normal baseline plasma levels of intact PTH. In these patients, plasma levels of mid-molecule PTH and an EDTA infusion test provide further diagnostic information.

Adult↗

PubMed2004

Major method-specific differences in the measurement of intact parathyroid hormone: studies in patients with and without chronic renal failure.

BACKGROUND: Following the introduction of two-site immunometric assays for parathyroid hormone (PTH), the expectation of good inter-assay agreement has not been fulfilled. The reasons for this may include differences in standardization as well as fragment recognition between the assays. METHODS: PTH values for healthy individuals, patients with renal failure and patients with normal renal function and elevated parathyroid hormone (hPTH) were compared using two commercial two-site immunochemiluminometric assays (Bayer Magic-lite and DPC Immulite 2000). RESULTS: Immulite results had a mean value 50.4% greater than the corresponding Magic-lite values for the whole study population with individual values ranging from 17.5% below to 118.3% above the corresponding Magic-lite value. There was no significant difference in inter-assay bias between patients with renal failure and those with normal renal function, suggesting that variable cross-reactivity with circulating disease-specific PTH fragments was not the primary cause of the observed discrepancy. Cross-reactivity with the synthetic fragment hPTH (7-84) was 34+/-5% for Magic-lite and 62+/-2% for Immulite. We also studied the stability of synthetic hPTH on storage. CONCLUSION: The instability of synthetic hPTH over extended storage periods may affect primary standard material. The consistent inter-assay differences and the over-recovery observed in external quality assessment programmes for the Immulite assay may have best been explained by differences in calibration and the relative cross-reactivities and/or kinetics of the two assay systems for specific parathyroid fragments.

Humans↗

PubMed2000

Primary hyperparathyroidism with normal serum intact parathyroid hormone levels.

To evaluate the features of primary hyperparathyroidism (HPT) with normal serum intact parathyroid hormone (iPTH) levels, we studied 271 consecutive patients undergoing surgery for primary HPT. In 20 patients, serum iPTH levels were within the normal range (10-65 ng/l). In their records, the most common clinical features were fatigue (n=13), polyuria (n=6), renal stone (n=5), and hypertension (n=5). Mean serum calcium and phosphorus were 2.78 and 0.85 mmol/l, respectively: 14 had serum phosphorus within the normal range. Mean serum iPTH was 48.5 ng/l, and was <45 ng/l in nine patients. Cervical ultrasound demonstrated a parathyroid adenoma in nine, and was normal in four. Tc sestamibi parathyroid scintigraphy always demonstrated an adenoma (9/9). In eight patients, normal iPTH values delayed diagnosis. Physicians should be aware of the possibility of HPT in patients with hypercalcaemia, even when serum phosphorus and iPTH levels are within the normal limits. Particularly, HPT cannot be excluded when serum iPTH levels are below the upper part of the normal range. In such cases, cervical imaging, which has the same sensitivity as in other HPT, should be undertaken. These explorations are useful, because many patients are symptomatic and can take advantage of surgery.

Adenoma↗

PubMed1986

Placental transfer of parathyroid hormone.

We investigated the in vitro transfer of three parathyroid hormone (PTH) fragments (amino acids 35-84, 44-68 and 65-84) through human placenta at term. The perfused and transferred fragments were measured radioimmunologically and identified by three different methods: high-pressure-liquid chromatography (HPLC), preparative flat-bed electrofocusing (PEGG), and gel filtration (GF). The study demonstrated that PTH fragments traverse the human placenta. The transferred and perfused fragments were identical. We observed a significant degradation of the perfused hormone during the passage through the placenta in both fetal and maternal directions. In addition, we measured the PTH concentrations on forty samples of maternal and umbilical cord artery and vein plasma obtained immediately after delivery. A highly significant correlation of PTH concentrations in the maternal and umbilical cord vessels was observed. These findings support the contention that human placenta at term is permeable for PTH fragments.

Female↗

PubMedDate not supplied

Biological activity of parathyroid hormone antagonists substituted at position 13.

Lysine occupies position 13 in the parathyroid hormone (PTH) antagonist, [Nle8,18,Tyr34]bPTH(7-34)NH2. Acylation of the epsilon-amino group in lysine 13 by a hydrophobic moiety is well tolerated in terms of bioactivity: the analog [Nle8,18, D-Trp12,Lys 13 (epsilon-3-phenylpropanoyl),Tyr34]bPTH(7-34)NH2 is equivalent to the parent peptide in its affinity for PTH receptors and its ability to inhibit PTH-stimulated adenylate cyclase in both kidney- and bone-based assays. Truncation of this peptide by deletion of phenylalanyl7 with concomitant removal of the amino-terminal alpha-amino group yielded the analog desamino[Nle8,18,D-Trp12,Lys13 (epsilon-3-phenylpropanoyl),Tyr34]bPTH(8-34)NH2, an antagonist of high potency in vitro (Kb = 4 and 9 nM, Ki = 73 and 3.5 nM in kidney- and bone-based assays, respectively). Also this analog is potentially stable to aminopeptidases present in many biological systems.

