A prospective evaluation of novel methods to intraoperatively distinguish parathyroid tissue utilizing a parathyroid hormone assay

BACKGROUND: Frozen section analysis has traditionally been used to confirm the identity of parathyroid tissue intraoperatively; however, it is time-consuming and costly and requires the excision of a significant portion of tissue. An intraoperative biopsy and analysis with a parathyroid hormone (PTH) assay is a possible alternative; however, this technique has not been perfected. METHODS: Two hundred twenty-three tissue specimens were collected prospectively from patients undergoing neck exploration. Each specimen was sampled intraoperatively using three different biopsy techniques: a fine-needle aspiration (FNA) with 10 passes of a needle (FNA10), a FNA with 20 passes of a needle (FNA20), and a tissue biopsy of approximately 1.0 mm3 (BIOPSY). The PTH concentration of each sample was determined via the Elecsys 1010 PTH immunoassay. The final tissue diagnosis was determined by histology or operative data. RESULTS: Parathyroid samples from all techniques had higher median PTH concentrations than nonparathyroid samples. However, the accuracies for the detection of parathyroid tissue varied markedly (PTH cutoff of 1000 pg/ml): the accuracies of the FNA10 and FNA20 were 71 and 80%, respectively, while the BIOPSY was 99% accurate. CONCLUSIONS: This is the first prospective study evaluating multiple methods to diagnose parathyroid tissue intraoperatively using a rapid PTH assay. We conclusively show that the BIOPSY technique is 99% accurate for the diagnosis of parathyroid tissue, and therefore, should be the method of choice when the intraoperative confirmation of parathyroid tissue is needed.     

Direct in vitro evidence of the suppressive effect of cinacalcet HCl on parathyroid hormone secretion in human parathyroid cells with pathologically reduced calcium-sensing receptor levels

Clinical studies have been performed to determine the effect of cinacalcet HCl (cinacalcet), an allosteric modulator of the calcium-sensing receptor (CaR), on primary hyperparathyroidism (PHPT) and secondary hyperparathyroidism of uremia (SHPT). However, no in vitro studies on human parathyroid cells have been reported to date. In this study, the inhibitory effect of cinacalcet on PTH secretion was analyzed in primary cultured parathyroid cells obtained from patients. The investigation involved three PHPT and three SHPT patients subjected to therapeutic parathyroidectomy. Notably, all SHPT patients were resistant to intravenous vitamin D analogue therapy. Removed parathyroid tumors were used for immunohistochemistry and parathyroid cell primary culture. Immunohistochemical analyses revealed diminished expression of CaR and vitamin D receptor (VDR) in all parathyroid tumors. PTH secretion from cultured parathyroid cells of PHPT and SHPT patients was suppressed by extracellular Ca²⁺ and cinacalcet in a dose-dependent manner. Rates of suppression of PTH secretion in PHPT and SHPT by cinacalcet (1000 nmol/l) were 61% ± 21% and 61% ± 19%, respectively. Cinacalcet demonstrates significant potency in the suppression of PTH secretion in primary cultured human parathyroid cells in vitro, despite reduced levels of the target protein, CaR. Data from this in vitro analysis support the clinical application of cinacalcet in PHPT and SHPT therapy.     

Evaluation of parathyroid hyperplasia by ultrasonographic examination in patients with end-stage renal failure before and at initiation of dialysis

SUMMARY:   Secondary hyperparathyroidism (2HPT), which is related to renal osteodystrophy (ROD), may occur in patients in the comparatively early stage of chronic renal failure (CRF). Secondary hyperparathyroidism patients with parathyroid hyperplasia showed resistance to vitamin D₃ treatment during long-term dialysis. At present, evaluation by ultrasonography is considered to be useful for confirming parathyroid hyperplasia. There are no clinical data associated with imaging evaluation of 2HPT in CRF patients. In the present study, the relationship among clinical and biochemical data, and parathyroid hyperplasia by ultrasonography, was evaluated in 12 patients (six males and six females) with end-stage renal failure (ESRF) before and at initiation of dialysis. Five patients showed an enlargement of parathyroid glands in ultrasonography. Levels of serum-intact parathyroid hormone (PTH) in patients with parathyroid hyperplasia (positive group) were significantly higher than in those without hyperplasia (negative group; 97.6 ± 36.65 vs 17.4 ± 4.45 pmol/L; P  < 0.05). The levels of intact PTH were above 35.0 pmol/L in all five patients with hyperplasia. All patients in the positive group had never taken vitamin D₃ supplements. Calcium-containing phosphate binders were not prescribed before the present study, except in one patient. Parathyroid hyperplasia caused by 2HPT was recognized in patients before and at initiation of dialysis in this study. It appears that untreated 2HPT in CRF patients may progress to advanced 2HPT in ESRF before and/or after the early stage of dialysis. The levels of serum intact PTH are useful in predicting parathyroid hyperplasia.     

