Recovery of parathyroid hormone secretion after parathyroid adenomectomy

Persistent Elevation of Parathormone Levels after Surgery for Primary Hyperparathyroidism

BACKGROUND

Persistent elevation of serum parathyroid hormone (PTH) despite normocalcemia have been documented in 8- 40% of patients after parathyroidectomy. We hereby report our experience from different centers across India to determine clinical significance of postoperatively elevated PTH levels and review relevant literature.

METHODS

We conducted a retrospective case series study and reviewed all the patients who underwent surgery for primary hyperparathyroidism (PHPT) from April 2010 to January 2020.

RESULTS

Total of 201 patients was diagnosed as PHPT. Out of available follow-up data of 180 patients, a total of 54 patients (30%) had persistently elevated PTH (PePTH) at 1 month. Patients with PePTH were older with higher preoperative serum calcium, iPTH, alkaline phosphatase and lower serum phosphate and 25-hydroxy vitamin D3 levels. Creatinine clearance was found to be significantly lower in patients with PePTH. Multiple linear regression analysis revealed that preoperative 25-OH D3 concentration, creatinine clearance and iPTH are the factors influencing persistent elevation of PTH levels. Significantly lower serum calcium and higher alkaline phosphatase levels were observed in PePTH patients with preoperative 25-OH D3 levels <20 ng/mL. Thirty patients at 6 months, 24 patients at 1 year, 18 patients at 2 years and 9 patients at 3 years had eucalcemic PTH elevation. Nine out of 126 (7%) patients with normal initial postoperative calcium and iPTH levels developed PePTH, with none culminating into recurrent hyperparathyroidism.

CONCLUSION

Though the pathogenesis of such a phenomenon still remains to be elucidated, a multifactorial mechanism appears to play a role.

Intraoperative Parathyroid Hormone Monitoring in Guiding Adequate Parathyroidectomy

BACKGROUND

Parathyroidectomy has been traditionally performed through bilateral neck exploration (BNE). However, with the use of intraoperative parathyroid hormone (IOPTH) assay along with preoperative localization studies, focused parathyroidectomy can be performed with good surgical success rate, multiglandular disease can be predicted, and hence recurrence and surgical failure can be prevented. Furthermore, it predicts eucalcemia in the postoperative period. The aim of this study was to evaluate the usefulness of IOPTH assay in guiding adequate parathyroidectomy in patients of primary hyperparathyroidism.

MATERIALS AND METHODS

Between year 2015 and 2017, 45 patients of primary hyperparathyroidism underwent parathyroidectomy with IOPTH assay employed as an intraoperative tool to guide the surgical procedure. Blood samples were collected: (1) at preincision time, (2) preexcision of gland, (3) 5-min postexcision of gland, and (4) 10-min postexcision of gland. On the basis of the Irvin criterion, an intraoperative PTH drop >50% from the highest either preincision or preexcision level after parathyroid excision was considered a surgical success. Otherwise, BNE was performed and search for other parathyroid glands done.

RESULTS

Ten-min postexcision PTH levels dropped >50% in 34 (75.6%) patients. True positive among them were 31 (68.8%), true negative 8 (17.7%), false positive 3 (6.6%), and false negative 3 (6.6%). We performed focused exploration at the outset in 40 (88.9%) patients and bilateral exploration for five patients as guided by preoperative localizing studies. Hence, IOPTH was helpful in guiding further exploration in 8 (17.7%) patients and prevented further exploration in 32 (71.1%) patients and also was able to predict eucalcemia in 97.7% patients at 6 months. Thus, IOPTH was able to obviate or to ask for additional procedure in 88.8% of patients. However, in three (6.6%) patients, IOPTH would guide unnecessary exploration and in equally, that is, three (6.6%) patients may require reoperation for unidentified parathyroids.

CONCLUSION

IOPTH in adjunct with other localizing studies is very helpful for carrying out successful parathyroidectomy in uniglandular disease and predicting postoperative eucalcemia. However, more importantly, its role is valuable in equivocal imaging, in such cases, it prevents unnecessary exploration or helps in adequate parathyroidectomy.

Intraoperative Fall in Plasma Levels of Intact Parathyroid Hormone in Patients Undergoing Parathyroid Adenomectomy

Intraoperative measurement of intact parathyroid hormone (PTH) can be used to evaluate the success of parathyroid surgery in primary hyperparathyroidism associated with parathyroid adenoma. To evaluate this approach we used a modified immunoradiometric assay (IRMA) to study the kinetic patterns of circulating PTH disappearance in 13 patients undergoing adenomectomy for single adenoma. The rapid and the standard assay for PTH measurement in plasma were used and compared. The two methods showed a highly significant correlation (r=0.995; p<0.0001).

We reported a decrease in PTH to 18.2±2.30 (mean±SEM) from baseline values at 15 minutes after successful parathyroid adenomectomy in the 13 patients. The biphasic pattern of serum PTH clearance was calculated in 8 of the studied patients with a fast phase showing a half-life (T1/2) of 3.99 (SEM 0.464) minutes and a slow phase with a T1/2 of 91.0 (SEM 33.6) minutes. Half the amount of the basal values was reached between 4 and 9 minutes.

Our study concludes that the modified IRMA for intraoperative measurement is feasible, reliable and sufficiently precise for low hormone values. Since it may yield information on the half-life of PTH in the circulation, it may play a role in the surgical guidance for total exeresis of hyperfunctioning tissue

Primary hyperparathyroidism due to an intrathyroidal parathyroid adenoma associated with chronic lymphocytic thyroiditis

This is a case of a 44-year-old woman with an anterior neck mass and hypothyroidism who presented with an incidental finding of an elevated serum calcium level and was found to have primary hyperparathyroidism and osteoporosis. During surgical exploration no parathyroid adenoma was found, although a nodule was palpated within the right thyroid lobe. Examination of the excised right thyroid lobe revealed an intrathyroidal parathyroid adenoma and chronic lymphocytic thyroiditis. After surgery, she did not develop severe hypocalcaemia and this was attributed to preoperative treatment with pamidronate. In the months following surgery, parathyroid hormone remained undetectable.

A 10-year experience in intraoperative parathyroid hormone measurements for primary hyperparathyroidism: a prospective study of 91 previous unexplored patients

Introduction. Primary hyperparathyroidism (PHP) is characteristically determined by high levels of calcium and high or inappropriate levels of parathyroid hormone (PTH). Technological advances have dramatically changed the surgical technique over the years once intraoperative parathyroid hormone (IOPTH) assay had allowed for focused approaches. Objective. To evaluate our 10-year experience in employing a rapid intraoperative PTH assay for PHP. Methods. A prospective cohort of 91 PHP-operated patients in a tertiary institution in São Paulo, Brazil, from June 2000 to April 2011. Results. We had 85 (93.4%) successful parathyroidectomies, 6 (6.6%) failed parathyroidectomies in 91 previous unexplored patients, and 5 (100%) successful remedial surgeries. The IOPTH was true-positive in 88.5%, true-negative in 7.3%, false-positive in 2.1%, and false-negative in 2.1% of the procedures. IOPTH was able to obviate additional exploration or to ask for additional exploration in 92 (95.8%) procedures. Conclusion. The IOPTH revealed to be an important technological adjunct in the current parathyroid surgery for PHP.

Pre-operative serum alkaline phosphatase as a predictor for hypocalcemia post-parathyroid adenectomy

BACKGROUND

Post-operative hypocalcemia (POH) may complicate parathyroidectomy for primary hyperparathyroidism. This study investigates the relationship between POH and pre-operative risk factors to identify a simple method to predict POH risk.

METHODS

Retrospective data on risk factors for 29 patients was collected for age, pre-operative serum calcium, alkaline phosphatase (ALP), parathyroid hormone (PTH), adenoma size, gender, and bisphosphonate pre-treatment. These were screened to exclude those with small effect sizes, and analyzed using Univariate General Linear Modeling (GLM) with trough serum calcium (TSC) as the dependent variable. The regression function of the significant variables against TSC was plotted with 95% CI fit lines. The cut-off regression value was read from the lower fit line for the threshold TSC of 2.0 mmol/L.

RESULTS

After screening, log-transformed age (r=0.600), ALP (r=-0.415), and PTH (r=-0.433) were entered into GLM analysis, which showed that only ALP was significant (p=0.016 Eta-squared=0.220). The GLM model had a partial Eta-squared of 0.559 with 98% observed power. The plot of TSC against log-ALP gave an ALP cut-off of 340 U/L.

