Hypocalcemia after Total Thyroidectomy in Graves Disease

Artificial neural network to predict post-operative hypocalcemia following total thyroidectomy

The primary objective of this study was to use artificial neural network (ANN) to predict the post operative hypocalcemia and severity of hypocalcemia following total thyroidectomy. The secondary objective was to determine the weightage for the factors predicting the hypocalcemia with the ANN. A single center, retrospective case series included treatment-naive patients undergoing total thyroidectomy for benign or malignant thyroid nodules from January 2020 to December 2022. Artificial neural network (ANN) - Multilayer Perceptron (MLP) used to predict post-operative hypocalcemia in ANN. Multivariate analysis was used construct validity. The data of 196 total thyroidectomy cases was used for training and testing. The mean incorrect prediction during training and testing was 3.18% (± σ = 0.65%) and 3.66% (± σ = 1.88%) for hypocalcemia. The cumulative Root-Mean-Square-Error (RMSE) for MLP model was 0.29 (± σ = 0.02) and 0.32 (± σ = 0.04) for training and testing, respectively. Area under ROC was 0.98 for predicting hypocalcemia 0.942 for predicting the severity of hypocalcemia. Multivariate analysis showed lower levels of post operative parathormone levels to be predictor of hypocalcemia (p < 0.01). The maximum weightage given to iPTH (100%) > Need for sternotomy (28.55%). Our MLP NN model predicted the post-operative hypocalcemia in 96.8% of training samples and 96.3% of testing samples, and severity in 92.8% of testing sample in 10 generations. however, it must be used with caution and always in conjunction with the expertise of the surgical team. Level of Evidence - 3b.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-024-04608-9.

A prospective cross-sectional study on hypocalcemia after total thyroidectomy in patients with Graves' disease: insights on secondary hyperparathyroidism

PURPOSE

To investigate the parathyroid function and calcium (Ca) levels in the secondary hyperparathyroidism (SHPT) state in patients with Graves' disease.

METHODS

We examined 31 consecutive patients with Graves' disease without chronic kidney disease, who were treated with total thyroidectomy. The patients were divided into a normal parathyroid hormone (PTH) group (NPTH group; n = 19) with a PTH level ≤ 65 pg/mL, and a secondary hyperparathyroidism group (SHPT group; n = 12), with a PTH level > 65 pg/mL. The PTH and Ca-related parameters were examined and the risk factors for postoperative hypocalcemia were analyzed.

RESULTS

The preoperative Ca level was significantly lower (2.24 ± 0.06 vs. 2.31 ± 0.07 mmol/L, p < 0.05) in the SHPT group than in the NPTH group. The reduction in PTH, 1,25-dihydroxyvitamin D (1,25(OH)2D), and Ca levels from the preoperative day to the next morning was significantly greater in the SHPT group than in the NPTH group (p < 0.05). When intraoperative factors were included, the decrease in the PTH level alone was significant. SHPT was a significant factor in determining the extent of PTH reduction.

CONCLUSIONS

Hyperfunctioning parathyroid glands in the SHPT state were more susceptible to postoperative PTH reduction, which, combined with low preoperative Ca levels, increased the risk of postoperative hypocalcemia in patients with Graves' disease.

A Study of Incidence and Management of Postoperative Hypocalcemia in Patients Undergoing Near-Total and Total Thyroidectomy

To study the incidence and management of postoperative hypocalcemia in participants undergoing near-total (NTT) and total thyroidectomy (TT) at a tertiary health care center. This is an observational prospective study. Patients posted for NTT and TT in our institute and meeting the inclusion criteria were included. A total of 45 participants were enrolled. The serum calcium was measured on postoperative day 2, at the time of discharge and on 3 months follow-up. A combination of injectable and oral calcium supplements with or without vitamin D sachet was used for the treatment of hypocalcemia. Hypocalcemia was observed in 49% cases. Women were observed to develop hypocalcemia at a higher rate than men. Incidence of hypocalcemia was more in TT patients than NTT patients. Cases with malignant pathology were more susceptible to develop hypocalcemia than those with benign pathology. Operated TT with concomitant neck dissection were at higher risk for development of hypocalcemia. There was no significant association between age and incidence of hypocalcemia. Serum calcium measured on postoperative day 2 was a reliable indicator of risk of hypocalcemia. The early measurement of serum calcium level is a reliable indicator of the risk of hypocalcemia. Standardized treatment of hypocalcemic patients with calcium and vitamin D supplements can reduce the incidence and morbidity associated with postoperative hypocalcemia.

Development of a tool to calculate the probability of hypocalcemia after total thyroidectomy: a prospective study

PURPOSE

This study aimed to evaluate the ability of the percentage of decrease in serum PTH level in the first 8 h after total thyroidectomy (TT) to predict hypocalcemia requiring Ca supplementation and develop a tool to predict it.

