Preoperative Calcium and Parathyroid Hormone Values Are Poor Predictors of Gland Volume and Multigland Disease in Primary Hyperparathyroidism: A Review of 2000 Consecutive Patients

ObjectiveCalcium and parathyroid hormone (PTH) values are believed to have a linear relationship in patients with primary hyperparathyroidism and correlate with parathyroid gland size, with higher values predicting single-gland disease. In this modern series, these preoperative values were correlated with operative findings to determine their utility in predicting the gland involvement at parathyroid exploration.MethodsTwo thousand consecutive patients who underwent initial surgery for sporadic primary hyperparathyroidism from 2000 to 2014 were reviewed. All patients underwent a 4-gland exploration. Relationships between preoperative calcium and PTH values with the total gland volume of each patient were examined and stratified using the number of involved glands: single adenoma (SA), double adenoma (DA), and hyperplasia (H).ResultsThere were 1274 (64%) SA, 359 (18%) DA, and 367 (18%) H cases. There was a poor correlation between preoperative calcium and PTH values (R = 0.37) and both poorly correlated with the total gland volume (R < 0.40). Similarly, subgroup analysis using the number of involved glands showed poor correlation. The mean total gland volume was similar among all subgroups (SA = 1.28 cm³, DA = 1.43 cm³, and H = 1.27 cm³; P = .52), implying that individual glands were smaller in multigland disease. SA was found in 271 (53%) of patients with calcium levels of ≤10.5 mg/dL and 122 (78%) with levels of ≥12 mg/dL (P < .001).ConclusionThis is the largest series correlating preoperative calcium and PTH values with operative findings of gland size and number of diseased glands. Although a lower calcium value predicts somewhat more multigland disease, the overall poor correlation should make the parathyroid surgeon aware that gland size and multigland disease cannot be predicted by preoperative laboratory testing.     

Recombinant production of TEV cleaved human parathyroid hormone

The parathyroid hormone, PTH, is responsible for calcium and phosphate ion homeostasis in the body. The first 34 amino acids of the peptide maintain the biological activity of the hormone and is currently marketed for calcium imbalance disorders. Although several methods for the production of recombinant PTH(1‐34) have been reported, most involve the use of cleavage conditions that result in a modified peptide or unfavorable side products. Herein, we detail the recombinant production of ¹⁵N‐enriched human parathyroid hormone, ¹⁵N PTH(1‐34), generated via a plasmid vector that gives reasonable yield, low‐cost protease cleavage (leaving the native N‐terminal serine in its amino form), and purification by affinity and size exclusion chromatography. We characterize the product by multidimensional, heteronuclear NMR, circular dichroism, and LC/MS. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Bone Marrow Uptake in Parathyroid Scintigraphy is A Consequence of Extremely High Parathyroid Hormone Levels

ObjectiveWe retrospectively evaluated patients with end-stage renal disease (ESRD) who were referred to our department for parathyroid scintigraphy. The aim of this study was to investigate the causes of bone marrow uptake observed on parathyroid scintigraphy.MethodsWe included 18 ESRD patients (10 F, 8 M; mean, 52 ± 13 years old; range, 45-59) in the study. The disease duration of the patients was mean 7.7 ± 4.7 years. The patients’ mean plasma calcium and parathormone (PTH) levels were 9.7 ± 1.4 mg/dL and 1,553.3 ± 691.7 pg/mL, respectively. Dual-phase technetium-99m 2-methoxyisobutyl-isonitrile (Tc-99m MIBI) parathyroid imaging and, if necessary, additional Tc-99m pertechnetate scintigraphy were performed. Quantification of the planar early phase parathyroid images was performed for various regions (sternum, humerus, ribs) with the same size rectangular region of interest (ROI, 176 × 176 pixels). Average counts were compared with paired samples Student’s t tests, and P <.05 was considered statistically significant.ResultsTc-99m MIBI parathyroid imaging revealed parathyroid hyperplasia, adenoma, and ectopic adenoma in 7, 3, and 2 patients, respectively. The other 7 patients had normal scintigraphy results with regard to parathyroid pathologies. Bone marrow uptake in the sternum, ribs, and humerus was observed in 6 patients. The difference between the average quantitative value obtained from the ROIs drawn on the sternum and humerus was also statistically significant compared to patients without bone marrow uptake (P<.05). All 6 patients’ exhibited extremely high PTH levels (>2,000 pg/mL; mean, 2,413.7 ± 150 pg/mL) compared to the other 12 patients (mean, 1,342.8 ± 249 pg/mL).ConclusionOur results show that bone marrow uptake on parathyroid scintigraphy is a consequence of extremely high PTH levels in ESRD patients; no further analysis is required. (Endocr Pract. 2013;19:202-205)     