Reoperative parathyroidectomy in 228 patients during the era of minimal-access surgery and intraoperative parathyroid hormone monitoring

Background

Reoperative parathyroidectomy (R-PTX) in primary hyperparathyroidism (1HPT) has increased failure rates and morbidity. This study evaluated R-PTX during the era of minimal-access PTX with intraoperative parathyroid hormone (IOPTH) monitoring.

Methods

Two thousand sixty-five patients with 1HPT who underwent PTX were assessed for R-PTX. Preoperative studies, operative findings, and outcomes were evaluated.

Results

Two hundred twenty-eight patients underwent 236 R-PTX procedures. Imaging performed included sestamibi (89%), ultrasound (US; 56%), computed axial tomography/magnetic resonance imaging (5%), and selective venous sampling (1%). Sestamibi was more sensitive than US (84% vs 68%). Curative surgery was performed in 89% of patients. IOPTH was 99% sensitive. There was no relationship between cure and the following parameters: preoperative calcium or PTH levels, persistent or recurrent disease, or use of IOPTH. Solitary gland disease and a single previous operation were associated with increased likelihood of cure (P = .06). Hypoparathyroidism was decreased using IOPTH monitoring (2% vs 9%). One patient had recurrent laryngeal nerve palsy.

Conclusions

R-PTX can be performed effectively with minimal complications. IOPTH is an accurate predictor of cure and may decrease the frequency of permanent hypoparathyroidism.     

Intact parathyroid hormone levels in renal transplant patients with normal transplant function

Bleskestad IH, Bergrem H, Leivestad T, Gøransson LG. Intact parathyroid hormone levels in renal transplant patients with normal transplant function.
Clin Transplant 2011: 25: E566–E570. © 2011 John Wiley & Sons A/S. Abstract: Introduction: Chronic kidney disease mineral and bone disorder (CKD‐MBD) is common in patients who have undergone kidney transplantation. There is limited information on the extent to which patients with normal renal function after transplantation have persistent disturbances in their mineral metabolism. Aim: The aim of the study is to investigate the prevalence of elevated intact parathyroid hormone (iPTH) levels at least one yr after transplantation in patients living with a first renal transplant with normal transplant function. Methods: A retrospective, observational study of 607 patients was collected from the Norwegian Renal Registry. Of these, iPTH was recorded for 360 patients. Results: One hundred and eighty‐eight patients (52%) had elevated iPTH levels. Twenty‐six patients (7%) had iPTH levels >2.5 times the upper limit of normal (ULN). Patients with a pre‐emptive transplant were significantly younger than the patients who had received treatment with dialysis (p < 0.0001). The prevalence of iPTH > ULN was significantly higher in patients with a pre‐emptive transplant (p = 0.037). Conclusions: In post‐transplant patients with normal transplant function, our data indicate that more than 50% have elevated levels of iPTH more than one yr after transplantation. If elevated iPTH level is associated with mortality in this patient population, it may have major impact on clinical treatment guidelines.     

Estimated weight of the residual parathyroid gland after parathyroidectomy using plasma levels of the parathyroid hormone

The possibility of estimating the total weight of the parathyroid glands based on the plasma concentration of the parathyroid hormone (PTH) would be of great help when searching for the parathyroid glands during surgery on patients with secondary hyperparathyroidism. Thus, we studied the relationship between the levels of carboxylterminal PTH (C-PTH), midportion PTH (M-PTH) and intact PTH, and the weight of the parathyroid glands resected for secondary hyperparathyroidism. The subjects studied were 11 patients with secondary hyperparathyroidism caused by chronic renal failure. The pre- and post-operative differences in the plasma C-PTH levels and plasma M-PTH levels were significantly correlated with the weight of the resected parathyroid glands (p<0.001 for both), but there was no correlation between the differences in the levels of intact PTH and the weight of the resected parathyroid glands. From these relationships we estimated the weight of the residual parathyroid gland after parathyroidectomy using the levels of each PTH. All patients in whom the residual parathyroid gland was estimated to be heavy based on the levels of M-PTH showed recurrence of hyperparathyroidism after the parathyroidectomy. We therefore found that estimation of the weight of the parathyroid glands from the levels of M-PTH is both possible and useful.     

