Forms Of Hyperparathyroidism Research Articles

Correlation of localization and size of the parathyroid glands by ultrasound and intraoperative findings in hyperparathyroidism

<p><strong>Aim <br /></strong>To determine a correlation between the localization of the parathyroid gland (PTG), based on ultrasound (US) examination and the operative findings, as well as the correlation between the size of the parathyroid glands measured by ultrasonography (USG) with pathological findings+, and prevalence of enlarged parathyroid glands in various forms of hyperparathyroidism.<br /><strong>Methods<br /></strong> A total of 83 patients with hyperparathyroidism who had undergone parathyroidectomy over a period of seven years<br />were included in the study. US examinations of the neck and scintigraphy were performed before surgery in 83 and 42 patients, respectively. In the pathohistological analysis, in addition to diagnosis, the size and weight of the parathyroid gland were measured.<br /><strong>Results</strong> <br />US examination revealed 125 enlarged parathyroid glands and two normal-sized glands. Scintigraphy revealed 52 enlarged and three normal-sized parathyroid glands. Enlarged parathyroid glands were more frequently found in the projection of the lower pole thyroid glands. A significantly higher number of enlarged upper parathyroid glands were found by the operative findings than by US. There was no statistically significant difference in the diagnosis of enlarged parathyroid glands in all three forms of hyperparathyroidism. There was a positive correlation between the<br />size of the parathyroid glands obtained by US and the size of the operative finding (κ=0.51; p=0.00 and p<0.0005, respectively). The relationship between parathyroid gland size measured by ultrasound and pathological analysis showed a positive correlation.<br /><strong>Conclusion</strong> <br />Ultrasound was useful in evaluating enlarged parathyroid glands, especially in combination with scintigraphy.</p>

PARATHYROIDECTOMY IN PATIENTS WITH HYPERPARATHYROIDISM

Aim: The aim of this study was to analyze all the factors (disease symptoms, sinthigraphic findings, biochemical parameters) that occur in patients with hyperparathyroidism, and since hyperparathyroidism itself is a common endocrine disorder. Methods: We analyzed 79 patients with primary, secondary, and tertiary hyperparathyroidism, who underwent surgery. We analyzed mean of age, male: female ratio, representation of different forms of hyperparathyroidism. In our study, we examined the indications for examination and surgery, as well as the most common symptoms and comorbidities. For localization PTG, scintigraphy was performed by a nuclear medicine specialist (at the Clinic of Radiology and Nuclear Medicine) preoperatively. Preoperative values of calcium (Ca), phosphorus (P), and parathyroid hormone (PTH) were determined in all patients, and the same values were measured postoperatively. We also analyzed correlation of dialysis length and parathyroid gland hyperplasia in patients with secondary hyperparathyroidism. Results: In our study mean of years was 51.13 ± 11.83 and most of the respondents were female. The most common operation was subtotal parathyroidectomy. The most common indication for examination of parathyroid glands (PTG) was renal failure. The most common comorbidity was arterial hypertension, which was found in 43 (53.2%) subjects, and the rarest gastrointestinal diseases and pancreatitis, in 1 (1.3%) patients. Scintigraphy showed an equal representation of enlarged lower parathyroid glands (both right and left). The mean values determined preoperatively for PTH were 796.24 pg/ml, Ca 2.58 mmol / l and P 1.35 mmol / l. The mean postoperative values for PTH were 222.33 pg/ml, Ca 2.06 mmol/l and P 1.17 mmol/l. We also showed that was a large correlation between dialysis length and hyperplasia. Conclusion: Hyperparathyroidism is a common endocrine disease, carrying potential complications of many organic systems. In most cases, regardless of the form (primary, secondary, or tertiary), it ultimately requires surgical treatment. For this reason, the clinical picture must be well known, the necessary preoperative diagnostic methods (which are complex), all with the aim of better effect of treatment of such patients.