CONCLUSIONS

The study shows that there is a strong relationship between ALP and TSC, and that patients with a pre-operative ALP less than 340 U/L are unlikely to have symptomatic POH (100% sensitivity, 95% specificity). While vitamin D was not analyzed in this study, the ALP cut-off is conservative and should still screen out cases with severe vitamin D deficiency. We therefore recommend that pre-operative ALP be utilized to complement clinical protocols for POH management in parathyroid adenomectomy patients.

Reliable early prediction for different types of post-thyroidectomy hypocalcemia

Objectives

High incidence of hypocalcemia after thyroidectomy is a major determinant in delay of discharge. Even though many studies have focused on the search for reliable early predictors of postoperative hypocalcemia, definitions of hypocalcemia are diverse; therefore, interpretation and application of previously reported findings may not be easy. We aimed to elucidate diverse patterns of post-thyroidectomy hypocalcemia and to provide reliable early predictors for these different types of hypocalcemia.

Methods

Retrospective chart review was performed and eligible 112 patients of thyroidectomy were categorized into four groups according to symptomatic and/or biochemical hypocalcemic criteria. A mismatch of occurrence and the timing of symptomatic or biochemical abnormalities were evaluated. Predictive values of commonly used biomarkers were compared in each group; levels of serum total calcium and ionized calcium, and intact parathyroid hormone (PTH).

Results

Among 62 hypocalcemic patients, 45 patients (72.5%) experienced both symptomatic and biochemical abnormalities during hospitalization. A mismatch on the timing of initial detection of symptomatic and biochemical hypocalcemia was observed in 21 patients (46.6%). Intact PTH level measured at 1 hour was a useful indicator in prediction of symptomatic hypocalcemia with 79.7-87.4% of diagnostic accuracy. Serum ionized calcium measured next morning after surgery was a reliable predictor of biochemical hypocalcemia with 77.9-94.8% of diagnostic accuracy.

Conclusion

For the safety of patients, the possibility of both symptomatic and biochemical hypocalcemia should be considered together before deciding early discharge. Using intact PTH for symptomatic hypocalcemia and day-1 ionized serum calcium level for biochemical hypocalcemia will be helpful for the reliable prediction of heterogeneous nature of postoperative hypocalcemia.

Bone mineral density analysis in patients with primary hyperparathyroidism associated with multiple endocrine neoplasia type 1 after total parathyroidectomy

OBJECTIVE

Limited data have been reported on the effect of parathyroidectomy (PTx) on bone mineral density (BMD) in the setting of patients with hyperparathyroidism (HPT) associated with multiple endocrine neoplasia type 1 (MEN1). This study investigates the impact of total PTx on BMD in patients with HPT/MEN1.

DESIGN AND PATIENTS

A case series study was performed in a tertiary academic hospital. A total of 16 HPT/MEN1 patients from six families harbouring MEN1 germline mutations were subjected to total PTx followed by parathyroid auto-implant in the forearm.

MEASUREMENTS

Bone mineral density values were assessed using dual-energy X-ray absorptiometry.

RESULTS

Before PTx, reduced BMD (Z-score <-2.0) was highly prevalent in the proximal one-third of the distal radius (1/3 DR) (50%), lumbar spine (LS) (43.7%), ultradistal radius (UDR) (43.7%), femoral neck (FN) (25%) and total femur (TF) (18.7%) in the patients. Fifteen months after PTx, we observed a BMD improvement in the LS (from 0.843 to 0.909 g/cm(2); +8.4%, P = 0.001), FN (from 0.745 to 0.798 g/cm(2); +7.7%, P = 0.0001) and TF (from 0.818 to 0.874 g/cm(2); +6.9%, P < 0.0001). No significant change was noticed in the 1/3 DR and UDR after PTx.

CONCLUSIONS

This data confirmed BMD recovery in the LS and FN after PTx in HPT/MEN1 patients. We also documented a significant BMD increase in the TF and no change in both the 1/3 DR and UDR BMD after PTx. Our data suggest that LS and proximal femur are the most informative sites to evaluate the short-term BMD outcome after PTx in HPT/MEN1 subjects.

Utilidade da medida de PTH intra-operatório no tratamento cirúrgico do hiperparatiroidismo primário e secundário: análise de 109 casos

INTRODUÇÃO: A medida de PTH intra-operatório (PTH-IO) foi inicialmente descrita em 1988, sendo potencialmente útil na definição de sucesso após a paratiroidectomia. OBJETIVOS: Avaliar prospectivamente perfil de decaimento do PTH-IO e sua capacidade de prever sucesso cirúrgico no hiperparatiroidismo primário (HPP) e secundário à insuficiência renal (HPS). PACIENTES E MÉTODOS: 109 pacientes operados entre 06/2000 e 12/2004, sendo 33 HPP, 76 HPS (52 em diálise, 24 transplantados renais). PTH-IO: método imunométrico rápido (Elecsys-PTH/Immunoassay-Roche); tempo para resultado: 10 minutos. Coletas de sangue periférico nos tempos basal, 10 e 20 minutos pós-paratiroidectomia. RESULTADOS: HPP: queda média de PTH de 79,2% aos 10 minutos. HPS: queda média de PTH de 85,8% e 87,6% aos 10 minutos nos pacientes diálise e transplantados respectivamente. A cirurgia foi bem sucedida em todos, exceto em 2 pacientes (1 HPP, 1 HPS). Em ambos não houve queda PTH-IO, sendo constatado adenoma duplo no HPP e paratiróide ectópica no HPS. CONCLUSÃO: Medida PTH-IO fornece resultados confiáveis em tempo rápido, sendo capaz de discriminar persistência da doença se mantidos níveis elevados.

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

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

Reelevation of parathyroid hormone level after parathyroidectomy in patients with primary hyperparathyroidism: importance of decreased renal parathyroid hormone sensitivity

BACKGROUND

We hypothesized that impaired peripheral sensitivity to parathyroid hormone (PTH) may play a role in reelevation of PTH after successful operation for primary hyperparathyroidism (pHPT).

METHODS

Factors affecting reelevation of PTH were determined in 90 patients who underwent parathyroidectomy for pHPT. PTH/nephrogenous cyclic adenosine monophosphate ratio, as an index of renal resistance to PTH, was examined in relation to factors shown to influence reelevation of PTH.

RESULTS

Serum PTH levels were elevated above the upper limit of normal in 23 patients (26%) at 1 week and in 39 patients (43%) at 1 month after parathyroidectomy. These 39 normocalcemic patients with elevated serum PTH at 1 month after parathyroidectomy had a higher preoperative serum level of PTH and lower serum phosphate and 25-hydroxyvitamin D (25OHD) concentrations than those with normal PTH (n = 59). Elevated PTH and low 25OHD were shown by multivariate analysis to be significant predictors of reelevation of PTH. Renal resistance to PTH was higher in patients with vitamin D deficiency or renal insufficiency than in patients with normal serum vitamin D concentrations or normal renal function, and it increased according to increases in levels of PTH.

CONCLUSIONS

The mechanism of PTH reelevation in patients with pHPT after successful parathyroidectomy appears to be renal resistance to PTH.

Measurement of parathyroid hormone and application of parathyroid hormone in intraoperative monitoring

There has been a clear progression in assays for the analysis of PTH and its clinical applications. This includes the innovative use of PTH as a point-of-care assay as an intraoperative measure of the success of parathyroid surgery. The rapid PTH assay has served as a model for the development of other rapid hormone assays, such as for adrenocorticotropic hormone,although the clinical usefulness of these other applications is less well established. Knowledge of the circulating forms of PTH continues to progress. Information about the biologic and immunologic activities of these forms will aid in the interpretation and clinical use of current assays and in the development of new assays with improved specificities. The clinical laboratory will continue to play a vital role in providing testing and support for this important mediator of mineral metabolism.

Rapid intraoperative immunoassay of parathyroid hormone and other hormones: a new paradigm for point-of-care testing

BACKGROUND

The first description of the use of a rapid assay for the measurement of intact parathyroid hormone (PTH) in patients undergoing parathyroidectomy for hyperparathyroidism was reported in 1988. Subsequent improvements in the analytical performance of the rapid intraoperative PTH assay allowed the establishment of its clinical utility in the surgical management of hyperparathyroidism. These modifications also allowed the assay to be performed in or near the operating suite.