Significance of rebounding parathyroid hormone levels during parathyroidectomy

Background

Using minimally invasive parathyroidectomy (MIP), most surgeons require a 50% decline in intraoperative parathyroid hormone (IoPTH) to determine cure, but the significance of IoPTH kinetics occurring after this drop remains unknown. The aim of this study was to determine the impact of IoPTH levels that first meet criteria for cure, but then increase again, or rebound, between 10 and 15 min postexcision.

Methods

We conducted a retrospective review of patients undergoing initial parathyroidectomy for primary hyperparathyroidism at our institution from 2001 to 2011. Rebound IoPTH was defined as an increase in parathyroid hormone ≥5 pg/mL after achieving the 50% drop required for cure. Comparisons were evaluated with the Student t-test, chi-square test, or Fisher exact test where appropriate.

Results

Of the 1386 patients who met selection criteria, 86 (6.2%) patients exhibited rebound IoPTH. The mean magnitude of rebound was 13.8 ± 3.6 pg/mL. Compared with those not displaying rebound, more patients with rebound IoPTH were treated with open parathyroidectomy rather than MIP (10.8% versus 4.5%, P < 0.01). The recurrence rate among those with rebound IoPTH was more than double that of the patients without rebound IoPTH (5.8% versus 2.2%, P = 0.03). Magnitude of rebound, however, did not correlate with recurrence. The rate of persistent disease was not different between those with and without rebound IoPTH. Rebound was a much better indicator of recurrence than patients whose final IoPTH levels were not within the normal range.

Conclusions

Rebound IoPTH is more common in patients who develop recurrent hyperparathyroidism. Therefore, surgeons should closely monitor patients with rebound IoPTH for disease recurrence.     

Natural history of parathyroid function and calcium metabolism after kidney transplantation: a single-centre study.

BACKGROUND: The natural history of parathyroid function after successful renal transplantation (RT) and the factors predisposing to persistent hyperparathyroidism (HPT) are not well established. A better knowledge of these data may be helpful in the development of algorithms for optimal surveillance and treatment of HPT after successful RT. Our aim was to evaluate the post-transplant natural history of parathyroid function and calcium metabolism in patients with a functional renal graft and to identify risk factors for persistent HPT. METHODS: Charts of 1165 allograft kidney recipients transplanted between 1989 and 2000 were reviewed. Patients with an intact parathyroid hormone (iPTH) level available at the time of transplantation were identified. The charts of the latter patients were checked for a variety of demographic and clinical data, and all determinations of the iPTH concentration available since transplantation were recorded. Serum levels of calcium, phosphorus, alkaline phosphatases and creatinine, concurrently determined, were also registered. RESULTS: After an initial fall, iPTH levels showed a slow but steady decline towards the upper normal limit. The prevalence of persistent HPT, defined as an iPTH level > or =2.5 times the upper normal limit or the need for parathyroidectomy following transplantation, remained stable at approximately 17% up to 4 years after transplantation. Patients with persistent HPT had significantly elevated serum levels of iPTH, calcium and phosphorus at the time of RT, and had spent a longer time on dialysis. Post-transplant iPTH levels correlated significantly with transplant kidney function. CONCLUSION: Kidney transplant recipients with a high iPTH and calcium x phosphate product at the time of transplantation are at risk for persistent HPT especially when renal function is suboptimal. Therapy for persistent HPT, if considered, should be initiated 3 months post-transplantation since further spontaneous improvement of parathyroid function thereafter is limited.     

Elevated parathyroid hormone after parathyroidectomy delays symptom improvement

Background

Curative parathyroidectomy for primary hyperparathyroidism (PHPT) resolves various nonspecific symptoms related to the disease. Between 8% and 40% of patients with normocalcemia after parathyroidectomy have persistently elevated parathyroid hormone (ePTH) levels at follow-up. We investigated whether ePTH in the early postoperative period was associated with the timing of symptom improvement.

Materials and methods

This prospective study included adult patients with PHPT who underwent curative parathyroidectomy from November 2011 to September 2012. Biochemical testing at 2 wk postoperatively identified ePTH (defined as PTH > 72 pg/mL) versus normal PTH (nPTH). A questionnaire administered pre- and post-operatively at 6 wk and 6 mo asked patients to rate the frequency of 18 symptoms of PHPT on a five-point Likert scale. Student t-tests were used to compare pre- with postoperative changes in scores for individual symptoms.

