Serum intact parathyroid hormone as a predictor of hypocalcaemia after total thyroidectomy

An individual approach to intraoperative parathyroid hormone measurement during total thyroidectomy

PURPOSE

Hypocalcemia is a common complication of thyroidectomy. Measurement of the intraoperative serum parathyroid hormone (PTH) levels became an established technique but it requires further improvements. We aimed to assess intraoperative PTH level testing results against the hypothesis that the PTH assay may be performed almost immediately after thyroid gland removal.

METHODS

A retrospective cohort study. During total thyroidectomy surgery, the patients had PTH levels measured at the cutting time and again immediately after the thyroid gland is removed. Post-operatively, serial total blood calcium levels were obtained twice daily and recorded.

RESULTS

Among 63 enrolled patients, 39 had multinodular goiter, 15 thyroid carcinoma, and nine had Graves' disease. The mean age was 59.8 ± 15.3 years, 43 females. The mean PTH level before surgery was 45.8 ± 22.0 pg/mL. Post-operatively, 11/63 patients developed hypocalcemia with serum calcium levels <8 mg/dL. Four patients with ≥50 % decrease in PTH concentration were normocalcemic a day after surgery and were discharged early. Four patients with ≥70 % PTH decrease were treated accordingly during prolonged hospitalization and did not suffer from permanent hypocalcemia. The cut-off value of 70 % decrease after the gland removal was able to predict postoperative hypocalcemia with a sensitivity of 100 %, specificity 82.9 %, PPV 60.0 % and NPV 100 %.

CONCLUSION

Measurements of intraoperative PTH may not be performed at fixed time intervals but after 1-2 min after removal of the thyroid gland. Defining those not at risk would allow the majority of patients to be waived from post-operative blood calcium testing and safely discharged early after surgery.

Definition and diagnosis of postsurgical hypoparathyroidism after thyroid surgery: meta-analysis

Background

Postsurgical hypoparathyroidism (PH) is the most frequent complication after thyroid surgery. The aim of this systematic review and meta-analysis is to summarize a unifying definition of PH and to elucidate the best possible approach for early detection of PH.

Methods

A systematic review of the literature according to the PICO framework using Embase, PUBMED and the Cochrane library was carried out on 1 December 2021 followed by analysis for risk of bias, data extraction and meta-analysis. All studies addressing the definition of postoperative hypoparathyroidism and/or diagnostic approaches for early detection and diagnosis were included. Case reports, commentaries, non-English articles, book chapters and pilot studies and reviews were excluded.

Results

From 13 704 articles, 188 articles were eligible for inclusion and further analysis. These articles provided heterogeneous definitions of PH. Meta-analysis revealed that postoperative measurements of parathormone (PTH) levels have a higher sensitivity and specificity than intraoperative PTH measurements to predict PH after thyroid surgery. None of the timeframes analysed after surgery within the first postoperative day (POD1) was superior to predict the onset of PH. PTH levels of less than 15 pg/ml and less than 10 pg/ml are both reliable threshold levels to predict the postoperative onset of PH. A relative reduction of mean(s.d.) PTH levels from pre- to postoperative values of 73 (standard deviation 11) per cent may also be predictive for the development of PH. The estimation of calcium levels on POD1 are recommended.

Conclusion

PH is best defined as an undetectable or inappropriately low postoperative PTH level in the context of hypocalcaemia with or without hypocalcaemic symptoms. PTH levels should be measured after surgery within 24 h. Both threshold levels below 10 and 15 pg/ml or relative loss of PTH before/after thyroid surgery are reliable to predict the onset of PH.

Rate of drop in serum calcium as a predictor of hypocalcemic symptoms post total thyroidectomy

The rate of drop in serum calcium post total thyroidectomy is a predictor of hypocalcemic symptoms in adults, after adjusting for other significant covariates.

INTRODUCTION

Test the hypothesis that rate of drop in calcium is a significant and independent predictor of post-operative hypocalcemic symptoms post total thyroidectomy.

METHODS

A retrospective chart review (electronic and hard copy) for 429 patients who underwent total thyroidectomy from January 2011 to December 2016. We collected information on demographics, clinical characteristics, information on surgical intervention, histopathology reports, clinical course, biochemistries, treatments and discharge instructions.