METHODS

We searched MEDLINE, using the following key words: intraoperative, rapid, quick, parathyroid hormone, hormone, and immunoassay. Relevant articles that focused on the analytical aspects and clinical utility of rapid intraoperative hormone immunoassays were selected for this review.

CONTENT

On the basis of the positive impact that the rapid intraoperative PTH test has had on both patient outcomes and cost savings, other rapid intraoperative hormone immunoassays for the diagnosis and/or treatment of other endocrine-hormone-secreting tumors have been developed. These hormones share certain characteristics that make them suitable for use as rapid intraoperative tests, i.e., short analyte half-life and/or large analyte concentration gradient, rapid analysis time, and positive clinical utility. Initial studies with cortisol, gastrin, insulin, adrenocorticotropic hormone, and testosterone have shown promising results in preoperative localization studies and/or for assessing the effectiveness of tumor resection during surgery.

CONCLUSION

The emergence of these rapid intraoperative immunoassays indicates that this test format is likely to provide future opportunities to improve patient care by advances in clinical laboratory testing.

Potential Clinical Utility of a New IRMA for Parathyroid Hormone in Postmenopausal Patients with Primary Hyperparathyroidism

Background: A new commercially available (so-called second-generation) IRMA for parathyroid hormone (PTH) separately detects intact PTH and its N-truncated fragments; however, no studies have compared the first- and second-generation IRMAs for PTH in patients with primary hyperparathyroidism (PHPT) to assess their respective diagnostic accuracies.

Methods: We concomitantly investigated 39 postmenopausal patients with PHPT and a control group of 70 healthy postmenopausal women matched for age, renal function, and vitamin D status. In all individuals, PTH was measured with a classic IRMA (PTH-S; DiaSorin Inc.), which uses antibodies directed against epitopes 1–34 and 39–84, and a new method (Scantibodies Laboratory. Inc.), which uses antibodies against epitopes 1–4 and 39–84 (PTH-W) and epitopes 7–34 and 39–84 (PTH-T). We also assayed serum PTH in 10 PHPT patients every 24 h for 5 days after successful surgery.

Results: The different assays gave serum PTH values that were &gt;2 SD higher than values for the control population in 59% (PTH-S), 77% (PTH-W), and 82% (PTH-T) of patients with PHPT. However, ROC curve analysis showed no significant differences among the three PTH assays, demonstrating overlapping diagnostic sensitivities. In PHPT patients, the correlation among the assays was highly significant (r = 0.91–0.92; P &lt;0.001). The ratio PTH-W:PTH-T × 100 showed a gaussian distribution in both PHPT patients and controls, whose mean (SD) values [63.4 (13.3)% vs 64.5 (9.5)%, respectively] did not differ significantly. After parathyroidectomy, the mean percentages of variation in PTH detected with all of the assays were quite similar.

Conclusions: The distribution of the PTH-W:PTH-T ratio in patients and controls suggests that PHPT does not markedly influence the rate at which biologically inactive fragments are generated by central or peripheral cleavage of PTH. The similar postoperative curves seem to contradict the hypothesized effect of acute hypocalcemia in modulating the central secretion of hormonal fragments. Our results indicate that the three investigated assays have similar diagnostic sensitivities in PHPT.

Comparison of parathyroid hormone levels from the intact and whole parathyroid hormone assays after parathyroidectomy for primary and secondary hyperparathyroidism

BACKGROUND

Most commercial intact parathyroid hormone (intact PTH) assays cross-react with non-(1-84) PTH (likely 7-84 PTH). Using a whole-molecule PTH (whole PTH) assay that specifically measured only 1-84 PTH, we compared the kinetics of whole PTH and intact PTH after parathyroidectomy in patients with primary hyperparathyroidism (HPT) and secondary HPT.

METHODS

This study comprised 74 patients with primary HPT caused by a single adenoma and 18 patients with secondary HPT who underwent parathyroidectomy. Blood samples were drawn after anesthesia, just before excision of a single adenoma in primary HPT, and just before excision of the last parathyroid gland in secondary HPT, and at 5, 10, and 15 minutes after excision. The 7-84 PTH level was calculated by subtracting the whole PTH value from the intact PTH value.

RESULTS

There was a difference between the percentage of 7-84 PTH/intact PTH in plasma samples from patients with primary HPT and secondary HPT (28%+/-12% vs 35%+/-9%; P<.05). Plasma whole PTH decreased more rapidly than intact PTH after parathyroidectomy in patients in both the primary HPT (P<.0001) and secondary HPT groups (P<.0001). Decline of intact PTH was slower in patients with secondary HPT than in patients with primary HPT; however, there was no significant difference in the decline of whole PTH between the 2 groups.

CONCLUSIONS

The quick intact PTH assay is not used frequently during surgery in patients with secondary HPT; however, our results suggest that a quick whole PTH assay may be a more useful adjunct to parathyroidectomy in both secondary HPT and primary HPT.

Intraoperative testing for parathyroid hormone: a comprehensive review of the use of the assay and the relevant literature

OBJECTIVE

The rapid intraoperative parathyroid hormone assay is transforming the parathyroidectomy procedure. We present a review of the literature on the use of the assay as an adjunct to surgery. To our knowledge, this is the first review of the literature to encompass and compare all known primary studies of this assay in parathyroidectomy patients.

DATA SOURCES

Articles were collected by searching MEDLINE databases using relevant terminology. The references of these articles were reviewed for additional studies. Supplementary articles pertinent to the parathyroidectomy procedure, preoperative parathyroid localization studies, and intraoperative parathyroid hormone assay development also were examined.

STUDY SELECTION AND DATA EXTRACTION

One hundred sixty-five references were analyzed and categorized separately into groups.

DATA SYNTHESIS

The primary studies of intraoperative data on patients undergoing parathyroidectomy were compared when possible. Studies were analyzed by type of assay used, where performed, turnaround time, and efficiency of use. Reviews of the types of parathyroid surgery and preoperative localization were included for educational purposes.Conclusions.-The intraoperative parathyroid hormone assay is a useful adjunct to preoperative imaging and parathyroid surgery because of its unique ability to detect an occult residuum of hyperfunctioning parathyroid tissue. Use of this assay will obviate the need for frozen section in most routine cases. The test facilitates minimally invasive parathyroidectomy for single parathyroid adenomas, which, in turn, improves cost-effectiveness and cosmetic outcome. Its use in patients with known preoperative multiglandular disease is promising but requires further study.

Usefulness of a rapid immunometric assay for intraoperative parathyroid hormone measurements

Intraoperative parathyroid hormone (IO-PTH) measurements have been proposed to improve operative success rates in primary, secondary and tertiary hyperparathyroidism (PHP, SHP and THP). Thirty-one patients requiring parathyroidectomy were evaluated retrospectively from June 2000 to January 2002. Sixteen had PHP, 7 SHP and 8 THP. Serum samples were taken at times 0 (before resection), 10, 20 and 30 min after resection of each abnormal parathyroid gland. Samples from 28 patients were frozen at -70 C for subsequent tests, whereas samples from three patients were tested while surgery was being performed. IO-PTH was measured using the Elecsys immunochemiluminometric assay (Roche, Mannheim, Germany). The time necessary to perform the assay was 9 min. All samples had a second measurement taken by a conventional immunofluorimetric method. We considered as cured patients who presented normocalcemia in PHP and THP, and normal levels of PTH in SHP one month after surgery and who remained in this condition throughout the follow-up of 1 to 20 months. When rapid PTH assay was compared with a routine immunofluorimetric assay, excellent correlation was observed (r = 0.959, P < 0.0001). IO-PTH measurement showed a rapid average decline of 78.8% in PTH 10 min after adenoma resection in PHP and all patients were cured. SHP patients had an average IO-PTH decrease of 89% 30 min after total parathyroidectomy and cure was observed in 85.7%. THP showed an average IO-PTH decrease of 91.9%, and cure was obtained in 87.5% of patients. IO-PTH can be a useful tool that might improve the rate of successful treatment of PHP, SHP and THP.