Acylation↗

PubMed1990

Effect of methionine oxidation and deletion of amino-terminal residues on the conformation of parathyroid hormone. Circular dichroism studies.

Circular dichroism (CD) studies of parathyroid hormone (PTH), its oxidized forms, and some fragments of the hormone are described. The CD spectrum of native PTH (84 amino acids) and the active fragment, 1-34 PTH, suggests that most of the secondary structure resides in the amino-terminal segment of this hormone. Oxidation of the methionine residue at position 18 has a small impact on secondary structure, whereas oxidation of the methionine at position 8 produces substantial changes. Oxidation of both methionines produces secondary structure changes that are greater than the sum of those seen upon oxidation of the individual methionines. The CD spectrum for the 3-34 fragment of PTH is identical to that of the 1-34 fragment, and that of the 7-34 fragment is only slightly different. The spectra of the 13-34 and 19-34 fragments are markedly altered from that of the 1-34 peptide, and those of the 9-84 and 19-84 fragments of native PTH are significantly different from the intact hormone. Computer-assisted estimates of secondary structure content, and difference spectra, were utilized to evaluate the secondary structure content of the peptides. These results suggest that residues 6-12 are important in formation of helical secondary structure and that a reverse turn may be important for the folding of PTH into a conformation with high affinity for receptors. Residues 1 and 2 appear to make no contribution to the secondary structure and may be directly involved in activation of receptors.

Animals↗

PubMed2000

Pulsatile parathyroid hormone secretion in health and disease.

In humans plasma parathyroid hormone (PTH) fluctuates episodically at a frequency of 6-7 bursts per hour. Approximately 30% of circulating PTH is attributable to pulsatile secretion and 70% to tonic secretion. PTH release is tightly controlled by Ca2+. Acute hypocalcaemia elicits a biphasic wave of PTH release, with an initial selective amplification and acceleration of the pulsatile component followed by proportionate stimulation of pulsatile and tonic secretion. Acute hypercalcaemia submaximally suppresses the frequency and mass of PTH bursts as well as tonic PTH release. Patients with primary hyperparathyroidism exhibit proportionate increases in pulsatile and tonic secretion, with no change in pulse frequency. In secondary hyperparathyroidism due to renal insufficiency, tonic secretion and pulsatile burst mass are also proportionately amplified, and burst frequency is increased. Moreover, the hypocalcaemia-induced increase in burst frequency and mass as well as their suppression during hypercalcaemia is diminished, suggesting partial uncoupling of hyperplastic parathyroids from physiological regulatory mechanisms. While the secretory pattern of PTH and its dysregulation in disease states is now well defined, the functional significance of pulsatile PTH signalling for target tissues is still largely unexplored. Preliminary work indicates that intermittent, in contrast to continuous, PTH administration stimulates bone formation. Cell culture studies suggest PTH receptor down-regulation with tonic exposure.

Bone Diseases↗

PubMed1976

Circulating levels of immunoreactive parathyroid hormone in endemic genu valgum.

Circulating levels of immunoreactive parathyroid hormone (PTH) were estimated in fifteen normal subjects and twenty-five subjects suffering from the skeletal fluorosis, ten of whom had associated endemic genu valgum. Levels of PTH were high in all the subjects with fluorosis as compared to normals, but among fluorosis subjects, those who had endemic genu valgum had values strikingly higher than those without. It is suggested that secondary hyperparathyroidism may have a significant role to play in the pathogenesis of osteoporosis seen in patients with endemic genu valgum.

Adolescent↗

PubMed1987

Effect of age on circulating immunoreactive and bioactive parathyroid hormone levels in women.

Although levels of serum immunoreactive parathyroid hormone (iPTH) increase with age in women, this could be caused by retention of non-biologically active PTH fragments by the aging kidney. In 102 normal women, aged 30 to 89 yr, serum iPTH increased with age by 58% (r = 0.33, p less than 0.001) with antiserum GP-1M (which has midmolecule specificity) and 43% (r = 0.32, p less than 0.001) with antiserum CH-12M (which may have whole molecule specificity); urinary cAMP/GFR excretion increased by 29% (r = 0.22, p less than 0.05). The results of these assays were validated by comparison with serum levels of biologically active PTH (BioPTH) in immunoextracts of serum followed by renal adenylate cyclase assay in a selected subgroup of 25 of the women. Serum BioPTH correlated with serum iPTH assessed by antiserum GP-1M (r = 0.48, p less than 0.05) and antiserum CH-12M (r = 0.48, p less than 0.05) but not with urinary cAMP. The data are consistent with an increase of parathyroid function with aging: clearly, we do not find decreased parathyroid function as would be expected if age-related bone loss was not mediated, in part, by PTH.