RESULTS

Sixty-one patients (14%) developed post-operative hypocalcemic symptoms. The rate of calcium drop, younger age, female gender, and lower body mass index, and the presence of parathyroid tissue in resected specimen all correlated significantly with the development of symptoms. The rate of drop in serum calcium and the post-operative serum calcium level remained the only significant predictors of symptom development, after adjustment for other significant co-variates. Using a receiver operating characteristics curve, a cutoff rate of calcium drop > 0.083 mg/dl/h, that is 1 mg/dl over 12 h, has a sensitivity of 71% and specificity of 73% for detecting hypocalcemic symptoms.

CONCLUSION

The rate of drop of serum calcium post total thyroidectomy significantly and independently correlated with the development of hypocalcemic symptoms. Patients with a rate of drop < 1 mg/dl/12 h may be considered for earlier discharge and less aggressive management peri-operatively.

Modification, validation and implementation of a protocol for post-thyroidectomy hypocalcaemia

Introduction The management of post-thyroidectomy hypocalcaemia should facilitate early discharge, and reduce risks of hypocalcaemia, readmission and treatment related hypercalcaemia. This paper describes the implementation, evaluation and revision a protocol for the optimal management of this condition. Methods Day 1 parathyroid hormone (PTH) measurements in addition to calcium measurements were commenced following review of the unit's outcomes and literature on post-thyroidectomy hypocalcaemia. Outcomes from a three-year cohort of patients undergoing thyroid surgery helped amend this protocol (revision 1) to reduce biochemical tests, stipulate the need, nature and dose of vitamin D/calcium supplements, and encourage early discharge. This was further validated over seven months to assess compliance, episodes of hyper and/or hypocalcaemia after discharge, readmissions and need for treatment changes. Further revisions were made (revision 2) and implemented. Results The temporary and long-term postoperative hypocalcaemia rates were 29.1% and 3.2% respectively. Repeat calcium measurements on the first day altered management in only 1.4% of cases. The revised protocol was adhered to in 90% of cases. One patient had hypocalcaemia (due to non-compliance) and one had hypercalcaemia. Revision 2 involved reducing the dose of calcium. Conclusions This is a good example of a unit protocol for post-thyroidectomy hypocalcaemia being developed and modified on the basis of the literature and local experience. Day 1 PTH and calcium levels determine the need for treatment and frequency of follow-up visits, facilitate early discharge, reduce risk of over and/or undertreatment, and are good indicators of permanent hypocalcaemia.

Can Parathormon Levels after Ipsilateral Lobectomy Predict Postoperative Hypocalcemia in Patients Undergoing Total Thyroidectomy?

The purpose of this study was to investigate the relationship between the serum parathormone (PTH) levels measured after completion of hemithyroidectomy on the first side during total thyroidectomy and the postoperative hypocalcemia. The patients were divided into two groups, as those who demonstrated a decrease in PTH levels measured after completion of hemithyroidectomy of the first side (Group 1, n = 43) and those who did not demonstrate a decrease in PTH levels (Group 2, n = 24). The serum PTH levels were measured just before the incision (PTHi), when the hemithyroidectomy stage had been completed (PTHht), at the end of the operation (PTHtt), and at the postoperative 24th hour (PTH24hr). The serum total calcium (Ca21) levels were also measured. The median percentage differences in PTHtt levels based on basal PTHi levels of Groups 1 and 2 were -60.6 and -15.7 per cent, respectively, P = 0.001. The frequency of postoperative biochemical hypocalcemia was higher in Group 1, P < 0.05. It was determined that a 10 per cent or higher decrease in PTHht levels in Group 1 could predict biochemical hypocalcemia at the postoperative 24th hour. In conclusions, postoperative hypocalcemia is seen more frequent in patients with a decrease of PTHht during total thyroidectomy. A decrease of 10 per cent in PTHht levels measured after ipsilateral lobectomy and a 62 per cent or higher decrease in PTHtt levels measured in the end of the total thyroidectomy could be helpful for prediction of postoperative hypocalcemia in these patients.

Predictors and risk factors of hypoparathyroidism after total thyroidectomy

BACKGROUND

The aim of this study was to evaluate the risk factors for hypoparathyroidism after total thyroidectomy and to determine whether early postoperative serum levels of calcium and phosphorus could be used to predict its development.