Direct effect of acute metabolic and respiratory acidosis on parathyroid hormone secretion in the dog

Because both metabolic (Met Acid) and respiratory acidosis (Resp Acid) have diverse effects on mineral metabolism, it has been difficult to establish whether acidosis directly affects parathyroid hormone (PTH) secretion. Our goal was to determine whether acute Met Acid and Resp Acid directly affected PTH secretion. Three groups of dogs were studied: control, acute Met Acid induced by HCl infusion, and acute Resp Acid induced by hypoventilation. EDTA was infused to prevent acidosis-induced increases in ionized calcium, but more EDTA was needed in Met Acid than in Resp Acid. The PTH response to EDTA-induced hypocalcemia was evaluated also. Magnesium needed to be infused in groups receiving EDTA to prevent hypomagnesemia. The half-life of intact PTH (iPTH) was determined during hypocalcemia when PTH was measured after parathyroidectomy. During normocalcemia, PTH values were greater (p < 0.05) in Met Acid (92 +/- 19 pg/ml) and Resp Acid (77 +/- 22 pg/ml) than in controls (27 +/- 5 pg/ml); the respective pH values were 7.23 +/- 0.01, 7.24 +/- 0.01, and 7.39 +/- 0.02. The maximal PTH response to hypocalcemia was greater (p < 0.05) in Met Acid (443 +/- 54 pg/ml) than in Resp Acid (267 +/- 37 pg/ml) and controls (262 +/- 48 pg/ml). The half-life of PTH was greater (p < 0.05) in Met Acid than in controls, but the PTH secretion rate also was greater (p < 0.05) in Met Acid than in the other two groups. In conclusion, (1) both acute Met Acid and Resp Acid increase PTH secretion when the ionized calcium concentration is normal; (2) acute Met Acid may increase the bone efflux of calcium more than Resp Acid; (3) acute Met Acid acts as a secretogogue for PTH secretion because it enhances the maximal PTH response to hypocalcemia.

Development of a novel immunoradiometric assay exclusively for biologically active whole parathyroid hormone 1-84: implications for improvement of accurate assessment of parathyroid function

We developed a novel immunoradiometric assay (IRMA; whole parathyroid hormone [PTH] IRMA) for PTH, which specifically measures biologically active whole PTH(1-84). The assay is based on a solid phase coated with anti-PTH(39-84) antibody, a tracer of 125I-labeled antibody with a unique specificity to the first N-terminal amino acid of PTH(1-84), and calibrators of diluted synthetic PTH(1-84). In contrast to the Nichols intact PTH IRMA, this new assay does not detect PTH(7-84) fragments and only detects one immunoreactive peak in chromatographically fractionated patient samples. The assay was shown to have an analytical sensitivity of 1.0 pg/ml with a linear measurement range up to 2,300 pg/ml. With this assay, we further identified that the previously described non-(1-84)PTH fragments are aminoterminally truncated with similar hydrophobicity as PTH(7-84), and these PTH fragments are present not only in patients with secondary hyperparathyroidism (2 degrees -HPT) of uremia, but also in patients with primary hyperparathyroidism (1 degrees -HPT) and normal persons. The plasma normal range of the whole PTH(1-84) was 7-36 pg/ml (mean +/- SD: 22.7 +/- 7.2 pg/ml, n = 135), whereas over 93.9% (155/165) of patients with 1 degrees -HPT had whole PTH(1-84) values above the normal cut-off. The percentage of biologically active whole PTH(1-84) (pB%) in the pool of total immunoreactive "intact" PTH is higher in the normal population (median: 67.3%; SD: 15.8%; n = 56) than in uremic patients (median:53.8%; SD: 15.5%; n = 318; p < 0.001), although the whole PTH(1-84) values from uremic patients displayed a more significant heterogeneous distribution when compared with that of 1 degrees -HPT patients and normals. Moreover, the pB% displayed a nearly Gaussian distribution pattern from 20% to over 90% in patients with either 1 degrees-HPT or uremia. The specificity of this newly developed whole PTH(1-84) IRMA is the assurance, for the first time, of being able to measure only the biologically active whole PTH(1-84) without cross-reaction to the high concentrations of the aminoterminally truncated PTH fragments found in both normal subjects and patients. Because of the significant variations of pB% in patients, it is necessary to use the whole PTH assay to determine biologically active PTH levels clinically and, thus, to avoid overestimating the concentration of the true biologically active hormone. This new assay could provide a more meaningful standardization of future PTH measurements with improved accuracy in the clinical assessment of parathyroid function.

Intraoperative Parathyroid Hormone Analysis: A Study of 200 Consecutive Cases

Background: Immunoassays for parathyroid hormone (PTH), with short incubation times and results available in &lt;15 min, have allowed intraoperative monitoring of the success of parathyroid surgery. The purpose of this study was to evaluate the analytical performance of a rapid PTH assay and its clinical performance in a series of 200 patients.

Methods: PTH was measured with a modified immunochemiluminometric assay with a 7-min incubation time (QuiCk-IntraOperative™ Intact PTH assay). The rapid assay was compared with results in a central laboratory (immunoradiometric assay) in 44 EDTA-plasma specimens. The rapid assay was used intraoperatively in 200 consecutive cases with specimens analyzed before and 5–10 min after resection of the hypersecreting parathyroid gland(s).

Results: Intraassay imprecision was 12% at 28 ng/L and 11% at 278 ng/L. Regression analysis of results of the rapid PTH assay and the IRMA PTH assay in 44 parathyroidectomy patients yielded y = 1.26x − 12 ng/L, Sy|x = 26.3 ng/L, r = 0.984, and in 40 of 44 patients with values &lt;200 ng/L, y = 1.02x + 1.9, Sy|x = 13.9, r = 0.947. In the 195 cases using intraoperative PTH testing with complete results and defined clinical outcomes, the overall accuracy of the assay in predicting surgical success was 88% using the criterion of a 50% decrease at 5–10 min and 97% including the subset of patients with delayed decreases of PTH.

Conclusions: The rapid PTH assay had excellent analytical performance and excellent agreement with the PTH immunoradiometric assay and predicted the success of parathyroid surgery in this large series of consecutive patients.

One hundred consecutive minimally invasive parathyroid explorations

OBJECTIVE

To review the outcomes of 100 consecutive minimally invasive parathyroid explorations.

SUMMARY BACKGROUND DATA

Minimally invasive parathyroidectomy (MIP) has challenged the traditional approach of bilateral neck exploration for patients with primary hyperparathyroidism. Most patients with primary hyperparathyroidism have a single adenoma that when resected results in cure. It therefore appears logical to perform a directed approach to adenoma extirpation. MIP involves high-quality sestamibi images obtained with single photon emission computed tomography to localize enlarged parathyroid glands in three dimensions, limited exploration after surgeon-administered cervical block anesthesia, rapid intraoperative parathyroid hormone assay to confirm the adequacy of resection, and discharge within 1 to 3 hours of surgery.

METHODS

MIP was offered to 100 selected consecutive patients during an 18-month period beginning in March 1998.

RESULTS

Ninety-two cases were accomplished under cervical block anesthesia and 89 of these on an ambulatory basis. The cure rate was 100%, and there were no long-term complications. The mean hospital charge for MIP was less than 40% of that associated with traditional exploration.

CONCLUSIONS

Outpatient MIP appears to be the procedure of choice for most patients with primary hyperparathyroidism.

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

PURPOSE

This article illustrates the complementary nature of preoperative radionuclide parathyroid imaging and intraoperative rapid parathyroid hormone (PTH) assays in primary hyperparathyroid disease. The authors review the literature on these procedures and compare this protocol and its cost-effectiveness with those of the classic four-gland exploration.

MATERIALS AND METHODS

Preoperative parathyroid imaging with Tc-99m MIBI and intraoperative rapid PTH assays were performed at the time of neck exploration.

RESULTS

One of two parathyroid adenomas seen on radionuclide images would have been missed if the authors had relied solely on the initial decrease in PTH assay value to a normal level.

CONCLUSIONS

Tc-99m MIBI imaging and intraoperative rapid PTH assays are complementary; when used together, they lessen the likelihood that abnormal parathyroid glands will be overlooked. This experience and that of others suggest these combined procedures are cost-effective.

[Parathyroidectomy by elective route with perioperative measurement of parathyroid hormone. Report of 80 cases]

STUDY AIM

The aim of this study was to report a series of 80 patients treated by unilateral neck exploration for a sporadic primary hyperparathyroidism.