Hyperparathyroidism and Vitamin D: Relationship Difficulties

Hyperparathyroidism is a clinical and laboratory syndrome characterized by hyperproduction of parathyroid hormone (PTH) by cells of the parathyroid glands (PTG) and is subdivided, depending on the cause of its occurrence, into primary (PHPT), secondary (SHPT) and tertiary hyperparathyroidism (THPT). To date, only a few scientific papers have been published on the features of the relationship between vitamin D and various forms of hyperparathyroidism, there may be several reasons for this. First, this is due to the fact that the true prevalence of vitamin D deficiency in hyperparathyroidism is unknown. Secondly, difficulties in the differential diagnosis of hyperparathyroidism sometimes entail not always justified surgical intervention with the potential development of complications, which, of course, is a rather narrow area of interest, both in endocrinology in particular and in medicine in general. Thirdly, the asymptomatic, often hidden, latent nature of the variety of multiple organ clinical manifestations of hyperparathyroidism, in combination with low levels of 25(OH)D, as the disease progresses, can lead to a significant decrease in the quality and life expectancy of patients. The combination of these arguments prompted us to summarize all the data available to date on the complexity of the relationship between vitamin D and various forms of hyperparathyroidism.

The accuracy of ultrasonography for detection of enlarged parathyroid glands in patients with different forms of hyperparathyroidism

Background/Aim. Ultrasonography is a cheap, easily available and convenient method for diagnosis. The aims of this study were: to determine the utility of ultrasonography for preoperative identification and localization of enlarged parathyroid glands (PTG) in patients with different forms of hyperparathyroidism (HPT); to examine the frequency of PTG detection in patients previously non-suspected for HPT but having symptoms relevant to the disease; to determine sensitivity and positive predictive value (PPV) of ultrasonography for identification of PTG in HPT and to compare obtained results with those obtained by scintigraphy. Methods. This investigation was designed as a retrospective?prospective study. The total number of patients undergoing ultrasonography prior to surgery was 179 and the number of those subjected to scintigraphy, mostly by the 201Tl/99mTc method, was 112. The patients (52 male, 128 female) were divided into the following four groups: group A ? patients with primary (p)HPT (n = 78); group B ? patients with secondary (s)HPT (n = 47); group C ? patients with tertiary (t)HPT (n = 13); group D ? patients with unrecognized (u)HPT, but with anamnestic data implying the disease (n = 42). High resolution ultrasonography was performed by a single experienced observer. Diagnosis of HPT was based on characteristic clinical and biochemical parameters. Final proof of HPT diagnosis was surgery followed by histopathological examination. Results. Ultrasonography detected enlarged PTG in 93.85% of total patients, whereas scintigraphy uncovered 75.89% of positive cases (p < 0.05). The total number of positive PTG detected by ultrasonography was 211 vs 225 detected by surgery (sensitivity ? 95.9%; PPV ? 99.4%). Histopathology confirmed the predominance of adenoma in the A and D groups in comparison with the B group of patients having PTG hyperplasia. The group C was characterized by the presence of adenomas in hyperplastic PTG. The mean size of PTG measured by ultrasonography was 17.59 ? 8.0 mm (n = 164) vs 18.36 ? 8.54 mm (n = 179) measured after surgery. Ultrasonography proved itself as an accurate technique in all HPT groups, regarding its high sensitivity (range 93.6?100%) and PPV (95.6?100%). In contrast, scintigraphy was shown to be less reliable, especially in the sPTH group (sensitivity: 51.7%; PPV: 78.4%). Conclusion. Ultrasonography is more sensitive and accurate method for pre-operative localization of PTG in comparison with 201Tl/99mTc scintigraphy. It can be also efficiently used for detection of PTG and diagnosis of HPT in patients previously not suspected for this disease.

BONE SEVERE FORM OF HYPERPARATHYROIDISM IN A PATIENT WITH ADENOMA OF PARATHYROID GLAND

Hyperparathyroidism is one of the most common endocrinopathies. This disease leads to a violation of phosphorus-calcium metabolism and the washing out of calcium from bone tissue. Breach of the skeleton’s structure in hyperparathyroidism is often mistaken for metastatic bone damage, which leads to incorrect treatment tactics. In this work we present the clinical observation of a patient with an adenoma of the parathyroid gland and a severe bone form of hyperparathyroidism. Multiple lesions of bones with destruction of the cortical layer and the presence of the softtissue component were initially regarded as metastases in the bone. However, the morphological pattern of bone foci, as well as an elevated level of calcium and parathyroid hormone, made it possible to diagnose the bony form of hyperparathyroidism. The search for the cause of hyperparathyroidism revealed a tumor in the projection of the right lower parathyroid gland. Surgical removal of parathyroid adenoma led to the normalization of the level of calcium and parathyroid hormone. The article presents data of laboratory-instrumental methods of research and the results of surgical treatment of a patient.

