Magnitude of parathyroid hormone elevation in primary hyperparathyroidism: Does time of day matter?

BackgroundParathyroid hormone demonstrates a circadian rhythm in nondiseased patients, but it is unclear if this diurnal variation persists in the context of primary hyperparathyroidism. We anecdotally noticed that parathyroid hormone levels drawn early on the morning of parathyroid surgery (preincision parathyroid hormone), were of lower magnitude than values obtained at later times in the day. If present, a time-of-day based variation in parathyroid hormone could have important clinical implications on intraoperative surgical decision making.MethodsWe performed an Institutional Review Board-approved, retrospective chart review of patients undergoing parathyroidectomy for primary hyperparathyroidism between October 2019 and February 2022 at a quaternary care referral center. Demographic, laboratory, imaging, and operative parameters were extracted. Analysis was performed using mixed models for repeated measures with a first order autoregression correlation structure. Parathyroid hormone values were compared before and after hourly intervals between 6:00 A.M. and 12:00 P.M.ResultsOf 418 patients, the mean age was 61 years old, 80% of patients were female, and two-thirds had single-gland disease. A total of 933 parathyroid hormone levels were included in the analysis and median parathyroid hormone was 97.3 pg/mL. Parathyroid hormone levels were noted to be significantly lower if they were drawn before 7:00 A.M. This diurnal variation persisted in patients with single-gland and advanced hyperparathyroidism but was abrogated in multi-gland and low-baseline-parathyroid hormone disease.ConclusionIn patients with primary hyperparathyroidism, parathyroid hormone levels were significantly lower in the early morning hours, especially in patients with single-gland and high-baseline-parathyroid hormone hyperparathyroidism. This may have implications for intraoperative decision making when utilizing an early morning, preincision parathyroid hormone value.     

The differentiation of primary hyperparathyroidism from the hypercalcemia of malignancy.

The presence of hypercalcemia in patients with known cancers may be due to the cancers themselves, or to co-existing primary hyperparathyroidism. The differentiation of primary hyperparathyroidism from the hypercalcemia of malignancy is important since the relief of distressing symptoms and prevention of hypercalcemic crises and renal failure can be accomplished relatively easily by parathyroid surgery in the former condition, and only with difficulty, at times, with fluids and drugs in the latter condition. The histories of three recent patients are presented, which demonstrate the difficulties inherent in the differentiation of these conditions. These patients were ultimately found at operation to have primary hyperparathyroidism in addition to malignancies of the cervix, adrenal gland and kidney. In our experience the following have been helpful in establishing a diagnosis; history of hypercalcemia prior to development of cancer, the type of cancer itself, the effect of cancer therapy on the hypercalcemia, and selective venous sampling with radioimmunoassay for parathyroid hormone.     

Localization diagnosis of epithelial-body tumors through selective determination of parathyroid hormone. Surgical sequelae of a new method]

A new method for the localisation of abnormal parathyroid tissue is reported. This is carried out by selective venous blood sampling from the thyroid veins and the large veins of the neck. Parathyroid hormone levels are measured by radioimmunoassay. The peak hormone level indicates the site of the tumor suspected. Parathyroid venous blood was taken in 15 patients with primary hyperparathyroidism. In 12 patients localisation of the parathyroid tumor was achieved pre-operatively. The procedure is especially valuable in patients with previous unsuccessful parathyroid surgery. There are no complications or contraindications to the method.     

Hypercalcemia with a parathyroid hormone level of ≤50 pg/mL: Is this primary hyperparathyroidism?