MATERIALS AND METHODS

The study group consisted of 1030 patients who had undergone total thyroidectomy at our institution between March 2008 and July 2014. The clinicopathologic characteristics, indications for the operation, and surgical details of normocalcemic and hypocalcemic patients were compared, and variations in serum calcium and phosphorus levels were measured every day after the operation.

RESULTS

Of the 1030 patients, 291 (28.2%) were found to have transient hypocalcemia and 27 (2.6%) had permanent hypocalcemia. On univariate analysis, younger age (P = 0.001), female gender (P < 0.001), longer operative time (P = 0.009), extent of central neck dissection (CND) (P = 0.003), and malignancy (P = 0.005) were found to be significantly associated with transient hypocalcemia. On multivariate analysis, female gender (P = 0.001), extent of CND (P = 0.017), and the identification of parathyroid gland (PTG) tissue in permanent pathologic sections were significant factors. In addition, the occurrence of postoperative hypocalcemia was correlated with relative changes in serum calcium and phosphorus levels. Patients whose serum calcium levels decreased over 20% on postoperative day 2 were more likely to develop hypoparathyroidism, with 92% specificity.

CONCLUSION

Female gender (P = 0.001), extent of CND (P = 0.014), and PTG in permanent pathologic sections (P = 0.035) were found to be significant factors affecting the development of hypocalcemia. Despite some study limitations, we suggest that the relative changes in the serum levels of calcium (20%) and of phosphorus (40%) on the second postoperative day may be reliable predictors of post-thyroidectomy hypoparathyroidism.

Comparison of Intraoperative versus Postoperative Parathyroid Hormone Levels to Predict Hypocalcemia Earlier after Total Thyroidectomy

OBJECTIVE

To determine differences in the mean parathyroid hormone (PTH) levels for normocalcemic and hypocalcemic total thyroidectomy patients who were tested for PTH during the intraoperative or early postoperative period.

DATA SOURCES

MEDLINE, the Cochrane Database, and other databases from 1960 to 2014 in the English language and specific to humans for relevant articles.

REVIEW METHODS

Studies were included if PTH was obtained within 24 hours of thyroidectomy. Studies were excluded (1) if only a hemithyroidectomy was performed, (2) if means of studied PTH values were not reported in the article, or (3) if the time of the PTH draw fell outside of defined "intraoperative" or "early postoperative" windows. PTH values were divided into 3 groups: preoperative (control group), intraoperative (ie, discharge decisions were based on PTH values drawn in the operating room), and early postoperative (ie, PTH values at 1 to 4 hours after surgery were used as a guide).

RESULTS

The reported means of perioperative PTH levels and percentage of patients who developed hypocalcemia were collected from 14 studies. PTH evaluated at both the intraoperative and early postoperative periods was significantly lower in patients who became hypocalcemic versus patients who remained normocalcemic. There was no significant difference when PTH was measured intraoperatively or early postoperatively.

CONCLUSION

Intraoperative PTH has no significant disadvantage versus early postoperative PTH when used as a clinical guide for discharge after thyroidectomy.

Clinicopathological risk factors and biochemical predictors of safe discharge after total thyroidectomy and central compartment node dissection for thyroid cancer: a prospective study

To determine the clinicopathological risk factors and reliable biochemical predictors of the development of hypocalcemic symptoms after total thyroidectomy on the basis of serum calcium and intact parathyroid hormone (PTH) levels measured 1 hour after surgery, a prospective study was performed on 817 patients who underwent a total thyroidectomy with central compartment node dissection (CCND) due to well-differentiated thyroid cancer. We evaluated the correlations between hypocalcemic symptom development and clinicopathological factors. And the predictability for hypocalcemic symptom development of intact PTH cut-offs (<10 pg/mL and <20 pg/mL, resp.) according to serum calcium level subgroup was analyzed. Female gender (P < 0.001) was the only independent risk factor for hypocalcemic symptom development in multivariate regression analysis. The negative predictive value (NPV) of intact PTH, signifying nondevelopment of hypocalcemic symptoms, was higher than the positive predictive value (PPV) which signified development of hypocalcemic symptoms. In addition, when we applied the different adoption of the intact PTH cut-off according to serum calcium level, we could obtain more increased NPVs. A female gender and the application of more specific cut-offs for intact PTH according to the serum calcium levels measured 1 hour after surgery may help the patients to be more safely discharged.