Secondary and tertiary hyperparathyroidism in chronic kidney disease

In the treatment of secondary hyperparathyroidism of end-stage chronic kidney disease, vitamin D receptor activation and allosteric modulators of the calcium-sensing receptor – inhibit glandular hyperplasia, reduce parathyroid hormone levels, impact on bone turnover and mineral density. But the use of calcimimetic and vitamin D analogs or mimetics did not reduce the need for parathyroidectomy for refractory hyperparathyroidism. The enlarged parathyroid gland and gland nodular transformation became refractory to medical therapy and patient need for parathyroidectomy. Tertiary hyperparathyroidism is a state of excessive secretion of parathyroid hormone after a long period of secondary hyperparathyroidism and renal transplantation.
 In this article, we present the case of a Caucasian male with chronic kidney disease (end-stage on chronic hemodialysis and after kidney transplantation) and different forms of hyperparathyroidism (secondary and tertiary). Our case study shows that only a multi-interventional strategy is likely to be more effective treatment in cases of severe and refractory to medical therapy hyperparathyroidism.

Parathyroid carcinoma: A rare cause of primary hyperparathyroidism

Aim-background Parathyroid carcinoma is an exceedingly rare endocrine malignancy. Patients usually present with a severe form of hyperparathyroidism. Herein, we present a rare case of parathyroid carcinoma and hypercalcaemic crisis.

The Use of Calcimimetics for the Treatment of Secondary Hyperparathyroidism: A 10 Year Evidence Review.

Until the discovery of calcimimetics, the management of secondary hyperparathyroidism (SHPT) relied exclusively on treatment with phosphate binders, vitamin D derivatives or surgical parathyroidectomy with limited success. The therapeutic use of calcimimetic agents, together with a better understanding of the pivotal role of the calcium-sensing receptor (CaSR) in the physiological regulation of parathyroid gland function, substantially advanced the management of hyperparathyroidism in dialysis practice. Calcimimetics bind selectively to the CaSR receptor in parathyroid tissue and enhance the inhibitory effect of extracellular calcium ions on parathyroid hormone (PTH) secretion, thereby reducing PTH levels even when serum calcium concentrations are normal or low. The availability of calcimimetic agents for clinical use has opened a new era in the management of patients with SHPT. Indeed, calcimimetic compounds have been shown to reduce PTH levels and to lower serum calcium concentrations in all forms of hyperparathyroidism, including primary hyperparathyroidism (PHPT) and parathyroid carcinoma. Such findings underscore the critical importance of the CaSR as a therapeutic target in this family of clinical disorders. New calcimimetic agents are being developed that have the potential to offer improved efficacy and safety compared with currently available calcimimetic compounds.

Primary hyperparathyroidism having multiple Brown tumors mimicking malignancy

Primary hyperparathyroidism is a disease characterized by excessive secretion of parathormone. During the course of this disease, bone loss occurs, particularly depending on resorption of the skeletal system. One of the complications of primary hyperparathyroidism is fibrotic, cystic bony changes which is called Brown tumor. Skeletal manifestations in the form of Brown tumors are rare and according to literature occur in less than 2% of patients suffering from any form of hyperparathyroidism. Such rare and multiple benign lesions may simulate a malignant neoplasm and pose a real challenge for the clinician in its differential diagnosis. We present a case of a 23-year-old Indian woman who was evaluated for multiple lytic expansile lesions with a strong suspicion of malignancy and fibrous dysplasia but turned out to be a case of primary hyperparathyroidism.

A mathematical model of calcium and phosphorus metabolism in two forms of hyperparathyroidism