BackgroundPrimary hyperparathyroidism is characterized by hypercalcemia with inappropriately normal or elevated parathyroid hormone. However, the absolute parathyroid hormone value that is defined as inappropriately normal is unclear. We reviewed our experience with parathyroidectomy in patients with hypercalcemia and parathyroid hormone of ≤50.0 pg/mL (normal range 12.0–88.0 pg/mL).MethodsA total of 2,349 patients underwent parathyroidectomy for primary hyperparathyroidism between 2000 and 2021. Of these, 149 patients had preoperative parathyroid hormone ≤50.0 pg/mL (parathyroid hormone ≤50). The biology and outcomes were compared to patients with parathyroid hormone >50.0 pg/mL (parathyroid hormone >50).ResultsOf the parathyroid hormone ≤50 patients, the median parathyroid hormone was 40.0 pg/mL (range 11.6–50.0 pg/mL). All patients were found to have abnormal hypercellular parathyroid glands with a cure rate of 96.7%. When compared to the parathyroid hormone >50 group, the parathyroid hormone ≤50 group was younger (56 ± 15 vs 60 ± 14 years, P < .001) with a lower body mass index (28.7 ± 7.0 kg/m² vs 31.2 ± 7.9 kg/m², P < .001), higher rate of fatigue (73.2% vs 63.0%, P = .033), and higher rate of multiglandular disease (58.9% vs 31.9%, P < .001). There was no difference between the groups with respect to patient demographics, rate of previous parathyroidectomy, surgical cure, or postoperative complications (persistent or recurrent hyperparathyroidism and hypocalcemia).ConclusionPatients with hypercalcemia and parathyroid hormone ≤50 pg/mL have a similar clinical presentation and rate of surgical cure to other primary hyperparathyroidism patients and should be considered for parathyroidectomy. Most of these patients have multiglandular disease and thus should be considered for bilateral parathyroid exploration.     

Incidence of recurrence in long-term follow-up of 100 patients after surgery for primary hyperparathyroidism]

The percentages for recurrence or persistence of hyperparathyroidism after operation for pHPT vary between 3 and 7% according to the pertinent literature. These groups of authors have a broad experience based on a large number of patients treated. At our institute we have operated for pHPT an average of 5 patients per year. Given our limited experience we reexamined 100 consecutive patients which were operated for pHPT between 1968 and 1988 in order to determine our own rate of recurrence. The rate for persistent or recurrent hyperparathyroidism was at 8% slightly higher than in the literature reviewed. When reexamining the patients we took the history concerning the preoperative symptomatology and its postoperative course. Furthermore we compared a radioimmunoassay measuring the midmolecule region of the parathyroid hormone with a immunochemiluminometric assay determining the intact and biologically active hormone regarding sensitivity and specificity. The results are presented and compared with the literature reviewed.     

Hyperparathyroidism, cirrhosis, and portacaval shunt. A new clinical syndrome

This is a report of six patients with cirrhosis of the liver in whom primary hyperparathyroidism occurred due to a solitary parathyroid adenoma 3 months to 9 years after undergoing emergency portacaval shunt for hemorrhage from esophageal varices. The presenting symptoms in all six patients were weakness and bone pain. Three patients had a bone fracture after insignificant trauma, one and probably two passed kidney stones, and a duodenal ulcer developed in two. Bone x-ray films showed generalized osteoporosis in all patients. Renal function and arterial blood pH were within normal limits in every patient. The diagnosis of primary hyperparathyroidism in each patient was based on repeated demonstrations of hypercalcemia, hypophosphatemia, and markedly elevated serum immunoreactive parathyroid hormone concentrations. In all six patients, removal of the parathyroid adenoma resulted in disappearance of symptoms; normalization of serum calcium, phosphorus, and immunoreactive parathyroid hormone levels; and in four of the six, improvement in radiographic evidence of osteoporosis during follow-up of from 1 to 6 years. The association of cirrhosis, portacaval shunt, and primary hyperparathyroidism has not been documented previously. Our six patients with primary hyperparathyroidism constitute 3.4 percent of 174 survivors of emergency portacaval shunt in a series of 264 unselected, consecutive patients with cirrhosis and bleeding esophageal varices. Hepatic osteodystrophy is known to have occurred in only 11 of these 174 survivors. Primary hyperparathyroidism may be a more common cause of hepatic osteodystrophy than has been previously recognized, and should be considered in patients with cirrhosis in whom weakness, bone pain, and bone demineralization develop, particularly if they have a portacaval anastomosis.     