Systematic review and meta-analysis of predictors of post-thyroidectomy hypocalcaemia

BACKGROUND

Hypocalcaemia is common after thyroidectomy. Accurate prediction and appropriate management may help reduce morbidity and hospital stay. The aim of this study was to perform a systematic literature review and meta-analysis of predictors of post-thyroidectomy hypocalcaemia.

METHODS

A systematic search of PubMed, EMBASE and the Cochrane Library databases was undertaken, and the quality of manuscripts assessed using a modified Newcastle-Ottawa Scale.

RESULTS

Some 115 observational studies were included. The median (i.q.r.) incidence of transient and permanent hypocalcaemia was 27 (19-38) and 1 (0-3) per cent respectively. Independent predictors of transient hypocalcaemia included levels of preoperative calcium, perioperative parathyroid hormone (PTH), preoperative 25-hydroxyvitamin D and postoperative magnesium. Clinical predictors included surgery for recurrent goitre and reoperation for bleeding. A calcium level lower than 1·88 mmol/l at 24 h after surgery, identification of fewer than two parathyroid glands (PTGs) at surgery, reoperation for bleeding, Graves' disease and heavier thyroid specimens were identified as independent predictors of permanent hypocalcaemia in multivariable analysis. Factors associated with transient hypocalcaemia in meta-analyses were inadvertent PTG excision (odds ratio (OR) 1·90, 95 per cent confidence interval 1·31 to 2·74), PTG autotransplantation (OR 2·03, 1·44 to 2·86), Graves' disease (OR 1·75, 1·34 to 2·28) and female sex (OR 2·28, 1·53 to 3·40).

CONCLUSION

Perioperative PTH, preoperative vitamin D and postoperative changes in calcium are biochemical predictors of post-thyroidectomy hypocalcaemia. Clinical predictors include female sex, Graves' disease, need for parathyroid autotransplantation and inadvertent excision of PTGs.

Predicting the need for calcium and calcitriol supplementation after total thyroidectomy: results of a prospective, randomized study

BACKGROUND

The optimal protocol for the detection and treatment of postthyroidectomy hypoparathyroidism is unknown. We sought to identify and treat patients at risk for symptomatic hypocalcemia on the basis of a single parathyroid hormone (PTH) obtained the morning after surgery (POD1).

METHODS

We performed a prospective, randomized study of total thyroidectomy patients who had POD1 calcium and PTH (pg/mL) levels. Randomization was determined by POD1 PTH: if ≥ 10, patients received no supplementation unless symptomatic; if <10, patients were randomized to calcium, calcium and calcitriol, or no supplementation.

RESULTS

Of 143 patients, 112 (78%) had a POD1 PTH ≥ 10. Hypocalcemic symptoms were transiently reported in 11 (10%) and managed with outpatient calcium. Of 31 patients with PTH <10, 15 (48%) developed symptoms, including 5 who required intravenous calcium. On multivariate logistic regression analysis, when we adjusted for postoperative calcium level and performance of central neck dissection, we found that predictors of hypocalcemic symptoms were younger age (odds ratio 1.59, 95% confidence interval 1.07-2.32) and a PTH <10 (odds ratio 1.08, 95% confidence interval 1.04-1.12). There were no patient or treatment-related factors that predicted a POD1 PTH <10.

CONCLUSION

A single POD1 PTH level <10 can accurately identify those patients at risk for clinically significant hypocalcemia. All total thyroidectomy patients with a postoperative PTH ≥ 10 can be safely discharged without supplementation. Given the small number of patients with PTH <10, it is unclear whether both calcium and calcitriol are needed for these higher-risk patients.

A prospective evaluation of quick intraoperative parathyroid hormone assay at the time of skin closure in predicting clinically relevant hypocalcemia after thyroidectomy

Background

Post-thyroidectomy hypocalcemia is a major contributing factor in delayed hospital discharge and dissuading surgeons from ambulatory thyroidectomy. We prospectively evaluated the accuracy and reliability of quick parathyroid hormone level measurement at skin closure (PTH-SC) in predicting clinically relevant hypocalcemia (i.e., patients requiring calcium ± calcitriol supplements on hospital discharge).