Elevation of PTH and PTHrp Induced by Excessive Fluoride in Rats on a Calcium-deficient Diet

Study on the role of parathyroid hormone (PTH) and parathyroid hormone-related peptide (PTHrp) in the process of skeletal fluorosis, involved especially in calcium deficiency, is rare. We evaluated the level of serum PTH and mRNA expression of PTHrp in femur when rats were exposed to excessive fluoride with low-calcium diet. Wistar rats (n = 60) was divided into four groups, a control group, fluoride group, low-calcium group, and low-calcium fluoride group. The fluoride groups were treated with fluoride by drinking tap water containing 100 mg F-/L. The low-calcium diet contained 0.05% calcium. Serum was collected in the first, fourth, eighth, and 12th of phase for the detemination of PTH and Ca²⁺. RNA extraction from femora was used to analyze the mRNA express of PTHrp, osteopontin (OPN), and osteocalcin (OCN) after 12 weeks of fluoride dosing. Results showed that serum PTH increased gradually with the extension of fluoride exposure, but Ca²⁺ decreased, both of which embodied a time-dependent relationship. Cotreatment of excessive fluoride with low-calcium diet largely stimulated the secretion of PTH. The low dietary calcium markedly increased mRNA expression of PTHrp in animals with fluoride treatment. Expression of OPN and OCN significantly increased in the rats treated with excessive fluoride and low-calcium diet. We demonstrated that fluoride by itself affected the body's calcium metabolism and stimulate the secretion of PTH. PTH may play an important role in anabolic effect of excessive fluoride on bone turnover of skeletal fluorosis and calcium deficiency exacerbated the action of PTH and PTHrp on the characteristic bone lesion of fluorosis.     

Cellular uptake of 3H-actinomycin D in the hematological tissues and liver of the mouse

Actinomycin D(AM), an inhibitor of DNA-dependent RNA synthesis, produces a reversible cessation of red blood cell production. This study examines the in vivo cellular uptake of ³H-AM in the hematological tissues and livers of B6D2F₁ mice. ³H-Am (sp. act. = 2.97 to 4.20 C/mmole) was given IV at a dose of 4.0 to 5.7 μg (14 μc) per mouse. Spleen, bone marrow, blood, and liver samples were taken for autoradiography at post-injection times of five minutes to 67 hours. We have confirmed the rapid in vivo cellular uptake of AM; substantial quantities of the drug were in the nuclei within five minutes of IV administration. Not all cell types became labeled. Erythroid, hepatic, lymphoid, and reticulo-endothelial (RE) cells and monocytes took up the label, whereas labeling of granulocytic elements was doubtful. Most heavily labeled were liver cells (highest mean grain count = 110.1) and splenic RE(19.1) and erythroid (16.1) cells. Erythroid cells in the spleen were more heavily and more rapidly labeled than those in the bone marrow. All nucleated erythroid maturational stages, in both the spleen and the bone marrow, were labeled, even at five minutes. The time course of erythroid and hepatic labeling was quite different. Whereas early erythroid cells required six hours to become 100% labeled, liver cells were 100% labeled at five minutes and loss of hepatic labeling began as early as 15 to 30 minutes.     