Unilateral versus bilateral neck exploration for primary hyperparathyroidism: a prospective randomized controlled trial

OBJECTIVE: To compare unilateral and bilateral neck exploration for primary hyperparathyroidism in a prospective randomized controlled trial. SUMMARY BACKGROUND DATA: Based on the assumption that unilateral neck exploration for a solitary parathyroid adenoma should reduce operating time and morbidity, a variety of minimally invasive procedures have challenged the idea that bilateral neck exploration is the gold standard for the surgical treatment of primary hyperparathyroidism. However, to date, no open prospective randomized trial has been published comparing unilateral and bilateral neck exploration. METHODS: Ninety-one patients with the preoperative diagnosis of primary hyperparathyroidism were randomized to unilateral or bilateral neck exploration. Preoperative scintigraphy and intraoperative parathyroid hormone measurement guided the unilateral exploration. Gross morphology and frozen section determined the extent of parathyroid tissue resection in the bilateral group. The primary end-point was the use of postoperative medication for hypocalcemic symptoms. RESULTS: Eighty-eight patients (97%) were cured. Histology and cure rate did not differ between the two groups. Patients in the bilateral group consumed more oral calcium, had lower serum calcium values on postoperative days 1 to 4, and had a higher incidence of early severe symptomatic hypocalcemia compared with patients in the unilateral group. In addition, for patients undergoing surgery for a solitary parathyroid adenoma, unilateral exploration was associated with a shorter operative time. The cost for the two procedures did not differ. CONCLUSIONS: Patients undergoing a unilateral procedure had a lower incidence of biochemical and severe symptomatic hypocalcemia in the early postoperative period compared with patients undergoing bilateral exploration. Unilateral neck exploration with intraoperative parathyroid hormone assessment is a valid surgical strategy in patients with primary hyperparathyroidism with distinct advantages, especially for patients with solitary parathyroid adenoma.     

Calcimimetic agents and the calcium-sensing receptor

Blood ionized extracellular calcium is closely regulated. To accomplish this, a hormone-like receptor that is responsive to extracellular ionized calcium regulates both the secretion of parathyroid hormone and the excretion of urinary calcium (as well as other cellular processes). Several hereditary disorders have mutations that cause either loss or gain of function of the calcium-sensing receptor, and alterations of the calcium-sensing receptor may play a role in both primary and secondary hyperparathyroidism. Calcimimetics are agents that act to make the calcium-sensing receptor more sensitive to extracellular ionized calcium; thereby they suppress the secretion of parathyroid hormone. Early trials in animal models of secondary hyperparathyroidism and in patients with primary hyperparathyroidism or with uremic secondary hyperparathyroidism have shown that the first generation calcimimetic, R-568, effectively lowers parathyroid hormone levels and is well tolerated.     

The utility of a rapid parathyroid assay for uniglandular, multiglandular, and recurrent parathyroid disease

The rapid parathyroid hormone assay (rPTH) is an effective tool in minimally invasive resections of parathyroid adenomas. However, there are relatively few reports examining its utility in the full spectrum of parathyroid disease. The purpose of this study was to examine the utility of the rapid parathyroid hormone assay in uniglandular, multiglandular, and recurrent hyperparathyroidism. A retrospective analysis of all patients undergoing parathyroid resection from June 2001 to March 2003 was undertaken. All patients underwent preoperative localization studies. Rapid parathyroid hormone (PTH) levels were drawn immediately prior to and 10 minutes following parathyroid resection. A decline of > or = 50 per cent rPTH qualified as a successful/complete resection. Additional intraoperative samples were drawn as needed for patients with multiglandular disease. Of 46 treated patients who were examined (average age, 54 years), 30 had single, 12 patients had multigland disease, and 4 had recurrent/persistent hyperparathyroidism. Thirty-seven patients had primary hyperparathyroidism (32 with single and 3 with double adenomas; 2 with hyperplasia), 4 patients had secondary hyperparathyroidism, and 5 tertiary hyperparathyroidism. All procedures were considered successful, as every patient exhibited a postresection decrement in rPTH exceeding 50 per cent (average decrement, 91%). Although 2 patients exhibited a postoperative PTH increase exceeding 50 per cent of the preoperative value, all remained asymptomatic and eucalcemic (median follow-up, 21.5 months). The rPTH assay is an effective tool in determining success of parathyroidectomy in patients with primary uni- and multiglandular as well as recurrent hyperparathyroidism. It can be used to achieve minimally invasive neck dissections or guide surgical decision-making in more complex cases.     