Methods

Of the 117 patients who underwent a total or completion total thyroidectomy and PTH-SC, 17 (14.5 %) had hypocalcemic symptoms or adjusted calcium <1.90 mmol/L requiring calcium and/or calcitriol supplements on discharge. Serum calcium was checked regularly in the perioperative period until stabilization and an additional quick PTH was checked on the following morning (PTH-D1). Univariate and multivariate analyses were performed to evaluate potential preoperative clinicopathologic factors and postoperative day 0 biochemical indicators. Youden’s index and the area under the ROC curve (AUC) were used to determine the best cutoff value and predictability of significant variables or criteria, respectively.

Results

In the multivariate analysis, low preoperative adjusted calcium (p = 0.041) and low PTH-SC (p = 0.001) were the two independent variables associated with hypocalcemia. PTH-SC (≤1 or >1 pmol/L) had a higher specificity (95.0 %) and AUC (0.887) than serial calcium monitoring or PTH-D1 alone. Although 3/98 of patients with PTH-SC >1 pmol/L required calcium supplements on discharge, they required only the minimum amount to maintain normocalcemia.

Conclusion

PTH-SC is an accurate and reliable means of predicting clinically relevant hypocalcemia. It would be reasonable to discharge those with PTH-SC >1 pmol/L on the same operative day as the risk of life-threatening hypocalcemia would seem unlikely.

Applicability of imediate, late or serial intact parathyroid hormone measurement following total thyroidectomy

Hypocalcemia is the most common complication after total thyroidectomy. Intact parathyroid hormone (i-PTH) testing is a proven effective method to detect patients at risk for postoperative symptomatic hypocalcemia. However, there is still uncertainty as to the timing of i-PTH testing in a clinical setting.

Objective

This study looked into the correlation between serum i-PTH levels measured at different times after total thyroidectomy and the risk of symptomatic hypocalcemia.

Methods

This retrospective case series studied a group of 110 consecutive for hypocalcemia and intact parathyroid hormone (PTHi) levels four and twelve hours following total thyroidectomy. Statistical analysis was used to evaluate the performance of isolated and serial i-PTH measurements to determine the likelihood of symptomatic hypocalcemia.

Results

I-PTH is highly sensitive (90.3%-96.8%) and specific (77.2%-87.3%) for symptomatic hypocalcemia. There was no significant difference in the sensitivity levels of the tests done four and twelve hours after surgery or in a serial fashion. However, the 12-hour i-PTH level was more specific (p < 0.0007).

Conclusion

Single i-PTH testing done 12 hours after total thyroidectomy may be used as a screening test to detect patients at risk for symptomatic hypocalcemia.

Parathyroid hormone: an early predictor of symptomatic hypocalcemia after total thyroidectomy

OBJECTIVE: The purpose of this study was to evaluate if the measurement of peri-operative parathyroid hormone (PTH) is able to identify patients with increased risk of developing symptoms of hypocalcemia. SUBJECTS AND METHODS: Forty patients who underwent total thyroidectomy were studied prospectively. Ionized serum calcium and PTH were measured after induction of anesthesia, one hour (PTH1) and one day after surgery (PTH24). Patients were evaluated for symptoms of hypocalcemia and treated with calcium and vitamin D supplementation as necessary. RESULTS: Symptomatic hypocalcemia developed in 16 patients. Symptomatic patients had significant lower PTH1 and greater drops in PTH levels. The selection of 12.1 ng/L as PTH1 level cutoff level divided patients with and without symptoms with 93.7% sensitivity and 91.6% specificity. The selection of 73.5% as the cutoff value for PTH decrease resulted in 91.6% sensitivity and 87.5% specificity. CONCLUSION: PTH1 levels and the drop in PTH levels are reliable predictors of developing symptomatic hypocalcemia after total thyroidectomy.

To supplement or not to supplement: a cost-utility analysis of calcium and vitamin D repletion in patients after thyroidectomy

BACKGROUND

Postoperative hypocalcemia is the most common complication after thyroidectomy; prevention and treatment remain areas of ongoing debate. The purpose of this study was to determine the incremental cost utility of routine versus selective calcium and vitamin D supplementation after total or completion thyroidectomy.

METHODS

A cost-utility analysis using a Markov decision model was performed for a hypothetical cohort of adult patients after thyroidectomy. Routine or selective supplementation of oral calcium carbonate, vitamin D (calcitriol), and intravenous calcium gluconate, when required, was used. Selective supplementation was determined by serum intact parathyroid hormone levels. The incremental cost utility, measured in U.S. dollars per quality-adjusted life-year (QALY), was calculated.