The effect of haemorrhage on the cell populations of the thymus and bone marrow in wild starlings (Sturnus vulgaris)

Summary Following the withdrawal of blood from the brachial vein of adult wild starlings (Sturnus vulgaris) changes in the cell populations within the bone marrow and thymus were observed over an eight day period. The packed cell volume, haemoglobin content and reticulocyte count of the peripheral blood was determined before and after haemorrhage.The maximum effect of the haemorrhage was observed in the bone marrow after four days when the population of small lymphocytes, and basophilic erythroid precursors were reduced to less than 1%. At the same time the percentage of another line of erythroid cells increased to 68%. This second erythroid lineage was the major erythroid line in the thymus, and again maximum representation occurred at 4 days post haemorrhage. After this the thymus became predominantly lymphoid and started to increase in size.The two erythroid lines are described and their status with regard to avian thrombocytes is also discussed.The peripheral blood had not attained the pre-haemorrhagic values for reticulocyte counts by eight days although the packed cell volumes and haemoglobin contents were similar.I would like to thank Dr. Peter Ward of the Institute of Terrestrial Ecology for help in obtaining the starlings. Thanks are also due to the staff of the Anatomy Department of St. Thomas's Hospital Medical School, and in particular Mr. Watson. This and other work on the thymus is possible due to the support of the Research (Endowments) Committee of St. Thomas's Hospital     

Parathyroid hormone co-stimulation of hepatocyte proliferation is sensitive to protein kinase A and calcium channel inhibitors

Parathyroid hormone (PTH) mobilises calcium in the hepatocyte, an effect which is abolished by verapamil and staurosporine. In our study parathyroid hormone was shown to act additively to dHGF in inducing hepatocyte DNA synthesis. It is also shown that PTH induced the production of inositol 1,4,5 trisphosphate (IP₃) andc-fos expression at early times in culture. Co-incubation of PTH and dHGF with ac-fos antisense oligodeoxynucleotide inhibited hepatocyte DNA synthesis, indicating that the additive effect of PTH is correlated with the induction ofc-fos. H-89, a PKA specific inhibitor, inhibited the PTH effect on IP₃ production as well as the PTH effect on hepatocyte DNA synthesis. Verapamil and staurosporine also inhibited the PTH effect in dHGF-induced DNA synthesis. Therefore it is suggested that PKA mediated at a great extent the co-stimulatory effects of PTH on hepatocyte proliferation via IP₃ production.     

Primary Hyperparathyroidism: Comparing Between Solid and Cystic Adenomas and the Efficacy of Ultrasound and Single-Photon Emission Computed Tomography in their Diagnosis

Objective: Primary hyperparathyroidism (PHPT) is a disorder that results from abnormal functioning of the parathyroid glands. The purpose of this study was to compare cystic and solid adenomas by analyzing different variables associated with PHPT and parathyroid adenomas (age, calcium, phosphorus, and parathyroid hormone &lsqb;PTH] levels, adenoma volume) while comparing the efficacy of ultrasound and single-photon emission computed tomography in differentiating between both types of adenoma.Methods: From 152 patients diagnosed with PHPT between January 2013 and 2014, only 109 patients who had positive ultrasonographic findings for single parathyroid adenoma were included in the study.Results: A total of 26 patients had cystic adenomas and 83 patients had solid adenomas. Sestamibi (MIBI) was negative in 50% of the cystic adenoma group and 27.7% of the solid adenoma group, with an overall technetium-MIBI efficacy of 67%. Age, phosphorus level, and adenoma volume were significantly higher in patients with cystic adenomas (P = .001, P = .02, and P = .02, respectively), whereas calcium and PTH levels were significantly higher in patients with solid adenomas (P = .02, P = .038, respectively). MIBI had a significant correlation with PTH levels (P = .031) and adenoma volume (P = .05) only in patients with solid adenomas. No significant correlation was found between sex and type of parathyroid adenoma.Conclusion: The current study is the first to compare age, PTH levels, and adenoma volume between cystic and solid adenoma patients, providing more information for the poorly understood pathology of cystic adenomas. Our findings showed that age and calcium and PTH levels are significantly higher in patients with solid adenomas, whereas adenoma volume and phosphorus levels are significantly higher in patients with cystic adenomas.Abbreviations: BMD = bone mineral density GFR = glomerular filtration rate iPTH = intact parathyroid hormone MIBI = sestamibi PHPT = primary hyperparathyroidism PTH = parathyroid hormone SPECT = single-photon emission computed tomography Tc = technetium US = ultrasound     