METHODS

97 patients who underwent TT with measurement of preoperative parathyroid hormone (PTH) levels were prospectively evaluated 1 and 8 h after TT; postoperative magnesium (Mg2PO) and phosphorus levels were evaluated on the 2nd day after surgery. The percentage of decrease in PTH level 1 h (%dPTH1h) and 8 h (%dPTH8h) postoperatively and predictors of hypocalcemia requiring Ca supplementation were evaluated and an equation was developed to predict this outcome.

RESULTS

%dPTH1h (p = 0.002), %dPTH8h (p = 0.001) and (Mg2PO) (p < 0.01) were isolated predictors of postoperative hypocalcemia requiring Ca supplementation. The data obtained led to the development of two tools to predict this complication.

CONCLUSIONS

The percentage of decrease in PTH level 1 h and 8 h postoperatively and the magnesium level on the 2nd day after surgery were predictors of more severe hypocalcemia, and an auxiliary tool for predicting this complication was developed.

Comparison of Perioperative Outcomes in Patients with Graves' Disease Undergoing Total Thyroidectomy With or Without Near Infrared Autofluorescence Imaging

Background: The impact of near-infrared autofluorescence (NIRAF) imaging on postthyroidectomy hypocalcemia is controversial. As patients with Graves' disease are at increased risk, our aim was to compare postoperative parathyroid function in these patients undergoing total thyroidectomy (TT) with or without NIRAF imaging. Methods: This was a retrospective "before and after" study, comparing outcomes of patients who underwent TT without or with NIRAF imaging at a single center. Primary outcome was the incidence of temporary hypocalcemia and secondary outcomes, rates of incidental parathyroidectomy on final specimens and permanent hypocalcemia. Analyses were performed using Mann-Whitney U and chi-Square tests. Continuous data are expressed as median (interquartile range). Results: There were 85 patients in NIRAF and 100 patients in non-NIRAF group. Groups were comparable regarding age, gender, body-mass index, and thyroid weight. Number of parathyroid glands identified intraoperatively was 3 in both groups (p = 0.47). Intraoperative parathyroid implantation rate was 16.5% in NIRAF and 6% in non-NIRAF group (p = 0.02). Incidental parathyroidectomy rate on final pathology was 12.9% in NIRAF and 32% in non-NIRAF group (p = 0.002). The rates of temporary (11.7% vs. 16%) and permanent hypocalcemia (2.4% vs. 2%) were similar between the two groups, respectively (p = 0.66). Conclusion: To our knowledge, this is the first comparative study investigating the impact of NIRAF on postoperative parathyroid function after thyroidectomy for Graves' disease. The rate of incidental parathyroidectomy on final pathology was lower with use of NIRAF, without an impact on temporary or permanent hypocalcemia rates compared to conventional technique.

Frequency and Risk Factors of Permanent Hypoparathyroidism After Total Thyroidectomy: An Experience at a Tertiary Care Hospital in Pakistan

OBJECTIVES

Thyroid surgeries are among the most common operations performed in the world. Hypocalcemia following total thyroidectomy (TT) is a common complication that is sometimes difficult to correct. This study aims to determine the frequency of hypocalcemia and permanent hypoparathyroidism (PtHPT) following TT.

METHODS

A total of 363 patient records were reviewed who underwent TT for any reason. Thirty-eight patients did not have a follow-up in the clinic in the postoperative period and were excluded from the final analysis with the final sample as 325. For patients who developed hypocalcemia during the postoperative hospital stay, their lowest calcium levels were recorded and medical records were reviewed for the period of one year for the requirement of oral calcium and active form of vitamin D (calcitriol or alpha calcidiol) in the outpatient setting. Patients who required calcium and vitamin D supplementation for up to 1 year were labeled as having PtHPT. Risk factors were analyzed among those who developed PtHPT.

RESULTS

From a total of 325 patients postoperative hypocalcemia developed in 163 (50.2%) patients, and 162 (49.8%) patients remained normocalcemic. Permanent hypoparathyroidism was found in 42(12.9%) patients and transient HPT in 121 (37.2%). Age, severe postoperative hypocalcemia (PoHC), and readmission for hypocalcemia were independent risk factors for PtHPT.

CONCLUSIONS

Transient hypoparathyroidism (THPT) is common in our setup. Patients who develop severe hypocalcemia postoperatively and need readmission should be closely followed for the development of PtHPT.

Postoperative Hypocalcemia in Hyperthyroid Patients: The Parathyroids Aren't Always to Blame

INTRODUCTION

Hypocalcemia is commonly reported after thyroidectomy and has multiple possible etiologies including: parathyroid devascularization, reactive hypoparathyroidism from relative hypercalcemia in thyrotoxicosis, and abrupt reversal of thyrotoxic osteodystrophy. In patients that are actively hyperthyroid and undergoing thyroidectomy, it is not known how many experience hypocalcemia from nonhypoparathyroidism etiologies. Therefore, our aim was to examine the relationship among thyrotoxicosis, hypocalcemia, and hypoparathyroidism.