RESULTS

In the base-case analysis, the cost of routine supplementation was $102 versus $164 for selective supplementation. Patients in the routine arm gained 0.002 QALYs compared to patients in the selective arm (0.95936 QALYs vs. 0.95725 QALYs). At the population level, this translates into a savings of $29,365/QALY (95% confidence interval, -$66,650 to -$1,772) for routine supplementation. Sensitivity analyses demonstrated that the model was most sensitive to the utility of the hypocalcemic state, postoperative rates of hypocalcemia, and cost of serum parathyroid hormone testing.

CONCLUSIONS

Routine oral calcium and calcitriol supplementation in patients after thyroidectomy seems to be less expensive and results in higher patient utility than selective supplementation. Surgeons who have very low rates of hypocalcemia in their patients may benefit less from routine supplementation.

Prediction of hypocalcemia after using 1- to 6-hour postoperative parathyroid hormone and calcium levels: an analysis of pooled individual patient data from 3 observational studies

BACKGROUND

Parathyroid hormone (PTH) levels up to 6 hours postthyroidectomy have been shown to have excellent predictive power in determining hypocalcemia. In this study, we investigate the usefulness of combining calcium and PTH to increase the predictive power.

METHODS

Individual patient data were obtained from 3 studies (152 patients) that fulfilled our criteria (using PTH assay within hours postthyroidectomy to predict symptomatic hypocalcemia).

RESULTS

Changes in combined PTH and calcium threshold levels checked 1 to 6 hours after thyroidectomy were excellent in predicting postoperative hypocalcemia. A decrease in PTH of 60%, coupled with a simultaneous decrease in calcium of 10%, 5 to 6 hours postoperatively resulted in a sensitivity and specificity of 100%. However, combined PTH and calcium threshold changes were not significantly better than using PTH threshold changes alone.

CONCLUSIONS

Threshold changes in serum calcium and PTH, checked hours after surgery, can be used together to accurately predict whether a patient will become hypocalcemic after thyroidectomy.

Hypocalcemia after Thyroidectomy: The Need for Improved Definitions

Introduction

Hypocalcemia and permanent hypoparathyroidism are important outcome measures after total thyroidectomy. The aim of this article is to identify and highlight the wide variation in the adequacy/definition of these complications as reported in the surgical literature.

Methods

Nineteen journal articles (2008) on complications of thyroidectomy and 17 journal articles (2002) on ‘prediction’ of postthyroidectomy hypocalcemia derived from a PubMed search were reviewed.

Results

Only 21% of studies of describing outcome and complications of thyroidectomy defined hypocalcemia, temporary/permanent hypoparathyroidism. 47% of studies on the early prediction of hypocalcemia failed to quote their normal range of serum calcium. When stated, the biochemical definition of hypocalcemia varied from 1.8 to 2.12 mmol/l. There is no consistent definition of post-thyroidectomy hypoparathyroidism.

Conclusion

There is no consensus apparent on literature review as to what constitutes post-thyroidectomy hypocalcemia and hypoparathyroidism. The need to benchmark and define appropriate outcome measures of thyroid surgery demands that this deficit is addressed.

Postoperative hypoparathyroidism: medical and surgical therapeutic options

BACKGROUND

Hypoparathyroidism occurs when the parathyroid glands, through lack of secretion of or resistance to parathyroid hormone (PTH), are unable to maintain calcium homeostasis. Transient and permanent hypoparathyroidism are most commonly seen as complications of neck surgery, resulting from devascularization of the parathyroids, unintentional resection, or accidental coagulation of the parathyroids.

SUMMARY

Although strategies for treatment of transient and permanent hypoparathyroidism differ, the classical approach involves supplementation with calcium and vitamin D or its analogues with the major goal of achieving low normal serum calcium and normal serum phosphorus. There are a variety of calcium and vitamin D preparations available for use in the treatment of symptomatic hypoparathyroidism. In selecting the appropriate vitamin D sterol for treatment, it is important to consider the pharmocodynamics, the potency at the tissue level, the rapidity of action, and ease of reversal of toxicity. Drawbacks to conventional therapy, including narrow therapeutic window and propensity for hypercalciuria and hypercalcemia, have prompted investigation into alternatives, namely PTH replacement and parathyroid gland autotransplantation.