PATIENTS AND METHOD

Between April 1992 and November 1998, 80 patients (65 women and 15 men, mean age: 63.5 years) with a single gland enlargement localized by ultrasonography, were operated on through a short unilateral neck incision, under general anesthesia in 72 cases and local in eight cases. The enlarged gland was removed with intraoperative pathological examination and intraoperative monitoring of parathyroid hormone.

RESULTS

Mean duration of surgery was 25 minutes. There was no postoperative mortality or morbidity. Mean duration of hospital stay was two days. The enlarged gland was an adenoma in 75 cases and an hyperplasia in five. Adequate intraoperative parathyroid hormone decrease was observed. Postoperative calcemia was normal in 78 patients (97.5%). Among 76 surviving patients, with a 31-month follow-up, there was only a suspicion of persistent hyperparathyroidism in two patients.

CONCLUSIONS

Minimal invasive approach by unilateral neck exploration may be performed with safety and efficiency in patients with a single gland enlargement under intraoperative monitoring of parathyroid hormone.

Mixed-effects modeling of the pharmacodynamic response to the calcimimetic agent R-568

OBJECTIVE

The parathyroid cell calcium receptor is a novel drug target for affecting parathyroid hormone (PTH) secretion and for treating hyperparathyroidism. R-568 is a calcium receptor agonist that inhibits PTH secretion and increases calcitonin release in preclinical studies. The objective of this study was to evaluate the effect of R-568 on PTH plasma concentrations in humans.

METHODS

Eighteen healthy postmenopausal women were included in the study. Single ascending oral doses of 10 to 400 mg were administered in a randomized, placebo-controlled double-blind trial. PTH plasma concentrations were measured for up to 120 hours after each dose.

RESULTS

R-568 caused a dose-dependent decrease in plasma PTH, with peak effect observed within 1/2 to 2 hours after dosing. The maximum effect did not increase beyond doses from 80 to 160 mg, but duration of response increased at higher doses. An indirect-response model was developed to estimate the rates of input and output of the active moiety(ies), the inhibitory effect on PTH secretion, and the circadian variability in PTH. Population parameter estimates were 3.02 hour-1 and 0.49 hour-1 for rates of input and output of the active moiety(ies), respectively, IA50 (the unscaled amount of R-568 associated with 50% of Emax) was 16.3 mg, Emax (the maximum effect caused by R-568 expressed as a fraction of the rate of PTH secretion in the absence of any drug effect) was 89%, CPTH(baseline) (the baseline PTH plasma concentration in the absence of any drug effect) was 34.6 pg/mL, KePTH (the elimination rate constant for PTH) was 1.73 hour-1, amplitude of the circadian variability in PTH secretion was 5.8%, and the time of peak PTH secretion occurred at about 6 PM. Intersubject variability in parameter estimates ranged from 7% to 121%, and residual variability was 22%.

CONCLUSION

The model correctly described the onset, extent, and duration of effect on PTH after a wide range of doses of R-568.

Secondary hyperparathyroidism is an expected consequence of parathyroidectomy for primary hyperparathyroidism: a prospective study

BACKGROUND

Parathyroidectomy for primary hyperparathyroidism (PHPT) can cause secondary hyperparathyroidism, with increased serum parathyroid hormone (PTH) and normal or low serum calcium concentrations.

METHODS

A prospective study investigated 78 consecutive patients who underwent exploration for PHPT. Serum intact PTH and total calcium concentrations were measured the evening after operation and ionized Ca++ the following morning. These levels were reassayed 1 week later.

RESULTS

Before operation, the mean PTH level was 138 +/- 15 pg/mL, total calcium concentration was 11.6 +/- 0.1 mg/dL, and ionized Ca++ concentration was 1.44 +/- 0.02 mmol/L. On the night of the operation, the PTH level was 11 +/- 2 pg/mL, and the total calcium concentration was 8.9 +/- 0.1 mg/dL. Fifty-five patients had hypoparathyroidism, with a PTH level less than 10 pg/mL. The day after the operation, the ionized Ca++ level was 1.14 +/- 0.01 mmol/L. One week later, PTH, ionized Ca++, and total serum calcium concentrations returned to normal levels. In 9 patients (12%), PTH levels were increased (98 +/- 16 pg/mL), although ionized Ca++ concentrations were normal (1.18 +/- 0.02 mmol/L), demonstrating secondary hyperparathyroidism. Risk factors for postoperative secondary hyperparathyroidism included older age, symptomatic hyperparathyroidism, higher preoperative PTH and alakaline phosphatase levels, and lower serum phosphorous levels. In 70% of these patients, PTH levels returned to normal in 3 to 12 months.

CONCLUSIONS

Secondary hyperparathyroidism occurs in 12% of patients after surgical treatment of PHPT. It is transient, possibly compensating for relative hypocalcemia.

Improvements in parathyroid surgery in the intact 1-84 PTH assay era

BACKGROUND

Measurement of intact 1-84 parathormone (PTH) level by immunometric assays has been an important tool in the medical management of hypercalcaemia. The aim of the present study was to evaluate its practical contribution in the diagnosis and surgical treatment of primary hyperparathyroidism.

METHODS

The results of surgery were compared (number of failed and inadequate cervicotomies, number of overlooked cervical glands) in two groups of primary hyperparathyroid patients operated on without (group I, n = 624) and with (group II, n = 360) intact PTH evaluation. The postoperative intact PTH level was measured 1-50 months after surgery in 109 unselected normocalcaemic patients. The benefit of intact PTH assay was studied in borderline patients. We tried to settle a correlation between parathyroid resected weight and intact PTH pre-operative level in different subsets of the disease.

RESULTS

The sensitivity for the diagnosis of primary hyperparathyroidism was 86.6% for intact PTH level alone, and 95.9% when plotted with synchronous serum total calcium. Hyperfunctional adenoma was incidentally discovered in 14 asymptomatic normocalcemic normo-PTH patients. The predictive positive value of intact PTH assay for the diagnosis of primary hyperparathyroidism was 99.3%. Intact PTH assay often affirmed the diagnosis of primary hyperparathyroidism in borderline cases. The postoperative intact PTH measurement was not a good indicator for evaluating the late outcome in seemingly cured patients. Sharp but statistically significant correlation was found between the resected weight and the intact PTH level. The discovery of a small adenoma in a patient with high intact PTH level, bone disease and low vitamin D level should raise suspicion of a second hyperfunctioning gland.

CONCLUSIONS

Intact PTH assay was a main contributor to the surgical management of primary hyperparathyroidism, reducing the number of unnecessary cervicotomies and enabling the cure of all cases of primary hyperparathyroidism except those due to mediastinal glands. It raised unanswered problems in the late postoperative course.

Revascularisation of human parathyroid tissue transplanted to athymic mice

The revascularisation process of transplanted human normal, hyperplastic and adenomatous parathyroid tissue was analysed at 2 and 4 days and 1, 2, 4, 7 and 12 weeks after transplantation to athymic mice. The transplants were examined by light and electron microscopy, immunohistochemistry and autoradiography. Vessels were detected by monoclonal antibodies specific for mouse and human endothelial cells. Immunohistochemistry demonstrated ingrowth of vessels from the host into the transplant and at one week numerous capillary sprouts were observed in the peripheral parts of the transplants. During the first week, peak levels of proliferation (labelling index) were observed in endothelial cells and capsular fibroblasts, and the proliferative capacity of endothelial cells was most pronounced in adenoma transplants. Fenestrated capillaries were observed in hyperplastic and adenomatous transplants, but not in transplants of normal tissue. In conclusion, revascularisation of transplanted human parathyroid tissue is enabled by ingrowth of vessels from the host into the transplant. The proliferative capacity of endothelial cells is higher and the process of maturation is faster in hyperplastic and adenomatous tissue compared to normal tissue.

SOME CHARACTERISTICS OF PRIMARY HYPERPARATHYROIDISM IN VIETNAMESE IMMIGRANTS LIVING IN SOUTHERN CALIFORNIA

OBJECTIVE

To characterize primary hyperparathyroidism (PHP) in Vietnamese immigrants living in southern California and to summarize the results of treatment.