Primary hyperparathyroidism: four- to eight-year postoperative follow-up demonstrating persistent functional insignificance of microscopic parathyroid hyperplasia and decreased autonomy of parathyroid hormone release.

Thirty-nine patients with primary hyperparathyroidism were studied four to eight years after their initial operation. In six patients, both the pathologist and surgeon agreed on the diagnosis of solitary adenoma; in 16 patients, the surgeon diagnosed solitary adenoma and the pathologist parathyroid hyperplasia (microscopic hyperplasia). In 16 patients, primary chief cell hyperplasia was agreed upon by the pathologist and surgeon. In the 16 patients with microscopic hyperplasia, there have been no long-term recurrences of hypercalcemia, but, in two patients, plasma parathyroid hormone levels are high. Parathyroid hormone--total calcium regression curves demonstrate significant preoperative correlation in solitary adenoma, p less than 0.01, and primary chief cell hyperplasia, p less than 0.05. After operation, significant correlations were not found between parathyroid hormone and total calcium. T-testing slope differences of pre- and postoperative parathyroid hormone--total calcium regression curves demonstrates a significant (p less than 0.01) shift to the right of the microscopic hyperplasia patients after operation, moving them to a broader range of total calcium per picogram parathyroid hormone. We conclude that 1) in primary hyperparathyroidism, positive regulation of total calcium by autonomously released parathyroid hormone exists in patients with solitary adenoma and chief cell hyperplasia; 2) autonomously functioning parathyroid tissue has been removed by operation for solitary adenoma with coexistent microscopic parathyroid hyperplasia. In this four- to eight-year follow-up period, it is clear that microscopic parathyroid hyperplasia is not associated with recurrent hypercalcemia. Two functionally distinct forms of parathyroid suppression are suggested; positively regulated microscopic hyperplasia and negatively regulated pathologically suppressed glands.     

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.     

Incidence and prognosis of parathyroid gland carcinoma: a population-based study in The Netherlands estimating the preoperative diagnosis

Background

Parathyroid carcinoma is a rare malignancy and generally is diagnosed after surgery for primary hyperparathyroidism. Lack of a preoperative diagnosis and ill-considered surgical planning with its impact on survival are ill-described.

Methods

In a retrospective population-based cohort study the clinical features, treatment, recurrences, and survival of 41 parathyroid cancer patients are reported and compared with characteristics of patients with primary hyperparathyroidism.

Results

Patients with parathyroid carcinoma had significantly higher serum parathyroid hormone and calcium levels compared with patients with primary hyperparathyroidism. Nineteen patients (46%) had a palpable neck mass. A parathyroid hormone level more than 3 times the upper normal limits was suspicious and levels more than 10 times carried a positive predictive value of 84% for carcinoma. Ten-year recurrence-free and disease-specific survival rates were 71% and 79%, respectively.

Conclusions

Parathyroid hormone levels of more than 3 times upper normal limits, palpable neck mass, and profound hypercalcemia are suspicious signs of carcinoma necessitating surgical exploration by an experienced surgeon.     

Parathyroidectomy in chronic renal failure

Parathyroidectomy was carried out in 26 patients over a 14-year period. Excellent results were obtained in patients with severe hyperparathyroidism. Vascular calcification, hypercalcaemia and pruritus did not justify surgery unless associated with unequivocal hyperparathyroidism. 13 patients required intravenous calcium infusion for up to 2 weeks to control post-operative hypocalcaemia. Calcium requirements could be predicted from the pre-operative plasma alkaline phosphatase level. Following operation continued treatment with vitamin D was necessary to prevent hypocalcaemia. Hyperparathyroidism recurred in 1 patient after 8 years and 4 patients developed osteomalacia. Since parathyroid hormone may have toxic effects other than those on bone, maintenance of normal levels should be a long-term objective in the treatment of patients with chronic renal failure. Where large parathyroid glands are present, surgical reduction in gland mass is a logical prelude to long-term suppression of parathyroid hormone with vitamin D and phosphate-binding agents.     