CONCLUSION

Long-term supplementation with vitamin D or its analogues and oral calcium is the mainstay of management of postoperative hypoparathyroidism; however, PTH replacement strategies with either PTH or parathyroid gland autotransplantation are emerging as alternative strategies to avoid the complications of conventional therapy.

Evidence for the role of perioperative PTH measurement after total thyroidectomy as a predictor of hypocalcemia

BACKGROUND

Total thyroidectomy is now accepted worldwide as the standard surgical procedure for the management of benign bilateral nodular thyroid disease. Hypocalcemia is the most common complication of that procedure and a variety of strategies for diagnosing and managing post-thyroidectomy hypocalcemia have been advocated. Increasingly, the use of intact parathyroid hormone (PTH) has been utilized to try to predict those patients at risk of developing post-thyroidectomy hypocalcemia.

METHODS

A Medline search of English language literature was performed and we reviewed the evidence in relation to the following three issues: the accuracy of PTH in predicting hypocalcemia, the optimal timing for measuring PTH, and the routine use of oral calcium supplements.

RESULTS

Post-thyroidectomy PTH levels accurately predict hypocalcemia but lack 100% accuracy. Progressive and severe hypocalcemia is unlikely in the setting of a normal PTH level and hence PTH can be cautiously used to facilitate discharge within 24 h for many patients. In addition, PTH levels can be used to implement early treatment with calcium and/or vitamin D supplements to reduce the incidence and severity of hypocalcemia. A single PTH measurement taken any time from 10 min to several hours postoperative will provide equally accurate results for predicting post-thyroidectomy hypocalcemia. Routine use of oral calcium supplements may reduce the incidence and severity of post-thyroidectomy hypocalcemia.

CONCLUSION

Postoperative PTH can be used to stratify the risk of patients developing hypocalcemia after thyroidectomy. In addition, the routine use of oral calcium supplements can lead to decreased incidence and severity of post-thyroidectomy hypocalcemia. Protocols based on PTH and the routine use of oral calcium supplements can lead to improved patient outcomes after thyroidectomy.

Kinetics of serum parathyroid hormone during and after thyroid surgery

Background

Hypocalcaemia after thyroidectomy is thought to result from surgical damage to the parathyroid glands. This study analysed postoperative outcomes related to perioperative parathyroid hormone (PTH) levels.

Methods

Some 402 consecutive patients undergoing thyroid surgery were studied prospectively to monitor perioperative changes in serum PTH and Ca2+ levels, and clinical symptoms of hypocalcaemia.

Results

Transient symptomatic hypocalcaemia and persistent hypoparathyroidism occurred in 61 (15 per cent) and six (1·5 per cent) of 402 patients respectively. The intraoperative decline in PTH was 20·2 per cent; the trough (63·8 per cent of preoperative value) was reached 3 h after surgery. Before surgery, PTH levels were correlated inversely with serum Ca2+ concentration. The correlation remained positive from 3 h after surgery until postoperative day 14. Thus, PTH secretion was reduced, but remained sufficient to prevent symptomatic hypocalcaemia in most patients. A low serum PTH level was predictive of persistent hypoparathyroidism (sensitivity and negative predictive value 100 per cent, but poor specificity of 54·1 per cent).

Conclusion

Thyroid surgery impairs hormone secretion by the parathyroid glands resulting in postoperative latent parathyroid insufficiency. Normal PTH levels 3 h after surgery and a normal serum calcium level on the first postoperative day rule out persistent hypoparathyroidism.

Early Postoperative PTH Levels as a Predictor of Hypocalcaemia and Facilitating Safe Early Discharge After Total Thyroidectomy

OBJECTIVE

Hypocalcaemia after total or completion thyroidectomy has traditionally required 48 hours or longer inpatient monitoring of serum calcium levels. The use of parathyroid hormone (PTH) levels to predict postoperative hypocalcaemia is well established. This study aimed to measure the impact of a management plan based on postoperative PTH on achieving safe early discharge after thyroidectomy.

METHODS

A prospective cohort study of 76 patients undergoing total or completion thyroidectomy was performed. Serum PTH level was measured 4-12 hours postoperatively and used to stratify patients into three groups: normal PTH (> 12 pg/mL), undetectable PTH (< 3 pg/mL) and intermediate PTH (4-11 pg/mL). A subgroup analysis was performed on a cohort of patients after a change in the management philosophy aiming for day 1 discharge based on the postoperative PTH.