METHODS

A retrospective review was performed of prospectively-collected data from all patients undergoing thyroidectomy for hyperthyroidism by 4 surgeons from 2016 to 2020. All patients carried a diagnosis of Graves' disease or toxic multinodular goiter. Patient demographics, preoperative medications, laboratory reports, and postoperative medications were reviewed. Hypocalcemia within the first month of surgery despite a normal parathyroid hormone (PTH) level was the primary outcome of interest and was compared between patients with and without thyrotoxicosis. Secondary outcomes were duration of postoperative calcium use and the relationship between preoperative calcium supplementation and postoperative calcium supplementation. Descriptive statistics, Wilcoxon rank-sum, and chi-square tests were used for bivariate analysis, as appropriate.

RESULTS

A total of 191 patients were identified, with mean age of 40.5 y (range 6-86). Most patients were female (80%) and had Graves' disease (80%). At the time of surgery, 116 (61%) had uncontrolled hyperthyroidism (thyrotoxic group, Free Thyroxine >1.64 ng/dL or Free Triiodothyronine > 4.4 ng/dL), with the remaining 75 (39%) considered euthyroid. Postoperative hypocalcemia (calcium < 8.4 mg/dL) developed in 27 (14%), while hypoparathyroidism (PTH < 12 pg/mL) was observed in 39 (26%). Thyrotoxic patients comprised a majority of those with hypocalcemia (n = 22, 81%, P = 0.01) and hypoparathyroidism immediately following surgery (n = 14, 77%, P = 0.04). However, a majority of initially hypocalcemic, thyrotoxic patients had normal PTH values within the first month after surgery (n = 17, 85%), pointing to a potential nonparathyroid etiology. On bivariate analysis, no significant relationship was found for thyrotoxic patients with initial postoperative hypocalcemia (18%) and hypoparathyroidism <1-month after surgery (29%, P = 0.29) or between 1 and 6 mo after surgery (2%, P = 0.24). Of the 19 patients in the nonhypoparathyroidism group, 17 (89%) were off all calcium supplements by 6 mo postop.

CONCLUSIONS

In patients with hyperthyroidism, those in active thyrotoxicosis at time of surgery have a higher rate of postoperative hypocalcemia compared to euthyroid patients. When hypocalcemia lasts >1 mo postoperatively, data from this study suggest that hypoparathyroidism may not be the primary etiology in many of these patients, who typically require calcium supplementation no more than 6 mo postoperatively.

Etiology and Pathophysiology of Hypoparathyroidism: A Narrative Review

The approach utilized a systematic review of the medical literature executed with specifically designed criteria that focused on the etiologies and pathogenesis of hypoparathyroidism. Enhanced attention by endocrine surgeons to new knowledge about parathyroid gland viability are reviewed along with the role of intraoperative parathyroid hormone (ioPTH) monitoring during and after neck surgery. Nonsurgical etiologies account for a significant proportion of cases of hypoparathyroidism (~25%), and among them, genetic etiologies are key. Given the pervasive nature of PTH deficiency across multiple organ systems, a detailed review of the skeletal, renal, neuromuscular, and ocular complications is provided. The burden of illness on affected patients and their caregivers contributes to reduced quality of life and social costs for this chronic endocrinopathy. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Preoperative vitamin D deficiency is associated with increased risk of postoperative hypocalcemia after total thyroidectomy

Prior single-institution studies suggest that preoperative vitamin D deficiency (VDD) is associated with postoperative hypocalcemia and a prolonged length of hospital stay following total thyroidectomy. In this study, we employ a multi-institutional, de-identified electronic health records database to address this issue. We hypothesize that total thyroidectomy patients with preoperative VDD will be at an increased associated risk of postoperative hypocalcemia and hospitalization. Using Cerner Health Facts, we identified 2447 patients who underwent total or subtotal thyroidectomy between 2008 and 2016 and who had a documented 25-hydroxyvitamin D concentration obtained within 12 months of the surgery date using International Classification of Diseases 9/10, Current Procedural Terminology and Healthcare Common Procedure Coding System codes. Data from 984 patients who underwent total thyroidectomy were analyzed. Analysis of variance models estimated the effect of VDD on postoperative numerical variables. Multiple logistic regression estimated the risk of postoperative hypocalcemia and hospital stay, adjusting for any imbalanced demographic variables and operative characteristics. On average, postoperative total calcium concentrations in the VDD group were lower by 0.3 mg/dL compared with that of the non-VDD group (p<0.01). The risk of postoperative hypocalcemia was 2.2 times higher in the VDD group compared with the non-VDD group (p<0.01). Although the length of hospital stay after thyroidectomy was longer in the VDD group compared with the non-VDD group (p=0.03), VDD is not an independent risk factor for prolonged hospitalization following thyroidectomy (p=0.13). VDD is associated with a higher risk of hypocalcemia following total thyroidectomy. Prethyroidectomy operative screening for VDD should be considered.