A difficult case of mediastinal parathyroid adenoma: theoretical and clinical considerations

About one quarter of patients with primary hyperparathyroidism have ectopic parathyroid tissue. The majority of parathyroid glands can be reached through a cervical approach, but in about 2% of the cases the ectopic gland is in the mediastinum in a location that requires a thoracic approach. Failure to remove ectopic mediastinal parathyroid tissue results in persistent hyperparathyroidism. Reoperative exploration for persistent hyperparathyroidism is often difficult even in the hands of experienced surgeons. Recent advances in preoperative localization techniques and intraoperative parathyroid hormone measurement have improved the rates of successful resection. We present a difficult case of persistent hyperparathyroidism secondary to an ectopic middle mediastinal parathyroid adenoma, which was eventually successfully managed in a specialised unit.     

Early biochemical response to parathyroidectomy for primary hyperparathyroidism and its predictive value for recurrent hypercalcemia and recurrent primary hyperparathyroidism

BackgroundThe traditional definition of cure after parathyroidectomy (PTX) for primary hyperparathyroidism is normocalcemia. Our hypothesis was that early postoperative levels of serum calcium and parathyroid hormone after PTX would have predictive value for later recurrence.MethodsWe performed a retrospective study of 1,146 patients with primary hyperparathyroidism who underwent PTX and had long-term biochemical follow-up. The first postoperative serum level of calcium and parathyroid hormone values were used to categorize patients into the following four early biochemical response groups: (1) complete response (normal calcium and normal parathyroid hormone), (2) partial response with hyperparathormonemia (normal calcium and increased parathyroid hormone), (3) partial response with hypercalcemia (increased calcium and normal parathyroid hormone), and (4) non-response (increases in both calcium and parathyroid hormone). Incidences of recurrent hypercalcemia and recurrent primary hyperparathyroidism >6 months after operation were then analyzed.ResultsThe overall rate of any elevated serum levels of calcium and any increase in serum levels of parathyroid hormone during >6-month follow-up was 9.8% (112 of 1146), with 6.6% (57 of 861) for group 1, 27% (35 of 129) for group 2, and 16% (20 of 127) for group 3 (P < .02). Partial biochemical responses with either increased serum calcium or increased parathyroid hormone levels were the strongest predictors of any episode of increased serum levels of calcium after 6 months and was associated with 2.7× to 4.3× the risk of recurrent primary hyperparathyroidism, respectively.ConclusionThis study demonstrates the importance of measuring parathyroid hormone in the early postoperative period to better predict later recurrent primary hyperparathyroidism.     

Parathyroid Adenomas versus Four-gland Hyperplasia as the Cause of Primary Hyperparathyroidism in Patients with Prolonged Lithium Therapy

Chronic lithium therapy in patients with affective psychiatric disorders has been implicated as the cause of hypercalcemia and primary hyperparathyroidism. Our objective was to evaluate whether primary hyperparathyroidism was caused by an adenoma or four-gland hyperplasia. The medical records of 15 patients with affective psychiatric disorders who were treated with chronic lithium therapy from 1982 to 1997, all of whom were operated on for primary hyperparathyroidism, were reviewed. Data on age, symptoms, duration of lithium therapy, pre- and postoperative calcium levels, and parathyroid hormone levels were collected. Parathyroid histology for each patient was independently and blindly reviewed. The mean age was 58 +/- 10 years, the mean duration of lithium therapy 10.7 +/- 6 years, and the mean preoperative calcium level 11.7 +/- 0.5 mg/dl. All patients underwent bilateral neck exploration with selective resection of enlarged glands. Of the 15 patients, 14 (92%) had adenomas (11 single, 3 double), and 1 (8%) had four-gland hyperplasia. All patients were rendered eucalcemic, with a postoperative calcium level of 9.2 +/- 0.5 mg/dl ( p < 0.005). All patients resumed their lithium therapy, with 1 of 15 patients developing recurrent hyperparathyroidism 2 years following the first operation; this patient required reexploration, at which time an adenoma was resected. In our experience hyperparathyroidism in patients who have undergone prolonged therapy with lithium is associated with a high incidence of parathyroid adenomas versus four-gland hyperplasia. This suggests that lithium selectively stimulates growth of parathyroid adenomas in susceptible patients, who are best treated with adenoma excision rather than subtotal parathyroidectomy.     