Parathyroid hormone (PTH) plays a critical role in calcium and phosphorus metabolism. Interestingly, in two forms of hyperparathyroidism (excessive amount of PTH in the serum), the metabolic disturbances in patients with chronic kidney disease (CKD) significantly differ from those with primary hyperparathyroidism (PHP). Since an intuitive understanding of these PTH-linked regulatory mechanisms are hardly possible, we developed a mathematical model using clinical data (1586 CKD and 40 PHP patients). The model was composed of a set of ordinary differential equations, in which the regulatory mechanism of PTH together with other key factors such as 1,25-Dihydroxyvitamin D (1,25(OH)₂D) and calcium was described in the tissues including bone, the kidney, the serum, and the parathyroid glands. In this model, an increase in PTH was induced by its autonomous production in PHP, while PTH in CKD was elevated by a decrease in feedback inhibition of 1,25(OH)₂D in the serum, as well as an increase in stimulation by phosphorus in the serum. The model-based analysis revealed characteristic differences in the outcomes of hyperparathyroidism in CKD and PHP. The calcium exchange in bone, for instance, was predicted significantly higher in PHP than CKD. Furthermore, we evaluated the observed and predicted responses to the administration of calcimimetics, a recently developed synthetic drug that modulated efficacy of calcium-sensing receptors. The results herein support the notion that the described model would enable us to pose testable hypotheses about the actions of PTH, providing a quantitative analytical tool for evaluating treatment strategies of PHP and CKD.

Primary Hyperparathyroidism Masquerading Malignancy: A Case Report

Skeletal manifestations in the form of brown tumors are rare and according to literature occur in less than 2% of patients suffering from any form of hyperparathyroidism. Such rare and multiple benign lesions may simulate a malignant neoplasm and pose a real challenge for the clinician in its differential diagnosis. We present a case that was evaluated for multiple lytic lesions with a strong suspicion of malignancy but turned out to be a case of primary hyperparathyroidism. doi:10.4021/jmc2010.07.106e

Clinical utility of calcimimetics targeting the extracellular calcium-sensing receptor (CaSR)

Calcimimetics, which activate the extracellular calcium (Cao2+)-sensing receptor in the parathyroid and other tissues participating in Cao2+ homeostasis, were the first described allosteric activators of a G-protein-coupled receptor. Cinacalcet, the only calcimimetic currently approved for human use, is used clinically for treating secondary hyperparathyroidism (e.g., overactivity of parathyroid glands) in patients being dialyzed for chronic kidney disease. By sensitizing the parathyroids to Cao2+, cinacalcet lowers the circulating parathyroid hormone (PTH) level. It also reduces serum calcium and phosphate, changes increasing the percentage of patients achieving the guidelines recommended by the National Kidney Foundation (NKF) for these minerals. Studies are underway addressing whether better adherence to these guidelines in patients receiving cinacalcet reduces cardiovascular disease and related mortality, which are both common is the dialysis population. The second approved use of cinacalcet is for treating hypercalcemia in patients with inoperable parathyroid carcinoma. In this setting, it provides the first medical therapy chronically lowering serum calcium concentration in this condition, albeit not to normal in most patients. Its effect on the long-term prognosis of these patients, if any, is presently unclear. “Off-label” administration of cinacalcet [i.e., not yet approved by the US Food and Drug Administration (FDA)] effectively lowers serum calcium and/or PTH in various other forms of hyperparathyroidism and increases serum phosphate in renal phosphate-wasting syndromes by reducing PTH-induced phosphaturia. In the future, the drug could conceivably be utilized to modulate the activity of the CaSR in other tissues (i.e., kidney, colon) in therapeutically desirable ways.

Primary Hyperparathyroidism Masquerading Malignancy: A Case Report

Skeletal manifestations in the form of brown tumors are rare and according to literature occur in less than 2% of patients suffering from any form of hyperparathyroidism. Such rare and multiple benign lesions may simulate a malignant neoplasm and pose a real challenge for the clinician in its differential diagnosis. We present a case that was evaluated for multiple lytic lesions with a strong suspicion of malignancy but turned out to be a case of primary hyperparathyroidism. J Med Cases. 2010;1(1):27-28 doi: https://doi.org/10.4021/jmc2010.07.106e