Characteristics of bovine parathyroid cell organoids in culture

Summary Adult bovine parathyroid glands were enzymatically dispersed and groups of 2 to 5 million cells were reassociated into multicellular aggregates (organoids) by rotation in roller tubes in serum-free medium. Fifty to seventy percent of the seeded cells were incorporated into each organoid at 3 d of culture, and in a typical experiment where DNA content was assayed before and after culture 49 ± 3% of the original seeded DNA was present after 19 d of culture. No significant differences in DNA content were observed between experimental groups at any time of culture. The morphology of the cells in organoids was similar to that of cells in fresh tissue as determined by light and electron microscopy. The organoids secreted intact parathyroid hormone (PTH) and COOH-terminal hormone fragments which were similar to those released from monolayer cell cultures. Organoids maintained the ability to modulate PTH secretion in response to extracellular calcium for over 2 wk in culture. Each organoid was cultured separately and secreted PTH such that the mean standard deviation of secretion within groups on a per organoid basis was 16.3% of the mean. Using a perifusion system to study acute regulation over a 2-wk period of culture, PTH secretion was suppressed 58±4% by 2.5 mM compared to that at 0.25 mM calcium. To examine PTH secretion over a range of calcium concentrations, the perifusion system was used to apply 4-h linear gradients of decreasing calcium to fresh tissue slices and to organoids. The results indicated that the calcium (ionized) concentration at 50% secretory suppression (set-point) were 1.30±0.11 and 1.20±0.9 mM for the organoids and slices, respectively. Acute secretory control by calcium decreased after 14 d and was not detectable at 22 d of culture. The results demonstrated that the organoids maintained their differentiated function and tissuelike morphology for extended periods in vitro and therefore represent a suitable model system for studies on the long-term modulation of PTH secretion by vitamin D metabolites, ions, and other agents. This work was supported by grant AM 18323 from the National Institutes of Health, Bethesda, MD. Portions of the work were presented at the Sixth Annual Scientific Meeting of the American Society for Bone and Mineral Research in Hartford, Connecticut, June 26–29, 1984.     

Identifying Parathyroid Hormone Disorders and their Phenotypes through a Bone Health Screening Panel: It's not Simple Vitamin D Deficiency!

Objectives: To determine the utility of bone health screening panels in identifying disorders of parathyroid gland secretions.Methods: A retrospective analysis of biochemical parameters in a bone health screening panel (BHSP) was conducted. Low and high cutoffs were applied to determine hypofunctioning and hyperfunctioning conditions related to parathyroid hormone. Clinical phenotypes of parathyroid gland abnormalities were determined using a combination of levels of calcium, 25-hydroxyvitamin D, and intact parathyroid hormone (iPTH). A PTH nomogram was applied to calculate the maximum expected PTH for existing levels of 25-hydroxyvitamin D. Medical records of patients were reviewed for clinical validation of biochemical findings.Results: Sixty-eight percent of subjects showed abnormal PTH secretion. Primary hyper- and hypoparathyroidism were detected in 1% (n = 5) and 0.4% (n = 2) of subjects, respectively. Normocalcemic hyperparathyroidism and hypercalcemia with inappropriately high-normal PTH were identified in 8.5% (n = 37) and 2% (n = 10) of subjects, respectively. All subjects with primary and normocalcemic hyperparathyroidism had higher measured PTH than calculated maximum PTH using the PTH nomogram. Secondary hyperparathyroidism and functional hypoparathyroidism were present in 18% (n = 88) and 39% (n = 194) of subjects, respectively. High prevalence of bone pains, renal stones, and low bone mineral density were identified in patients with abnormal PTH secretion.Conclusion: Panel testing is useful in early diagnosis of metabolic bone disorders related to PTH. A BHSP helps identify normocalcemic hyperparathyroidism and hypercalcemia with inappropriately high PTH.Abbreviations:25OHD = 25-hydroxyvitamin DAKUH = Aga Khan University HospitalBHSP = bone health screening paneliPTH = intact parathyroid hormonemaxPTH = maximum parathyroid hormoneMBD = metabolic bone diseaseNCHPT = normocalcemic hyperparathyroidismPHPT = primary hyperparathyroidismPTH = parathyroid hormoneSHPT = secondary hyperparathyroidismVDD = vitamin D deficiency     