Calcimimetic agents for the treatment of hyperparathyroidism

Calcimimetic agents are small organic molecules that act as allosteric activators of the calcium sensing receptor. They lower the threshold for receptor activation by extracellular calcium ions and, in parathyroid cells, diminish parathyroid hormone secretion. Calcimimetic compounds represent a novel class of therapeutic agents that may provide a way of controlling excess parathyroid hormone secretion in several clinical disorders. Although experience from clinical trials in humans is limited, available data suggest that calcimimetic agents effectively lower plasma parathyroid hormone levels in patients with primary hyperparathyroidism and those with secondary hyperparathyroidism caused by end-stage renal disease. Calcimimetic compounds thus have considerable potential as a new approach to the medical management of several important clinical disorders of bone and mineral metabolism.     

Function in athymic nude mice of parathyroid heterografts from patients with primary hyperparathyroidism and secondary hyperparathyroidism

Heterotransplantation of adenomatous parathyroid glandular tissue from humans with primary hyperparathyroidism into athymic nude mice creates a unique animal model of this disease. The mice manifest high concentrations of both midregion/C-terminal human parathyroid hormone and biologically active intact human parathyroid hormone relative to either mice with no implants or mice that received normal human parathyroid tissue. Secretion of these substances is maintained in most mice for at least 9 to 13 months after implantation. In addition, animals that have experienced implantation exhibit other characteristics associated with human primary hyperparathyroidism including relative hypercalcemia and increased renal 25-hydroxyvitamin D-1 alpha-hydroxylase activity. We also measured these parameters in a group of nude mice that received transplantation of a similar mass of hyperplastic parathyroid tissue that was obtained from patients with uremic secondary hyperparathyroidism. Although we hypothesized that the level of human parathyroid hormone secretion from these implants would fall over time in response to the normal host environment, hormone levels remained as high as those in recipients of adenomatous heterografts, even after 9 to 13 months. Moreover, similar biologic effect of the excess parathyroid hormone (i.e., relative hypercalcemia, hyperphosphatasemia, and increased 1,25-dihydroxyvitamin D biosynthesis) were detected. These animal models should prove extremely useful in supplementing our understanding of hyperparathyroid disorder in man.     

Pre-operative localization of parathyroid tissue by selective neck vein catheterization and radioimmunoassay of parathyroid hormone.

Preoperative localization of parathyroid tissue by selective neck vein catheterization and radiommunoassay of parathyroid hormone (PTH) was used in 18 patients with primary hyperparathyroidism (PHPT), 9 or whom had earlier been subjected to surgical neck exploration. Sampling from large and small neck veins provided localizing data in 11 of 15 patients with parathyroid adenomas. In 3 other patients, diffuse parathyroid hyperplasia was also correctly predicted preoperatively. In 3 patients hyperplasia was found, the surgical procedure was not influenced in a negative way by the failures. Large vein sampling was less helpful then selective small vein sampling. The results show that selective venous sampling from the neck and radioimmunoassay of PTH are valuable preoperative adjuncts to surgical exploration, escpecially in patients who have had previous neck surgery. Since the catheterization procedure is uncomfortable to the patient and difficult for the investigator, its use should be restricted to patients with previous neck surgery, Neck vein catheterization can probably not be used to establish the diagnosis of PHPT in uncertain cases.     

The role of intraoperative parathyroid hormone assay in the surgical management of hyperparathyroidism

Surgical management of primary hyperparathyroidism has undergone several chances in recent years and historically has required bilateral neck exploration with identification of the parathyroid adenoma together with three normal glands. The intraoperative hormone assay allows a more limited procedure by confirming complete removal of hypersecreting tissue. The Authors report surgical treatment of 24 consecutive hyperparathyroidism and conclude that evaluation of intraoperative hormone assay accurately predicts the determination of adequacy of resection and the correct outcome of surgery in patients with parathyroid adenomas.