Adenomatous Human Parathyroid Cells Exhibit Impaired Sensitivity tol-Amino Acids

Primary hyperparathyroidism, which occurs most commonly in patients with adenomatous disease of a single parathyroid gland, arises as a result of impaired extracellular Ca(2+) (Ca(2+)(o))-dependent feedback on PTH secretion, a process mediated by the calcium-sensing receptor (CaR). Because the Ca(2+)(o) sensitivity of the CaR is positively modulated by L-amino acids, we decided to investigate whether the impaired feedback of PTH secretion in adenomatous parathyroid cells might arise from decreased sensitivity to L-amino acids. Samples of normal and adenomatous human parathyroid cells were prepared by collagenase treatment and then exposed in vitro to various concentrations of Ca(2+)(o) or the CaR-active amino acid, L-phenylalanine (L-Phe). Excess normal parathyroid tissue was obtained from parathyroid autotransplants at the time of thyroid surgery. Samples of adenomatous tissue were obtained from histologically confirmed parathyroid adenomas. The primary measure was sensitivity of Ca(2+)(o)-dependent PTH secretion to the amino acid L-Phe. The secondary measure was sensitivity of Ca(2+)(o)-dependent intracellular Ca(2+) mobilization to L-Phe. Parathyroid adenomas exhibited reduced sensitivity to the CaR-active amino acid L-Phe, which affected both Ca(2+)(o)-dependent PTH secretion and Ca(2+)(o)-dependent intracellular Ca(2+) mobilization as a measure of CaR-dependent signaling in parathyroid cells. Impaired L-amino acid sensing by calcium-sensing receptors in adenomatous parathyroid cells contributes to the loss of feedback control of PTH secretion in primary hyperparathyroidism. The CaR's amino acid binding site may be exploited as a target in the medical treatment of primary and perhaps other forms of hyperparathyroidism.

Therapeutic Use of Calcimimetics

It has long been recognized that the secretion of PTH by chief cells in the parathyroid gland is regulated by extracellular ionized calcium. The molecular mechanism by which extracellular Ca2+ performs this feat was deduced by the cloning of the extracellular calcium-sensing receptor (CaSR) in 1993 in the laboratories of Brown and Hebert. The CaSR is a G protein-coupled cell surface receptor that belongs to family 3 of the GPCR superfamily. The CaSR senses the extracellular ionic activity of the divalent minerals Ca2+ and Mg2+ and translates this information, via a complex array of cellular signaling pathways, to modify cell and tissue function. Genetic studies have demonstrated that the activity of this receptor determines the steady-state plasma calcium concentration in humans by regulating key elements in the calcium homeostatic system. CaSR agonists (calcimimetics) and antagonists (calcilytics) have been identified and have provided both current and potential therapies for a variety of disorders. Calcimimetics can effectively reduce PTH secretion in all forms of hyperparathyroidism. They are likely to become a major therapy for secondary hyperparathyroidism associated with renal failure and for treatment of certain patients with primary hyperparathyroidism. On the therapeutic horizon are calcilytics that can transiently increase PTH and may prove useful in the treatment of osteoporosis.

Derangement of glucose metabolism in hyperparathyroidism.

The derangement of glucose metabolism is found frequently in all forms of hyperparathyroidism. Both in primary (PHPT) and secondary hyperparathyroidism (SHPT) PTH excess is thought to be involved in deteriorating insulin sensitivity and secretion though their different clinical and pathophysiological conditions. In PHPT these abnormalities are related to a high frequency of Type 2 diabetes mellitus and also impaired glucose tolerance according to recent clinical studies, without differences between symptomatic and asymptomatic clinical presentation. In chronic renal failure (CRF), the disorders of glucose metabolism due to SHPT do not bear an increased risk for diabetes whereas they seem to be involved in the progression of atherosclerotic vascular damage which connotes CRF. Moreover, clinical and experimental studies have shown that vitamin D deficiency associated with glucose metabolism abnormalities favors the development of the metabolic syndrome. The potential for metabolic and cardiovascular harm related to hyperparathyroidism, especially PHPT, is the most interesting issue for clinical endocrinologists. This short review of the clinical and pathophysiological data of literature on glucose homeostasis disorders in hyperparathyroidism focuses on its potential clinical and therapeutic impact, particularly in the management of PHPT.

Tumor pardo óseo como primera manifestación de hiperparatiroidismo primario

AbstractWe report a clinical case of a 26 years old female who had a 2 years evolution chin tumour with hypercalcemia (11,8 mg/dl) and PTH (paratohormone) of 761 pg/ml. She underwent a CT scan and MRI of the mandible, as well as a biopsy followed by excision of the tumour by the maxilofacial surgeons. Our ENT Department asked for a Scintigraphy (Tc99s-mibi) and thoraciccervical CT, which showed a lesion that turned out to be an adenoma of the lower right parathyroid gland after sugery and pathological examination. The patient suffered a Primary hyperparathyroidism that was the main stimulus for the Brown Tumour made up by macrophagos and multinuclear giant cells, being this the first manifestation of the metabolic disorder. This form of hyperparathyroidism is very rare in the clinic. We do a literature review to establish the differential diagnosis for such pathology.