Ca2+-Induced Increases in Steady-State Concentrations of Intracellular Calcium Are Not Required for Inhibition of Parathyroid Hormone Secretion

It has been well established that increases in extracellular calcium concentration ([Ca²⁺]) inhibit parathyroid hormone (PTH) secretion. The effects of [Ca²⁺] are mediated through a G-protein-coupled receptor that has been cloned and characterized. Additionally, it has been demonstrated in parathyroid cells that an increase in [Ca²⁺] results in an increase in steady-state levels of intracellular calcium ([Ca²⁺]_i). At present, it has not been fully resolved whether changes in [Ca²⁺]_i are related to changes in PTH secretion. In the current study, the effect of increased [Ca²⁺] on PTH secretion and the connection regarding changes in concentrations of intracellular calcium [Ca²⁺]_i have been examined in primary cultures of bovine parathyroid cells. PTH secretion was measured by radioimmunoassay and intracellular calcium was determined by single cell calcium imaging. Bovine parathyroid cells pre-incubated with either 0.5 or 1 mM calcium responded to rapid increases in [Ca²⁺] (≥0.5 mM) with an immediate and sustained increase in steady-state levels of [Ca²⁺]_i that persisted for time intervals greater than 15 minutes. Although the magnitude of the sustained increase in [Ca²⁺]_i varied among individual cells (∼40% to >300%), the overall pattern and course of time were similar in all cells examined (n = 142). In all trials, [Ca²⁺]_i immediately returned to baseline levels following the addition of the calcium chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA). Additional control studies, however, suggest that sustained increases in [Ca²⁺]_i do not correlate with regulation of parathyroid hormone secretion. Sustained elevations of [Ca²⁺]_i were not observed when [Ca²⁺] was gradually increased by the addition of 0.1 mM increments at 1 minute intervals. Furthermore, the effect on inhibition of PTH secretion was the same regardless of whether [Ca²⁺] was increased by gradual or rapid addition.     

Suppressibility of Parathyroid Hormone in Primary Hyperparathyroidism

ObjectiveTo describe an unusual case of pathologically confirmed primary hyperparathyroidism in a patient presenting with severe hypercalcemia and an undetectable parathyroid hormone (PTH) level.MethodsWe present a detailed case report and outline the serial laboratory findings. In addition, the possible causes of low serum PTH levels in the setting of primary hyperparathyroidism are discussed.ResultsA 16-year-old female patient presented with severe epigastric pain, found to be attributable to acute pancreatitis. At hospital admission, her serum calcium concentration was high (14.0 mg/dL); the patient also had a normal serum phosphorus level of 3.6 mg/dL and an undetectable PTH level (< 0.2 pmol/L). An evaluation for non-PTH-mediated causes of hypercalcemia revealed a partially suppressed thyroid-stimulating hormone concentration and a below normal 1,25-dihydroxyvitamin D level, consistent with her suppressed PTH. One week after the patient was dismissed from the hospital, repeated laboratory studies showed a serum calcium value of 11.1 mg/dL, a serum phosphorus level of 2.8 mg/dL, and an elevated PTH concentration of 11.0 pmol/L, consistent with primary hyperparathyroidism. A repeated 1,25-dihy-droxyvitamin D measurement was elevated. A parathyroid scan showed a parathyroid adenoma in the left lower neck area, and she subsequently underwent successful surgical resection of a pathologically confirmed parathyroid adenoma.ConclusionThis case demonstrates that the serum PTH level can be suppressed in patients with primary hyperparathyroidism. Moreover, it emphasizes the need for careful evaluation of the clinical context in which the PTH measurement is determined. Consideration should be given to repeating measurement of PTH and serum calcium levels when the initial laboratory evaluation of hypercalcemia is unclear because dynamic changes in calcium metabolism may occur in the presence of secondary contributing factors. (Endocr Pract. 2007;13:785-789)     

The roles of calcium and cyclic AMP in the stimulatory action of parathyroid hormone on thymic lymphocyte proliferation