Adult↗

PubMed1985

Genes for insulin I and II, parathyroid hormone, and calcitonin are on rat chromosome 1.

Insulin, parathyroid hormone, and calcitonin are polypeptide hormones that regulate important physiological processes in target tissues. Rat genes encoding each hormone were chromosomally assigned to rat chromosome 1. Both rats and mice have two insulin genes (I and II). However, in contrast to mice in which insulin I and II are asyntenic, rat insulin I and II were both localized to chromosome 1. This study identifies a conserved syntenic group on rat chromosome 1, and implies that mouse insulin I and II genes were chromosomally separated after rats and mice diverged 20-35 million years ago.

Animals↗

PubMed1975

Further studies on acetamidination as a technique for preparation of a biologically valid 3-H-labeled tracer for parathyroid hormone.

The technique of acetamidination of amino groups in parathyroid hormone (PTH) for the purpose of preparation of a tritiated, biologically valid tracer for this hormone, has been more extensively studied. It was found that eight of the ten amino groups in PTH are readily reactive but that two appear unreactive. The kinetics of labeling suggest that preparations of PTH which are labeled to this level of 80% of theoretical consist of a homogeneous population of molecules in which each PTH molecule contains eight tritiated acetamidino groups. There is no question of the presence of unlabeled hormone in such preparations. Eighty per cent labeled acetamidino-PTH is identical, qualitatively and quantitatively, in its biological activity with native PTH as shown by three accepted bioassays: serum calcium elevation, urine phosphate excretion, and activation of kidney cortex plasma membrane adenylate cyclase in vitro. The dose-response relationships are identical for labeled and native hormone in all three systems. Tritiated acetamidino-PTH tends to lose biological activity on storage but full activity can be regained by reduction of the hormone with excess cysteine. However, cysteine reduction conducted at 80 degrees for 2 hours causes some loss of tritium from the hormone. Therefore, dithiothreitol reduction at room temperature was utilized to maintain biological activity. Eighty per cent acetamidino-PTH can be further purified by ion exchange chromatography on carboxymethylcellulose using a continuous gradient of sodium acetate in 8 M urea. Such chromatography reveals the presence of isohormones in both cold and radioactive PTH. Co-chromatography of tritiated acetamidino-PTH with a cold isohormone of PTH shows that while the isohormones can be separated from one another, the acetamidino derivatives of each isohormone elute in a virtually identical position with their parent unlabeled PTH molecule.

Adenylyl Cyclases↗

PubMed1992

Parathyroid hormone and calcium behavior in advanced congestive heart failure.

Parathyroid hormone (PTH) regulates the content of calcium and thus exerts an effect on myocardial function. Abnormal secretion of PTH has been sporadically reported to be associated with depressed mechanical performance of the heart muscle. In the present study, we first measured PTH levels at baseline in 27 consecutive patients with advanced congestive heart failure (LVEF: 17 +/- 9%): five patients (18.5%) revealed elevated PTH levels, one case of hypoparathyroidism was discovered. Furthermore, nine unselected patients underwent symptom-limited exercise stress test leading to an increase in mean pulmonary artery pressure from 25.6 +/- 15 at baseline to 41.2 +/- 18 mm Hg at peak exercise. In contrast to observations in healthy subjects, in heart failure patients both mean PTH and blood calcium concentrations did not change significantly during peak exercise or recovery. Moreover, patients with the lowest left-ventricular ejection fraction showed a decrease in PTH during maximal stress. We conclude that abnormal baseline PTH secretion is common in patients with advanced congestive heart failure. More importantly, these studies show that PTH release is depressed under stress conditions, possibly indicating a dysfunction of the parathyroid gland in severe heart failure.

Adult↗

PubMed1992

Evolution of osteocalcin, alkaline phosphatase and parathyroid hormone after parathyroidectomy in patients receiving chronic maintenance hemodialysis.

Parathyroid hormone (PTH), osteocalcin and alkaline phosphatase (AP) were investigated before and after parathyroidectomy in 12 patients receiving hemodialysis. Early post-parathyroidectomy, PTH decreased (p less than 0.001), AP increased (p less than 0.05), but osteocalcin remained unchanged. At 3 months, osteocalcin and AP declined. A negative correlation was observed between aluminum staining and post-parathyroidectomy osteocalcin. In conclusion, early post-parathyroidectomy, osteocalcin and AP reflect persistent osteoblastic activity, which declined after 3 months. In patients receiving hemodialysis both variables may represent different aspects of osteoblastic activity and osteocalcin allows mixed uremic osteodystrophy after parathyroidectomy.

Adult↗

PubMed2000

Serum parathyroid hormone and calcitonin levels in racehorses with fracture.