Utility of 99mTc‐sestamibi scintigraphy as a first‐line imaging procedure in the preoperative evaluation of hyperparathyroidism

The use of preoperative imaging in patients with hyperparathyroidism remains controversial. Many of the available techniques are insufficiently sensitive and specific to justify their routine use. We have evaluated the sensitivity and specificity of 99mTc-sestamibi scintigraphy in the management of patients with different forms of hyperparathyroidism. Preoperative imaging evaluation was carried out by scintigraphic detection of pathological parathyroid glands using 99mTc-sestamibi as a radiotracer; confirmation of scan findings was obtained surgically. A group of 25 patients with primary (n = 21) or secondary (n = 4) hyperparathyroidism were studied. All were considered for surgical treatment. In all cases parathyroid imaging was carried out by 99mTc-sestamibi scintigraphy together with at least one other imaging technique which included CT-scan, ultrasonography, MRI or 201TI/99mTc subtraction scintigraphy. Blood tests included measurements of total calcium and PTH. 99mTc-sestamibi scintigraphy correctly localized 20 out of 21 adenomas, giving a sensitivity of 95.2%, markedly higher than that obtained with the other imaging techniques (ultrasonography 75%, 201TI/99mTc subtraction scintigraphy 57.1%, CT-scan 41.7% and MRI 33%). Of a total of 17 glands identified surgically as hyperplastic and confirmed by pathological examination, 99mTc-sestamibi scintigraphy showed a positive image in 10, corresponding always to the larger abnormal glands (sensitivity 58.8%, higher than that observed with the other techniques). No false positive images were obtained with 99mTc-sestamibi. All the ectopic adenomas (n = 3) were identified preoperatively, which contributed significantly to the surgical approach. In patients with hyperparathyroidism, 99mTc-sestamibi scintigraphy may be used as the single imaging technique as it shows a very high sensitivity and specificity in the preoperative localization of pathological parathyroid glands; the benefit of localizing parathyroid tissue prior to surgery in cases of ectopic adenomas clearly indicates that when an imaging procedure is required, this technique may be of great help in the management of hyperparathyroidism.

Incidental preclinical hyperparathyroidism identified during thyroid operations

The entity of preclinical hyperparathyroidism has never been clearly investigated. The authors believe that the incidence of pathologic abnormalities of the parathyroid glands before the development of any symptoms or hypercalcemia (serum calcium > 12.0 mg/dl) is more frequent than has been reported. Over a 14-year period, parathyroid glands were examined during thyroid operations in over 800 patients. Serum calcium and phosphorous levels were measured in all patients preoperatively. Thirty-six patients had additional parathyroid operations for a preclinical form of hyperparathyroidism, defined by abnormal appearing parathyroid glands at the time of thyroid surgery. None of the 36 patients had symptoms of hyperparathyroidism preoperatively. Nine patients had borderline hypercalcemia (serum calcium 10.6 to 12.0 mg/dl), and the remainder were considered normocalcemic. The average age was 53 (range 21 to 75) with a male to female ratio of 1:3. Nine of the 36 patients had thyroid cancer. There were eight patients with parathyroid adenoma and 28 patients with parathyroid hyperplasia. Of 13 patients who had a history of neck irradiation, five had parathyroid adenoma and eight had parathyroid hyperplasia. Only two patients with parathyroid hyperplasia remain on calcium medication. Since preoperative normocalcemia does not preclude the presence of parathyroid pathology, the authors urge careful identification and examination of the parathyroid glands during thyroid operations. It adds little time to the procedure. Excision of parathyroid disease along with the thyroid gland can be performed safely and prevents the need for further operation with its associated morbidity.

Surgical Embryology and Anatomy of the Thyroid and Parathyroid Glands

A thorough knowledge of parathyroid embryology and anatomy is essential for maximum success in restoration of calcium homeostasis in those patients who have a form of hyperparathyroidism. In fact, an initial meticulous neck dissection by a competent parathyroid surgeon who is well versed in the embryology and anatomy of the neck is the current "hi tech" method of choice for parathyroid gland localization.