Both the parathyroid hormone (PTH) and the calcium ion increase the cellular content of cyclic adenosine 3′,5′-monophosphate (cyclic AMP), promote the initiation of deoxyribonucleic acid synthesis and stimulate the proliferation of rat thymocytes maintained in vitro. The ability of cyclic AMP to serve as the mediator of the mitogenic actions of both PTH and calcium is established by the fact that cyclic AMP itself stimulates cell proliferation in the absence of PTH and extracellular calcium. Neither PTH nor calcium appear to raise the cellular cyclic AMP level by increasing the nucleotide's synthesis by adenylate cyclase (formerly adenyl cyclase); PTH concentrations as high as 50 μg per ml of medium do not increase the enzyme's activity (in the presence or absence of calcium) and mitogenic calcium concentrations inhibit it. PTH also does not directly affect isolated thymocyte phosphodiesterase, but mitogenic calcium levels inhibit the enzyme's activity. Additional experiments show that it is calcium which raises the cyclic AMP level in cells treated with PTH, and some possible calcium-mediated mechanisms by which the hormone could elevate the cellular cyclic AMP levels are discussed. Thus, the mitogenic action of PTH is primarily mediated by calcium while cyclic AMP is the ultimate implementor of the hormonal action. However, calcium has a dual role and evidence is presented which indicates that besides raising the cellular cyclic AMP level, it also controls the operation of cyclic AMP's mitogenic end-reaction.     

Three large, functioning cystic parathyroid adenomas

ObjectiveTo report a very rare case of 3 large, functioning cystic parathyroid adenomas causing primary hyperparathyroidism.MethodsWe present the history, clinical findings, laboratory test results, radiologic findings, endocrine workup results, intraoperative surgical challenges, and surgical pathology report of the study patient. We review the literature and discuss the importance of intraoperative parathyroid hormone (PTH) measurement in such cases.ResultsA 79-year-old woman presented with primary hyperparathyroidism and elevated levels of calcium and PTH. Localization studies confirmed the presence of a large right upper parathyroid adenoma. On exploration, a very large cystic parathyroid gland was identified at that location. Because intraoperative PTH levels remained elevated, further exploration was pursued, which revealed 2 more large cystic glands on the left side that were resected. This resulted in an adequate but slow PTH drop. The right lower gland appeared normal. On follow-up 4 days and 6 weeks after surgery, the calcium and PTH levels had normalized.ConclusionThis case highlights the aspects of intraoperative PTH use and underscores the need to exclude multigland disease even in the setting of a very large parathyroid cyst with concordant localization studies. (Endocr Pract. 2012;18:e14-e16)     

Tumor Volume Can Be Used as a Parameter Indicating the Severity of Disease in Parathyroid Cancer

ObjectiveTo determine whether tumor volume and tumor size are related to disease severity in parathyroid cancer (PC).MethodsPatients treated for PC at our institution were retrospectively identified. Data were collected about clinical and pathologic characteristics, laboratory parameters, tumor volume, recurrence, metastasis, and mortality. Correlation analysis was applied to laboratory parameters, tumor volume, and tumor size in PC patients.ResultsThe study included 20 patients diagnosed with PC at our center. The median follow-up was 33 months. Serum calcium (median, 12.5 mg/dL), serum parathormone (PTH) (median, 743 pg/mL), and serum alkaline phosphatase (ALP) (median, 298 U/L) levels were found to be increased, and 25-hydroxyvitamin D (25[0H)D) (median, 12.3 ng/mL) and serum phosphorus (median, 2.1 mg/dL) levels were decreased. Magnesium level was within normal limits (median, 1.9 mg/dL). The median tumor volume was 5.7 mL and median tumor size was 2.5 cm. Significant positive correlations were found between tumor volume and calcium, ALP, and PTH levels. A significant negative correlation was found between tumor volume and 25(OH)D level. There were no significant correlations between tumor size and calcium, ALP, PTH, and 25(OH)D.ConclusionThese results found that the tumor volume affected PTH, calcium, ALP, and 25(OH)D levels. The morbidity and mortality associated with PC were usually associated with PTH secretion and hypercalcemia. Therefore, tumor volume may be a more effective parameter than tumor size when evaluating the severity of disease.     