METHODS

We describe 11 patients (8 women and 3 men) with a mean age of 57.91 years who underwent follow-up from 1991 to 1995 after PHP was diagnosed. The patients had no specific complaints. Four patients had a history of kidney stones, and five had chronic hypertension. Only five patients had high levels of total serum calcium; the other six patients had normal or fluctuating levels of total serum calcium. All patients, however, had high levels of intact parathyroid hormone (PTH) and ionized calcium. Preoperatively, parathyroid imaging with technetium-99m sestamibi demonstrated persistently increased parathyroid gland uptake.

RESULTS

In all nine patients who underwent surgical treatment, an adenoma was found in the parathyroid glands; two patients refused operative intervention. The mean serum phosphate was in the low-normal range and increased postoperatively (2.70 versus 3.52 mg/dL; P<0.001). The mean serum chloride level also decreased postoperatively (104.62 versus 100.78 mEq/L; P<0.001). The ratio of chloride/phosphate decreased significantly after adenoma removal (39.44 versus 29.21; P<0.001). Six patients received calcium gluconate either alone or in combination with vitamin D supplements for hypocalcemia postoperatively. The other three patients, however--who did not receive calcium supplements postoperatively--had persistently high levels of intact PTH but normal serum Ca++ levels and subsequently were treated effectively with calcium gluconate and vitamin D.

CONCLUSION

The presence of hypercalcemia, especially Ca++, and an increased level of intact PTH establishes the diagnosis of PHP. After parathyroidectomy, the persistence of high levels of intact PTH in association with normal serum Ca++ suggested the presence of secondary hyperparathyroidism, which was treated effectively with calcium gluconate and vitamin D. These patients had the same clinical picture as other ethnic groups with PHP, but they needed either calcium alone or calcium and vitamin D supplements after parathyroidectomy because of their bone loss from prolonged PHP.

Parathyroid function and bone metabolic markers in primary and secondary hyperparathyroidism

Remarkable changes of parathyroid function immediately after parathyroidectomy were evaluated in primary (PHPT) and secondary (RHPT) hyperparathyroidism. Bone metabolism was also evaluated by new specific markers of bone formation and resorption. A rapid decline into the undetectable range, and a rapid recovery of serum bioactive parathyroid hormone (PTH) concentrations were observed after parathyroidectomy in PHPT. Since the function of the remnant parathyroid glands was not clear, we investigated the transcription of PTH mRNA. Despite the suppression of PTH secretion in the remnant parathyroid glands, no significant difference was found in the amount of PTH mRNA present in an adenoma as compared to a remnant gland when evaluated by cytoplasmic dot hybridization and in situ hybridization. Although measurement of serum PTH concentration by assays of inactive fragment was available for the longterm follow-up of PTH function in RHPT, parathyroid function should be evaluated by biologically active intact PTH immediately after operation. The PTH gradient also was successfully evaluated by the measurement of intact PTH. A discrepancy was observed between bone resorption evaluated by type I collagen cross-linked N-telopeptide as compared to bone formation evaluated by osteocalcin immediately after operation. This discrepancy will improve and bone mineral density will increase in the first 6 months after parathyroidectomy.

Blood supply and parathyroid hormone secretion in pathological parathyroid glands

The blood supply of pathologic parathyroid glands and the relation between parathyroid hormone secretion and parathyroid blood perfusion was studied during surgery for hyperparathyroidism. Blood flow in 39 single adenomas and 20 glands classified as primary or secondary hyperplasia were studied intraoperatively with laser Doppler flowmetry. The ipsilateral inferior thyroid artery was occluded during continuous flowmetry recording, which resulted in a 40% reduction of parathyroid blood flow in both groups. In 12 patients with single adenomas, intact parathormone (iPTH) was measured intraoperatively before and during occlusion of the ipsilateral inferior thyroid artery and after extirpation of the adenoma. During occlusion the iPTH levels were mainly unchanged despite blood flow reduction of up to 80%. After removal of the adenoma the iPTH normalized within 15 minutes. In a control group of eight single adenomas, iPTH was measured similarly without vascular occlusion, demonstrating comparable iPTH levels. This study demonstrates similar routes of vascularization for single adenomas and hyperplastic glands, as was earlier seen for normal parathyroid glands. The increased parathyroid hormone secretion from single adenomas appears to remain mainly unchanged during significant blood flow reduction.

Transient rise in intact parathyroid hormone concentration after surgery for primary hyperparathyroidism

Two-site immunometric assays for determination of the level of intact parathyroid hormone (PTH) in serum have enabled detailed clinical studies of PTH secretion. Fifty-one patients with primary hyperparathyroidism were studied before surgery and 2 years after operation. PTH levels dropped to low values after operation. A rebound increase in PTH concentration occurred from 10 days to 3 months after surgery. Abnormally raised postoperative PTH concentrations were noted in 31 per cent of the patients, who had lower serum concentrations of ionized calcium (Ca2+) than the rest (P < 0.003). Before operation these patients had a more pronounced hyperparathyroidism than the others. At 2 years after surgery there was still a positive correlation between PTH concentrations before and after surgery (P < 0.001). The rebound increase in the level of PTH was a general phenomenon probably caused by low Ca2+ concentrations at the time of remineralization of bone. This phenomenon was transient. The positive correlation between preoperative and postoperative PTH concentrations shows that effects of hyperparathyroidism can remain for a long time after surgical cure.

Early postoperative plasma calcium concentration as a predictor of the need for calcium supplement after parathyroidectomy

This study evaluated early postoperative serum calcium concentration as a predictor of hypocalcaemic symptoms and the need for calcium supplements. A total of 64 consecutive patients undergoing curative parathyroidectomy for primary hyperparathyroidism were studied. Twenty patients (31 per cent) developed hypocalcaemic symptoms requiring calcium supplements. Plasma calcium levels in the preoperative and early postoperative periods were similar in patients who required calcium supplements and those in whom they were not necessary. There was no significant difference in the percentage decrease in early calcium levels after operation between the two groups. In those undergoing reoperative surgery and subtotal parathyroidectomy the percentage decline was significantly higher in patients who required calcium supplements (12.8 versus 5.6 per cent, P < 0.005). A fall of 10 per cent or more was consistently followed by hypocalcaemic symptoms. Calcium determination in the early postoperative period is of little value in predicting the onset of hypocalcaemic symptoms.

Resetting of parathyroid hormone secretion after vitamin D3 treatment in hypoparathyroidism and after parathyroid adenectomy in primary hyperparathyroidism

The relationship between parathyroid hormone (PTH) secretion and extracellular calcium (Ca) level is reciprocal causality. The equilibrium operating point determines basal PTH secretion rate and basal extracellular Ca level. We studied how this equilibrium was achieved in the subjects with decreased PTH secretion or decreased parathyroid glands number. Basal/maximum ratio of serum PTH, which reflects the basal secretory state of parathyroid glands, was increased in 9 hypoparathyroid patients treated with vitamin D3 (VD3) [7 patients with idiopathic hypoparathyroidism] and in seven of nine parathyroid adenectomized patients. There was a negative correlation between the ratio and basal serum Ca level in the patients with IHP after VD3 treatment (r = 0.7167, P < 0.05) and in the patients after parathyroid adenectomy (r = 0.7760, P < 0.05). The regression curves in these two groups coincided regardless of the difference in maximum PTH secretion rate, which suggested that the basal secretory state of parathyroid glands was determined by extracellular Ca level in a similar manner in these subjects. There was a sigmoidal relationship between basal/maximum ratio of serum PTH and basal serum Ca level, when the data were collected from 15 hypoparathyroid patients before or after VD3 treatment, 9 parathyroid adenectomized patients, and 10 normal subjects (r = 0.9057, P < 0.001). This sigmoidal curve is thought to represent the fundamental relationship between the basal secretory state of parathyroid glands and extracellular Ca level.

Hypocalcemic emergencies

Chronic hypocalcemia occurs frequently, although emergent hypocalcemia does not. When hypocalcemia is suspected, verification of ionized hypocalcemia is required and an etiopathologic search warranted. Etiology-specific therapy is suggested, although at times emergent intravenous calcium is indicated. Long-term nonspecific therapy includes oral calcium and vitamin D supplementation.