RESULTS

Seventy-five percent of eligible patients were successfully discharged on day 1 with no complications or readmissions; 21% of patients had intermediate or undetectable PTH levels and were monitored for 48 hours. No patient required intravenous calcium and no patient suffered permanent hypoparathyroidism.

CONCLUSION

A single PTH measurement at 4-12 hours postoperatively allows for accurate prediction of patients at risk of hypocalcaemia. Patients with a normal postoperative PTH level can be safely discharged on the first postoperative day.

AUSTRALIAN ENDOCRINE SURGEONS GUIDELINES AES06/01. POSTOPERATIVE PARATHYROID HORMONE MEASUREMENT AND EARLY DISCHARGE AFTER TOTAL THYROIDECTOMY: ANALYSIS OF AUSTRALIAN DATA AND MANAGEMENT RECOMMENDATIONS

BACKGROUND

The risk of hypocalcaemia after thyroidectomy has traditionally mandated inpatient monitoring for signs and symptoms as well as frequent measurement of serum calcium levels. In recent years there has been much interest in the published work about the use of intact parathyroid hormone (PTH) to better predict hypocalcaemia after thyroidectomy. Although generally accurate, the use of intact parathyroid hormone in Australia has not become widespread. On behalf of the Australian Endocrine Surgeons an analysis of Australian data on the use of PTH levels to predict hypocalcaemia after thyroidectomy was carried out. The data were analysed with a view to making recommendations about the use of this test in clinical practice and the feasibility of achieving safe early discharge for patients.

METHODS

Four recently published or presented Australian studies on the use of early postoperative PTH levels after total or completion thyroidectomy to predict post-thyroidectomy hypocalcaemia were analysed. Patients were stratified into either normal or low PTH groups as defined by the normal ranges set by each laboratory and rates of hypocalcaemia were analysed.

RESULTS

A total of 458 patients were examined. Seventy-six per cent of the patients had PTH in the normal range and hypocalcaemia (serum-corrected calcium cCa(2+) < 2.00 mmol/L) occurred in 17.9% of patients. Sensitivity, specificity and positive predictive values of a normal postoperative PTH level as a predictor of normocalcaemia are 92.6, 70.7 and 92.3%, respectively. Low PTH as a predictor of hypocalcaemia is poor. The overall sensitivity, specificity and positive predictive values are 70.7, 92.6 and 71.6%, respectively.

CONCLUSION

Normal postoperative PTH levels accurately predict normocalcaemia after total or completion thyroidectomy. PTH levels should ideally be drawn 4 h postoperatively and patients with PTH in the normal range can be safely discharged on the first postoperative day. Use of oral calcium supplements, either as needed or routinely, will avoid mild symptoms that may develop in 7% without treatment.

Parathyroid hormone levels 4 hours after surgery do not accurately predict post-thyroidectomy hypocalcemia

BACKGROUND

We evaluated the reliability of intact parathyroid hormone (iPTH) levels 4 hours after thyroidectomy (4h-iPTH) as a predictor of hypocalcemia in a large series of patients.

METHODS

A prospective experimental design involving 523 consecutive patients between September 1, 2004, and June 30, 2005, was employed. The specificity, sensitivity, and overall accuracy of 4h-iPTH in predicting post-thyroidectomy hypocalcemia and symptoms were determined.

RESULTS

A total of 199 patients developed hypocalcemia (serum calcium concentrations <8.0 mg/dl). Five patients still were receiving vitamin D/oral calcium at 6 months after the operation. Seventy-three patients experienced mild symptoms. The 4h-iPTH levels were reduced in hypocalcemic patients (28.8 +/- 15.3 vs 11.2 +/- 11.6 pg/ml) (P < .001). The 4h-iPTH levels were within the normal range (10 to 65 pg/ml) in 360 patients (290 normocalcemic) and subnormal in 163 patients (129 hypocalcemic, of whom 62 were symptomatic). The accuracy of 4h-iPTH levels <10 pg/ml in predicting post-thyroidectomy hypocalcemia and symptoms was 80.1% and 78.6%, respectively. False-negative results were observed in 70 hypocalcemic patients (13.4%), 11 of whom were symptomatic (2.1%).

CONCLUSIONS

Subnormal 4h-iPTH levels alone did not accurately predict clinically relevant postoperative hypocalcemia. The optimal cut-off level and its integration with preoperative and postoperative serum calcium concentrations should be reconsidered.