A Retrospective Study of Ultrasonography in the Investigation of Primary Hyperparathyroidism: A New Perspective for Ultrasound Echogenicity Features of Parathyroid Nodules

ObjectiveTo identify and understand parathyroid lesions of patients with primary hyperparathyroidism (PHPT) more accurately under ultrasound.MethodsThis retrospective study involved 423 adult patients with PHPT with a single parathyroid nodule and positive parathyroid ultrasonography between 2018 and 2019. The clinical characteristics of the study patients and histopathologic sections were reviewed.ResultsAccording to the main grayscale echogenicity features of parathyroid nodules, 423 cases were divided into groups: iso-hyperechogenicity solid (61/423), hypoechogenicity solid (304/423), and mixed-echogenicity cyst-solid (58/423) groups. Comparison among the 3 groups showed that the iso-hyperechogenicity group included more asymptomatic patients with PHPT and fewer patients with severe symptoms like bone fractures (P < .05). The mixed-echogenicity group showed higher median serum parathyroid hormone (PTH) and serum calcium levels and larger lesion sizes (P < .05), and the iso-hyperechogenicity group showed the lowest median serum PTH level. No difference in lesion size was noted between the 2 solid groups, but the median serum PTH level in the hypoechogenicity group was higher than that in the iso-hyperechogenicity group (P < .05). According to histopathology, the hypoechogenic area of the samples may contain more functional components (chief cells), whereas the iso-hyperechogenic area has more nonfunctional components (eg, lipocytes and connective tissues).ConclusionThe PHPT nodules distinguished by ultrasound echogenicity features showed different histopathologic components, reflected by different clinical characteristics of the patients with PHPT.     

Direct and indirect assessment of the parathyroid hormone response to pamidronate therapy in Paget's disease of bone and hypercalcaemia of malignancy

In patients with either Paget's disease or hypercalcaemia associated with malignancy (HCM) we have assessed the parathyroid response to pamidronate therapy, both by immunoassay of serum intact parathyroid hormone PTH (1–84) and by measurement of indirect parameters of PTH bioactivity, tubular maximum reabsorption of phosphate (TmPO₄/GFR) and nephrogenous cyclic AMP (NcAMP).In 12 patients with Paget's disease, therapy with pamidronate produced a small but significant decrease in adjusted serum calcium within the reference interval which was accompanied by a progressive increase in PTH (1–84) secretion and a corresponding fall in TmPO₄/GFR and increase in NcAMP.In 12 patients with HCM pretreatment, PTH (1–84) concentrations were suppressed, whilst mean TmPO₄/GFR was reduced and NcAMP was increased, compatible in most patients, with parathyroid hormone-related peptide (PTHrP) driven hypercalcaemia. Therapy with pamidronate produced the expected fall in serum calcium but caused an increase in PTH (1–84) secretion in the presence of absolute hypercalcaemia. The initial subnormal TmPO₄/GFR decreased further to a nadir on day 5, and there was a corresponding further increase in NcAMP. By day 7, however, when PTH (1–84) concentrations were maximal, there was a significant paradoxical rise in TmPO₄/GFR and a corresponding decrease in NcAMP.These data are consistent with a variable trigger point for PTH (1–84) secretion, one consequence of which is a reduction in the risk of hypocalcaemia following pamidronate.The results have major clinical implications for the interpretation of PTH (1–84) measurements in patients who are being treated or about to be treated for bone disease or for hypercalcaemia of malignancy (HCM). A pretreatment sample is essential in making the correct diagnosis in such patients, preventing confusion and possible unnecessary investigation.     

Defective regulation of the cytosolic Ca2+ activity in parathyroid cells from patients with hyperparathyroidism

The parathyroid hormone (PTH) release and cytosolic Ca²⁺ activity were determined in normal bovine parathyroid cells and parathyroid cells obtained from patients with hyperparathyroidism (HPT). There was a sigmoid relation between the cytosolic Ca²⁺ activity and the extracellular calcium concentration between 0.5 and 6.0 mmol/l. The PTH release was inhibited in parallel with the rise in the cytosolic Ca²⁺ activity. Both the hormone release and the cytosolic Ca²⁺ activity were lower in cells from human adenomas and hyperplastic glands~ and in comparison with the bovine preparations these ceils had higher set points for the cytosolic Ca²⁺ activity and PTH release. There was a close correlation between the individual set points for the cytosolic Ca²⁺ activity and PTH release in a material containing both normal and pathological cells. The results indicate that the abnormal PTH release characteristic of HPT is due to a defective regulation of the cytosolic Ca²⁺ activity.     