Results

Of 194 patients who underwent parathyroidectomy, 129 (66%) participated in the study. Preoperatively, all patients were symptomatic, with a mean of 13 ± 4 symptoms. Two weeks postoperatively, 20 patients (16%) had ePTH. The percentage of patients with postoperative improvement for individual symptoms was compared between groups. At the early time point (6 wk), the ePTH group showed less improvement in 14 of 18 symptoms. This difference reached statistical significance for four symptoms: anxiety, constipation, thirst, and polyuria. By the 6-mo time point, these differences had resolved, and symptom improvement was similar between groups.

Conclusions

ePTH after curative parathyroidectomy may result in a delay in symptom improvement 6 wk postoperatively; however, this difference resolves in 6 mo.     

Direct injections of calcitriol into enlarged parathyroid glands in chronic dialysis patients with severe parathyroid hyperfunction

Summary: Severe secondary hyperparathyroidism in chronic dialysis patients has been recently treated by supraphysiological concentration of calcitriol achieved through pulse therapy. However, there are many patients resistant to this therapy, who usually have larger parathyroid gland(s). to overcome this resistance, calcitriol was injected directly into the enlarged glands under ultrasonographic guidance. We injected 70–90% of the calculated gland volume of calcitriol solution (1 μg/mL) into the glands of 7 patients three times per week for 2 weeks. the parathyroid hormone (PTH) levels decreased significantly after 2 weeks of direct injections of calcitriol. Following a further 4 weeks of calcitriol pulse therapy, PTH levels remained suppressed and serum alkaline phosphatase activity and the volume of parathyroid glands also decreased. During the long-term follow up, five patients remained well controlled with calcitriol pulse therapy, while two patients needed ethanol injections to control hyperparathyroidism. Although we could not completely rule out a toxic effect of the vehicle, direct injection of calcitriol into parathyroid glands may be another treatment option for chronic dialysis patients. Our data further support the important role of resistance of parathyroid cells to calcitriol in the pathogenesis of parathyroid hyper function in uraemic patients.     

Transferrin-mediated uptake of aluminium by human parathyroid cells results in reduced parathyroid hormone secretion.

BACKGROUND: The present study investigates whether aluminium-transferrin (Al-Tf) uptake by Tf receptor-mediated endocytosis induces hypoparathyroidism and thus might contribute to the increasing prevalence of adynamic bone disease (ABD) in the current dialysis population. METHODS AND RESULTS: Human parathyroid glands as well as in vitro cultured human parathyroid cells were shown to express Tf receptors. Five-day-old cultures of parathyroid cells were incubated for 48 h in serum-free DMEM/F12 supplemented with 12 microM apo-Tf: 12 microM Tf to which 150 microg/l Al or 150 microg/l Al-citrate (Al-ci) was bound. The amount of Al taken up by the parathyroid cells either as Al-Tf or Al-ci did not differ. However, incubation of cell cultures with Al-Tf showed a significant proportional decrease (mean+/-SEM, -23.1+/-4.5%) in iPTH secretion as compared to the reference apo-Tf cultures. Al-ci did not suppress PTH secretion (+3.4+/-6.5%). The Al uptake after incubation with Al-Tf was found to be dose-dependent. With regard to iPTH secretion, a tendency toward a dose response relationship was observed. Northern blot analysis of parathyroid cells incubated in 12 microM apo-Tf or 12 microM Al-Tf demonstrated that the PTH mRNA synthesis was unaffected by the Tf-mediated uptake of Al. These observations suggest an effect of Al on PTH release rather than on PTH synthesis. Since the cytoskeleton can play an important role in the release of secretory vesicles, the influence of Al on the structure of actin, beta-tubulin and vimentin was investigated by confocal microscopy. Comparison of cultures incubated with apo-Tf and Al-Tf revealed no difference in the organization of these cytoskeletal proteins in relation to the inhibitory effect of Al-Tf on PTH secretion. CONCLUSION: In summary, data in the present paper demonstrate that the (i) human parathyroid gland/parathyroid cells exhibit Tf receptors; (ii) Al-Tf complex is taken up by the parathyroid gland in a dose-dependent manner; and (iii) uptake of Al by Tf receptor-mediated endocytosis reduces the secretion of PTH but not its synthesis. These in vitro findings allow us to suggest that Tf receptor-mediated uptake of Al might, besides other factors such as vitamin D, high calcium dialysate or CaCO(3) intake, play a role in the development of hypoparathyroidism associated with ABD. The exact mechanism by which Al-Tf suppresses iPTH secretion remains to be elucidated.