Serum parathyroid hormone (PTH) and calcitonin (CT) levels in fractured racehorses were measured by radioimmunoassay. Racehorses with fracture of large bone such as the radius, third metacarpus, third carpus, digital bone or tibia, showed normal PTH level and elevated CT level in the serum. Serum PTH level was slightly higher in racehorses with sesamoid bone fracture compared to that of healthy racehorses, but not statistically significant. Moreover, serum CT level of racehorses with sesamoid bone fracture was significantly higher than that of healthy racehorses. Racehorses with sesamoid bone fracture and large bone fracture might be in different conditions of calcium regulation.

Animals↗

PubMed1975

Calcium transport in isolated bone cells. III. Effects of parathyroid hormone and cyclic 3',5'-AMP.

The effects of parathyroid hormone (PTH) and cyclic 3',5'-AMP (cyclic AMP) on calcium transport were studied in isolated bone cells. Bone cells were isolated by collagenase digestion of 20-21 day old fetal rat calvaria. Calcium transport was measured with 45Ca. PTH (0.2 mug/ml) increased calcium uptake 30--40% over control values at 37 C. At 4 C, the effects were magnified and 70--170% increases in calcium uptake were observed. The effects were present 1--10 minutes after the simultaneous addition of hormone and 45Ca. PTH had no effect on calcium efflux. Neither dibutyryl cyclic AMP (10(-4)-10(-3)M) nor cyclic AMP (10(-7)-3 X 10(-6)M) had any effect on calcium uptake or efflux. Methylisobutylxanthine (0.1 mM) caused no change in calcium uptake although increase in cyclic AMP were noted. The characteristic PTH-induced increase in cyclic AMP seen at 37 C was not observed at 4 C. It is postulated that PTH increases the permeability of bone cell membranes to calcium. At 4 C the membrane is relatively impermeable so the PTH effect is magnified. The PTH-induced increase does not appear to be mediated through cyclic AMP.

Animals↗

PubMed1988

Synthetic human parathyroid hormone 1-34 fragment for diagnostic testing.

Since bovine parathyroid extract became unavailable for stimulatory testing, the differentiation between hypoparathyroidism and pseudohypoparathyroidism has been made from the measurement of serum parathyroid hormone (PTH) values alone. Responsiveness to PTH can once again be tested with teriparatide acetate, the newly available, biologically active 1-34 fragment of human PTH. The PTH infusion test can be used to confirm a preliminary diagnosis based on serum immunoreactive PTH values, to differentiate between type 1 and type 2 pseudohypoparathyroidism, or to detect a subtle abnormality of calcium metabolism in normocalcemic patients with features suggesting pseudohypoparathyroidism. Of several variables used to express changes in renal metabolism of cyclic adenosine 3',5'-monophosphate (cAMP) or phosphate, the 30-minute change in cAMP excretion per unit of glomerular filtration and the 60-minute percentage fall in the tubular maximum for phosphate reabsorption provide the best discrimination. Teriparatide has a low incidence of adverse reactions and provides an effective diagnostic tool.

Costs and Cost Analysis↗

PubMed1983

Relaxation of bovine, porcine and human brain arteries by parathyroid hormone.

We have studied the relaxant effect of bovine parathyroid hormone (bPTH) on helical strips of branches of bovine and human middle cerebral arteries and bovine and porcine basilar arteries. All arteries were studied after contraction with prostaglandin (PG) F2 alpha or KCl. In the case of all arteries contracted with PGF2 alpha, the ED50 of PTH vasorelaxation related to maximal vasorelaxation induced by papaverine ranged from 9 to 14 nM for bPTH-(1-34) and 100 to 220 ng/ml for native bPTH-(1-84). The PTH inhibitor, [Nle8, Nle18, Tyr34]bPTH-(3-34) amide, attenuated the vasorelaxant effect of both bPTH-(1-34) and bPTH-(1-84). The vasorelaxant effects of PTH which we have observed in this study are consistent with the stimulatory effects of PTH on vascular adenylate cyclase which we had previously reported.

Adult↗

PubMed1992

Characterization of two novel polymorphisms at the human parathyroid hormone gene locus.

Two new polymorphisms within the human parathyroid hormone (PTH) gene are described. One corresponds to a C----A transversion that destroys DraII and NlaIV restriction sites. The other is revealed by the enzyme XmnI, and its position has been mapped with respect to the PTH gene. We have also identified a sequence change that results in the TaqI restriction fragment length polymorphism (RFLP) described previously at this locus and have found that this sequence change also results in disruption of a BstBI site. Finally, we describe a polymerase chain reaction (PCR)-based method that permits a rapid evaluation of the DraII and BstBI (TaqI) polymorphisms. The introduction of these two additional RFLPs and this PCR-based assay should considerably extend the power of genetic analyses of the human PTH gene.

Base Sequence↗