Thymus-associated parathyroid hormone has two cellular origins with distinct endocrine and immunological functions

In mammals, parathyroid hormone (PTH) is a key regulator of extracellular calcium and inorganic phosphorus homeostasis. Although the parathyroid glands were thought to be the only source of PTH, extra-parathyroid PTH production in the thymus, which shares a common origin with parathyroids during organogenesis, has been proposed to provide an auxiliary source of PTH, resulting in a higher than expected survival rate for aparathyroid Gcm2 ^−/− mutants. However, the developmental ontogeny and cellular identity of these “thymic” PTH–expressing cells is unknown. We found that the lethality of aparathyroid Gcm2 ^−/− mutants was affected by genetic background without relation to serum PTH levels, suggesting a need to reconsider the physiological function of thymic PTH. We identified two sources of extra-parathyroid PTH in wild-type mice. Incomplete separation of the parathyroid and thymus organs during organogenesis resulted in misplaced, isolated parathyroid cells that were often attached to the thymus; this was the major source of thymic PTH in normal mice. Analysis of thymus and parathyroid organogenesis in human embryos showed a broadly similar result, indicating that these results may provide insight into human parathyroid development. In addition, medullary thymic epithelial cells (mTECs) express PTH in a Gcm2-independent manner that requires TEC differentiation and is consistent with expression as a self-antigen for negative selection. Genetic or surgical removal of the thymus indicated that thymus-derived PTH in Gcm2 ^−/− mutants did not provide auxiliary endocrine function. Our data show conclusively that the thymus does not serve as an auxiliary source of either serum PTH or parathyroid function. We further show that the normal process of parathyroid organogenesis in both mice and humans leads to the generation of multiple small parathyroid clusters in addition to the main parathyroid glands, that are the likely source of physiologically relevant “thymic PTH.”     

Associations of Serum Ionized Calcium,Phosphate, and Pth Levels with Parathyroid Scan in Primary Hyperparathyroidism

Objective: To evaluate the relationship between various biochemical parameters in patients with primary hyperparathyroidism (PHPT) with positive and negative technetium-99 sestamibi (Tc) parathyroid scans performed with single-photon emission computed tomography/computed tomography (SPECT/CT).Methods: This retrospective analysis was used to develop a logistic probability model. It included 218 patients with PHPT. The main outcome measures were serum total calcium, ionized calcium, intact parathyroid hormone (PTH), albumin, alkaline phosphatase, phosphate, 25-hydroxy vitamin D, 1,25-dihydroxy vitamin D, 24-h urinary calcium levels, and parathyroid adenoma weight.Results: Individually, using cut-off levels of 6.0 mg/dL for ionized calcium, 3.0 mg/dL for phosphate, and 90 pg/mL for intact PTH, we found that 91.3% (P = .005), 70.7% (P = .004) and 87.90% (P = .023) of the patients had a positive Tc scan with their corresponding strengths of associations in the parentheses. Similar significant associations were sustained in multivariate setting for serum ionized calcium (P = .015), phosphate (P = .016), and intact PTH (P = .028). A logistic probability model was designed to predict the probability of being positive for Tc scan given a set of covariates.Conclusion: There are significant associations between the levels of serum ionized calcium, phosphate, intact PTH, and Tc scan positivity. Further studies with larger patient populations are needed.Abbreviations: BMI = body mass index; CT = computed tomography; CV = coefficient variation; DXA = dual-energy x-ray absorptiometry; MRI = magnetic resonance imaging; PHPT = primary hyperparathyroidism; PPV = positive predictive value; PTH = parathyroid hormone; SPECT = single-photon emission computed tomography; Tc = technetium-99 sestamibi