Serum parathormone profile during surgical treatment of hyperfunctioning parathyroid adenoma: a multicompartmental model

Patterns of intact parathyroid hormone (iPTH) elimination and subsequent recovery of parathyroid function were studied in seven patients undergoing surgical removal of solitary hyperfunctioning parathyroid adenoma. Using a sensitive two-site immunoradiometric assay, iPTH levels were measured pre, peri-, and postoperatively. Blood samples were taken at very early and at late stages, including 3, 6, 9, and 15 minutes and 48, 72, and 96 h after adenomectomy. A biexponential formula was calculated to fit the decreasing values of iPTH in all patients. The PTH half-life in the early phase was 1.4 +/- 1.1 minutes (95% confidence limits). The PTH half-life in the second phase was 64.45 +/- 32.19 minutes (95% confidence limits). A third phase is represented by a slow, linear increase in plasma iPTH values as a result of the recovery of healthy suppressed parathyroid glands. The extrapolation to baseline of the later phase shows that the recovery of normal parathyroid function begins as soon as 240 minutes after adenomectomy and is independent of the decrease in PTH of adenomatous origin. All individual results were consistent with this model. Five patients had iPTH values below 5 pg/ml, one had 15 pg/ml, and the last had 27 pg/ml 5 h after parathyroid adenomectomy. The recovery of the hormonal activity of the remaining glands occurred rapidly. By the postoperative hour 24 the mean serum iPTH concentration was 12.28 +/- 8.07 pg/ml. The intraoperative serum iPTH concentration offers a model to assess both recovery of hormonal secretion from functionally suppressed parathyroid glands and disappearance of parathyroid hormone.

Intraoperative monitoring of parathyroid procedures by a 15-minute parathyroid hormone immunochemiluminometric assay

OBJECTIVE

To report the recent development and validation of a sensitive 15-minute immunochemiluminometric assay (ICMA) of parathyroid hormone (PTH).

DESIGN

The characteristics and applications of a new "rapid" PTH ICMA are described, and the advantages in comparison with other assays are discussed.

MATERIAL AND METHODS

The 15-minute PTH ICMA was achieved by using a higher incubation temperature (45 degrees C rather than room temperature) and a concentration of tracer antibodies that was 5 times that in the regular 18-hour assay. The sensitivity, recovery, and linearity of dilution of the rapid ICMA were assessed, as was its ability to reflect intraoperative changes in PTH concentration after parathyroidectomy in patients with hyperparathyroidism.

RESULTS

The sensitivity of the ICMA was 0.3 pmol/L in comparison with 0.08 pmol/L for the regular 18-hour assay (normal range, 1.0 to 5.0). The recovery of added PTH was 84% by using ethylene-diaminetetraacetic acid-plasma as the specimen. Moreover, the linearity of specimens after dilution was good. The assay demonstrated a rapid response to parathyroid gland removal. In most patients, PTH levels declined precipitously (to less than 30% of basal values) within 5 minutes after parathyroid resection. PTH levels remained low to undetectable at 10 and 20 minutes after excision.

CONCLUSION

This rapid PTH ICMA may be of assistance to endocrine surgeons in the monitoring of PTH function after both parathyroid and thyroid surgical procedures.

Intraoperative monitoring of intact PTH during surgery for primary hyperparathyroidism

The intraoperative differential diagnosis between adenoma and hyperplasia during surgery for primary hyperparathyroidism (pHPT) is sometimes difficult. Several methods have been proposed to aid the surgeon in deciding on the amount of parathyroid tissue to be resected. We examined the use of intraoperative monitoring of intact PTH in 47 patients operated upon for pHPT. The highly sensitive assay for intact PTH was modified to permit a total turn-around time from gland excision to obtained result of about 60 min. The correlation (r) between the results of the modified and the conventional method, which requires 24 h of incubation, was 0.98. At 15 min after removal of the parathyroid adenoma the levels of intact PTH had decreased by [mean (SD)] 85 (11)%. A decrease of 63% in intact PTH in patients with parathyroid adenoma predicted with 95% confidence the 4 patients with primary hyperplasia as not having parathyroid adenoma. We conclude that intraoperative measurement of intact PTH could be a valuable adjunct to surgical skill, especially for reoperative parathyroid surgery.

Suppressibility of serum levels of PTH by calcium in the immediate postoperative period after surgery for primary hyperparathyroidism

The ability of calcium to suppress the secretion of parathyroid hormone (PTH) is impaired in primary hyperparathyroidism (pHPT). Whether the nonadenomatous glands in pHPT also exhibit altered calcium/PTH homeostasis is not known, but this may be the case since in the immediate postoperative period after surgery for pHPT, hypocalcemia often evolves in spite of a rapid normalization of serum levels of PTH. In this study, therefore, the suppression of serum levels of PTH by an oral calcium load was investigated pre- and postoperatively in 12 patients operated on for parathyroid adenoma. There was no difference in the calcemic response during the calcium load pre- and postoperatively. We found that the suppression of serum levels of PTH by calcium was increased already on the first postoperative day. However, postoperatively, the suppression of serum levels of PTH correlated positively to serum levels of ionized calcium and, furthermore, negatively to the weight of the excised parathyroid adenoma and the preoperative serum levels of ionized calcium. The results indicate that the function of the remaining parathyroid glands in patients with parathyroid adenoma could have been altered during the hyperparathyroid state and that postoperative hypocalcemia more readily evolves in patients with severe pHPT and impaired suppressibility of PTH (by calcium) in the remaining parathyroid glands.

Single-dose intravenous therapy with pamidronate for the treatment of hypercalcemia of malignancy: comparison of 30-, 60-, and 90-mg dosages

PURPOSE

To determine the efficacy, dose-response relationship, and safety of 30, 60, and 90 mg of a single intravenous dose of an aminobisphosphonate, pamidronate (APD), for the treatment of moderate to severe hypercalcemia of malignancy.

PATIENTS AND METHODS

Patients with histologically proven cancer and a corrected serum calcium level of at least 12.0 mg/dL after 48 hours of normal saline hydration were enrolled in a double-blind, multicenter, randomized clinical trial. Pamidronate in 30-, 60-, or 90-mg doses was administered as a single 24-hour infusion. Serum calcium corrected for albumin, urine hydroxyproline, and calcium excretion, and serum parathyroid hormone (PTH) (1-84) were determined before and after pamidronate therapy.

RESULTS

Thirty-two men and 18 women entered the study. A dose-response relationship for normalization of corrected serum calcium was seen after pamidronate administration. Corrected serum calcium normalized in 40% of patients who received 30 mg, in 61% of patients who received 60 mg, and in 100% of patients who received 90 mg of pamidronate. The decline in the serum calcium level was associated with decreased osteoclastic skeletal resorption evidenced by a decrease in urine calcium and hydroxyproline excretion. Among those with a normalized corrected serum calcium level, the mean (median) duration of normalization of the corrected serum calcium value was 9.2 (4), 13.3 (5), and 10.8 (6) days in the 30-, 60-, and 90-mg treatment groups, respectively. The response of hypercalcemia to pamidronate was not significantly influenced by the presence of skeletal metastases. PTH 1-84, suppressed in patients on entry into this study, increased to a greater extent in those patients with osteolytic skeletal metastases compared with those with humoral hypercalcemia of malignancy. Clinical improvement, including improved mental status and decreased anorexia, accompanied the decline in the corrected serum calcium level in all three treatment groups. Side effects included low-grade fever, asymptomatic hypocalcemia, hypomagnesemia, and hypophosphatemia.

CONCLUSIONS

A single-dose infusion of 60 to 90 mg of pamidronate was highly effective and well tolerated and normalized corrected serum calcium in nearly all patients (61% to 100%) with hypercalcemia of malignancy.

Hypocalcemic emergencies

The approach to the hypocalcemic patient is best considered with due regard to the underlying etiology and the extent to which features of hypocalcemia are present. When hypocalcemia is a medical emergency, aggressive but judicious measures must be taken immediately to correct, in part, the hypocalcemia. Parenteral therapy of hypocalcemia is advisable only under these conditions. The aim of acute management is not to return the serum calcium to normal but rather to ameliorate the acute manifestations of hypocalcemia. If the hypocalcemic state is owing to a chronic condition that will not remit, a plan for long-term management with a vitamin D preparation and calcium supplementation is implemented after the emergency therapy is provided.

Intraoperative urinary cyclic AMP monitoring in primary hyperparathyroidism

OBJECTIVE

This study examined the utility of intraoperative urinary cyclic 3'5' adenosine monophosphate (UcAMP), an indicator of parathyroid (PTH) hormone end-organ activity, as a "biochemical frozen section," signaling the real-time resolution of PTH hyperactivity during surgery for primary hyperparathyroidism.