Short-Term Outcomes of Surgery for Graves' Disease in Germany

BACKGROUND

Surgical treatment of Graves' disease (GD) has a potentially increased incidence of postoperative hypoparathyroidism, recurrent laryngeal nerve palsy (RLNP) and bleeding. The aim of this study was to evaluate the current extent of surgery for the treatment of GD and its safety as a short-term outcome.

METHODS

Patients who underwent thyroid resection for GD were identified from the prospective StuDoQ/Thyroid registry. Patient data were retrospectively analyzed regarding demographics, surgical procedures and perioperative outcomes. Statistics were performed with Student's t-test or Fisher's exact test and multivariate Cox regression analysis. The level of statistical significance was set at p < 0.05.

RESULTS

A total of 1808 patients with GD with a median age of 44 (range 14-85) years were enrolled in a 25-month period by 78 departments, of which 35.7% (n = 645) had an endocrine orbitopathy and 0.1% (n = 6) had thyrotoxic crisis. Conventional open surgery was used in 98.6% of cases and minimally invasive or remote-access approaches were used in 1.4%. Total thyroidectomy was performed in 93.4% of cases (n = 1688). Intraoperative neuromonitoring (IONM) was used in 98.9% (n = 1789) of procedures. In 98.3% (n = 1777) at least one parathyroid gland was visualized and in 20.7% (n = 375) parathyroids were autografted. The rates of unilateral and bilateral transient RLNP were 3.9% (n = 134/3429 nerves at risk) and 0.1% (n = 4/3429 NAR). The rates of transient RLNP tended to be higher when intermittent IONM was used compared to continuous IONM (4.1% vs. 3.4%, p < 0.059). The rate of transient postoperative hypoparathyroidism was overall 29% (n = 525/1808). Multivariate analysis revealed fewer than 300 thyroid resections and fewer than 15 thyroid resections for GD per year, male sex, BMI > 30, autotransplantation of parathyroid glands and previous bilateral thyroid surgery as independent risk factors for postoperative temporary hypoparathyroidism. Reoperations for bleeding (1.3%) were rare.

CONCLUSION

Total thyroidectomy with IONM is safe and currently the most common surgical therapy for GD in Germany. Postoperative hypoparathyroidism is the major complication which should be focused on.

Hyperthyroidism

Hyperthyroidism is a condition where the thyroid gland produces and secretes inappropriately high amounts of thyroid hormone which can lead to thyrotoxicosis. The prevalence of hyperthyroidism in the United States is approximately 1.2%. There are many different causes of hyperthyroidism, and the most common causes include Graves' disease (GD), toxic multinodular goiter and toxic adenoma. The diagnosis can be made based on clinical findings and confirmed with biochemical tests and imaging techniques including ultrasound and radioactive iodine uptake scans. This condition impacts many different systems of the body including the integument, musculoskeletal, immune, ophthalmic, reproductive, gastrointestinal and cardiovascular systems. It is important to recognize common cardiovascular manifestations such as hypertension and tachycardia and to treat these patients with beta blockers. Early treatment of cardiovascular manifestations along with treatment of the hyperthyroidism can prevent significant cardiovascular events. Management options for hyperthyroidism include anti-thyroid medications, radioactive iodine, and surgery. Anti-thyroid medications are often used temporarily to treat thyrotoxicosis in preparation for more definitive treatment with radioactive iodine or surgery, but in select cases, patients can remain on antithyroid medications long-term. Radioactive iodine is a successful treatment for hyperthyroidism but should not be used in GD with ophthalmic manifestations. Recent studies have shown an increased concern for the development of secondary cancers as a result of radioactive iodine treatment. In the small percentage of patients who are not successfully treated with radioactive iodine, they can undergo re-treatment or surgery. Surgery includes a total thyroidectomy for GD and toxic multinodular goiters and a thyroid lobectomy for toxic adenomas. Surgery should be considered for those who have a concurrent cancer, in pregnancy, for compressive symptoms and in GD with ophthalmic manifestations. Surgery is cost effective with a high-volume surgeon. Preoperatively, patients should be on anti-thyroid medications to establish a euthyroid state and on beta blockers for any cardiovascular manifestations. Thyroid storm is a rare but life-threatening condition that can occur with thyrotoxicosis that must be treated with a multidisciplinary approach and ultimately, definitive treatment of the hyperthyroidism.