SUMMARY BACKGROUND DATA

The unsuccessful initial neck exploration for primary hyperparathyroidism, leaving the patient with persistent hyperfunctioning parathyroid tissue, results in part from the surgeon's inability intraoperatively to correlate a gland's gross appearance and size estimation with physiologic function. Preoperative imaging, intraoperative imaging, and intraoperative histologic/cytologic surveillance have not resolved this dilemma.

METHODS

Twenty-seven patients underwent a prospective intraoperative UcAMP monitoring protocol. The patients all had a clinical diagnosis of primary hyperparathyroidism and an average preoperative serum calcium of 12.0 +/- 0.3 mg/dl. UcAMP was assayed intraoperatively using 20-minute nonequilibrium radioimmunoassay providing real-time feedback to the operating team.

RESULTS

All patients had an elevated UcAMP confirming PTh hyperactivity at the beginning of the procedure. One patient, subsequently found to have an supernumerary ectopic adenoma, had four normal glands identified intraoperatively, and his intraoperative UcAMP values corroborated persistent hyperparathyroidism, the UcAMP of the remaining 26 patients decreased from 7.0 +/- 1.1 to 2.7 +/- 0.7 nm.dl GF (p < .00005) after complete adenoma excision, and they remain normocalcemic. The protocol provided useful and relevant information to the operating team, and aided in surgical decision-making, in 10 of the 27 cases (37%).

CONCLUSION

Intraoperative biochemical surveillance with ucAMP monitoring reliably signals resolution of PTH hyperfunction. It is a useful adjunct to the surgeon's skill, judgment, and experience in parathyroid surgery.

Calcium regulating hormones after oral and intravenous calcium administration

The aim of this study was to determine the changes in serum calcium concentration and in the concentrations of calcium regulating hormones after a single oral or intravenous calcium administration. Standard dosages of calcium, as used in routine patient care, were employed. Intact parathyrin, calcitonin, calcitriol, calcidiol, total calcium, ionized calcium, total protein and phosphate were determined in 12 healthy young men before and up to 8 h after oral and intravenous administration of calcium. During a fortnight there were four study days with 1000 mg calcium orally (p.o.), 2000 mg orally, 180 mg calcium intravenous (i.v.) and a control day without calcium. During the study the men were on a low calcium diet. We observed a sharp increase in the calcium concentration after i.v. administration (15 min: total Ca: + 0.48 +/- 0.32 mmol/l; ionized Ca: + 0.25 +/- 0.15 mmol/l; p < 0.01). The concentration increase after the two oral loads was nearly identical. The maximal concentration of total calcium was reached after 120 min (1000 mg: + 0.1 +/- 0.04 mmol/l; p < 0.001; 2000 mg: + 0.12 +/- 0.04 mmol/l; p < 0.001). There was a significant increase in urinary calcium after all modes of calcium administration. Calcitonin increased significantly only after i.v. injection of calcium (+ 9.2 +/- 3.4 pmol/l; p < 0.001) while parathyrin decreased significantly after all modes of calcium administration (i.v.: 15 min: -1.9 +/- 0.88 pmol/l; p < 0.01; 1000 mg: 90 min: -0.78 +/- 0.75 pmol/l; p < 0.001; 2000 mg: 90 min: -1.02 +/- 0.57 pmol/l; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamics of parathyroid hormone release and serum calcium regulation after surgery for primary hyperparathyroidism

Analysis of 14 patients with primary hyperparathyroidism (HPT) prior to and during the first year after parathyroid surgery disclosed that the operation was associated with rapid reductions of intact serum parathyroid hormone (PTH) and total serum and ionized plasma calcium values. A decreased urinary calcium excretion, a gradual elevation of renal calcium reabsorption, a transient reduction of serum calcitriol, and a late increase in 25-hydroxycholecalciferol values were also noted. Dynamic tests of parathyroid function by EDTA infusion and an oral calcium load revealed a sigmoidal relationship between serum PTH and calcium levels, and that parathyroid surgery induced considerable changes in both the position and slope of the dose-response curve. It was also apparent that PTH release was submaximally stimulated event at periods of hypocalcemia. The findings substantiate that adjustments of PTH release to acute alterations of serum calcium occur along the prevailing dose-response relationship, while stimuli being maintained for longer periods of time induce compensatory shifts in the position and slope of this curve. It is further suggested that unknown factors with PTH-like function may participate in the calcium regulation after surgery for primary HPT.

Clinical evaluation of a rapid parathyroid hormone assay

Modifications to the incubation conditions of radioimmunoradiometric assay for whole molecule parathyroid hormone (PTH) permit accurate quantification of the hormone in the peripheral circulation within 1 h of sampling. We assessed the assay intraoperatively in 75 patients undergoing parathyroidectomy. Serum PTH concentration declined to less than 20% of its pre-operative value within 20 min of the successful completion of surgery provided that renal function was normal. In patients with chronic renal failure the rate of decline in serum PTH concentration after parathyroidectomy was slower in some cases. In four cases of unsuccessful parathyroidectomy, serum PTH concentration remained above 60% of its preoperative value. Intraoperative monitoring during parathyroidectomy using this rapid PTH assay offers considerable advantages to the surgeon over frozen section.

Immunoassays for parathyroid hormone 1-84 in the diagnosis of hyperparathyroidism

The two most frequent causes for hypercalcemia are primary hyperparathyroidism and hypercalcemia associated with malignancy. Elevated or inappropriately high PTH serum levels are the hallmark of hyperparathyroidism. Sensitive immunometric assays for the secreted, biologically active, intact parathyroid hormone molecule, PTH-(1-84), employ two populations of region-specific antibodies, take advantage of saturation kinetics rather than competitive binding, and have many technical advantages over conventional radioimmunoassay. Approximately 90% of patients with primary hyperparathyroidism have elevated serum levels of PTH-(1-84) by immunometric assay; the remainder have inappropriately elevated values of PTH for the serum calcium concentration. Clinical correlation studies comparing measurements of PTH using antisera that recognize the carboxyl, midregion, or amino terminus of PTH with PTH levels determined by immunometric assays demonstrate elevated values in equivalent numbers of hyperparathyroid individuals. Immunometric assays for PTH-(1-84) have their greatest value in separating patients with hyperparathyroidism from those with hypercalcemia of malignancy. In earlier studies using region-specific antisera, there was virtually always an overlap of serum PTH levels in hyperparathyroidism and hypercalcemia associated with malignancy. In contrast, analysis of results using PTH-(1-84) immunometric assays in several hundred reported patients shows a complete separation of PTH values. Clinical judgment, combined with measurement of PTH in the setting of hypercalcemia, can lead to the diagnosis of hyperparathyroidism with confidence in essentially all patients.

Compensatory parathyroid hypertrophy after hemiparathyroidectomy in rats feeding a low calcium diet

The functional and anatomic compensatory response of the parathyroid gland was examined in hemiparathyroidectomized (HPTx) rats whose parathyroid hormone (PTH) secretion was stimulated by a low calcium diet. These responses were compared with those observed in the thyroid gland of hemithyroidectomized (HTx) rats. Rats kept on a low calcium diet for 10 days were subjected to HPTx, HTx, or sham operations. Throughout the experiment (up to 28 days after surgery), serum calcium levels of HPTx rats were lower than the basal, with delta values (mg/dl, mean +/- SEM) of -0.66 +/- 0.17 and -0.84 +/- 0.17, (P less than 0.05) 3 and 28 days after surgery, respectively. Serum PTH decreased significantly from 7 to 21 days after HPTx, reaching normality at day 28 after surgery. In HTx rats, serum thyroxine (T4) levels diminished significantly 7 days after surgery, and attained normality thereafter. The mitotic index (number of metaphases/1,000 cells) in parathyroid glands of colchicine-treated HPTx rats increased significantly in comparison to sham-operated controls, when examined 2 or 40 days after surgery. The mitotic index of thyroid follicular cells was significantly higher than that of their respective controls, 2 but not 40 days after HTx. These results indicate that after HPTx, a delayed compensatory response is found when the animals are kept under a low calcium diet. Parathyroid response is both delayed and of a minor degree compared to that found in the thyroid gland after HTx.