Post-operative partial hypoparathyroidism: an under-recognized disorder

What are the real rates of temporary hypoparathyroidism following thyroidectomy? It is a matter of definition: a systematic review

INTRODUCTION

Post-operative hypoparathyroidism is the most encountered complication of thyroid surgery and is classified as temporary or permanent. However, its incidence varies greatly in the literature ranging from 0.5% to 65%. This can be mainly attributed to the different definition of hypoparathyroidism used in each study and especially to the different time cutoff applied to distinguish temporary from permanent hypoparathyroidism.

METHODS

We conducted a systematic literature search in PubMed, Scopus, Cochrane and GoogleScholar databases, as well as grey literature. Ultimately, 45 articles with 23,164 patients in total were included in this review. These articles used either the cutoff of six or twelve post-operative months to distinguish temporary from permanent hypoparathyroidism.

RESULTS

The overall incidence of permanent hypoparathyroidism diagnosed at 6 months post-operatively was 4.11% and 4.08% at 12 months post-operatively. There was no statistically significant difference between the two groups (p = 0.92).

CONCLUSIONS

We suggest that adhering to the current guidelines that recommend diagnosing temporary hypoparathyroidism when recovery is made within 6 months after surgery is important when conducting future research in order to narrow the gap that exists currently in the literature, as well as when deciding to put patients on long-term calcium supplements.

Measurement of serum intact parathyroid hormone concentration 1 day after total thyroidectomy to assess risk of permanent hypoparathyroidism

OBJECTIVE

This study was performed to assess the clinical value of measuring the intact parathyroid hormone (iPTH) concentration 1 day after total thyroidectomy to estimate the occurrence of permanent hypoparathyroidism (pHPP).

METHODS

Data of 546 patients who underwent total thyroidectomy from February 2008 to December 2018 were retrospectively analyzed. Calcium and iPTH concentrations were collected preoperatively and at 1 day and 6 months postoperatively. Logistic regression was used to analyze the correlation between clinical indexes and postoperative pHPP.

RESULTS

Of the 546 patients, 22 (4.03%) developed pHPP. Multivariate analysis showed that the iPTH and serum calcium concentrations measured 1 day after surgery were independent predictors of the risk of pHPP. An iPTH concentration of 5.51 pg/mL measured 1 day postoperatively was used as the cut-off value, and the area under the curve was 0.956. The risk of pHPP was identified with a sensitivity of 100%, specificity of 85.1%, positive predictive value of 22%, and negative predictive value of 100%.

CONCLUSIONS

The iPTH concentration measured 1 day after total thyroidectomy is closely related to the occurrence of pHPP postoperatively and is an independent predictive risk factor. The postoperative iPTH concentration can be helpful in identifying patients at risk for developing pHPP.

Parathyroid autotransplantation in thyroid surgery

BACKGROUND

Careful parathyroid gland dissection and in situ preservation was the time-honored approach to prevent parathyroid failure after total thyroidectomy. The relative success of parathyroid autotransplantation of hyperplastic parathyroid tissue in patients with renal or hereditary hyperparathyroidism did popularize the use of normal parathyroid tissue autografts during thyroidectomy to prevent permanent hypoparathyroidism. Proof of autograft function in this setting, however, is controversial.

PURPOSE

This narrative review aims at reviewing critically the current status of parathyroid autotransplantation during total thyroidectomy. It is also meant to analyze from the historical, methodological, and clinical points of view the claimed benefit of normal parathyroid gland autotransplantation. A focus is placed on the prevention of permanent hypoparathyroidism by parathyroid autotransplantation.

CONCLUSIONS

Liberal parathyroid autotransplantation was proposed in the mid 1970s but evidence of function is scarce. Proofs are accumulating that parathyroid autografts not only increase the rate of postoperative hypocalcemia, but may be also contribute to permanent hypoparathyroidism.

The PGRIS and parathyroid splinting concepts for the analysis and prognosis of protracted hypoparathyroidism

Most patients with hypocalcemia after total thyroidectomy will recover the parathyroid function in a few weeks, but some 20-30% of them will still be in the need for replacement therapy one month after surgery and about 5-10% of those will develop permanent hypoparathyroidism. Although postoperative hypocalcemia has been related to several demographic and metabolic causes, parathyroid hormone (PTH) decline, resulting from autotransplantation, inadvertent excision or devascularization of the parathyroid glands, is the common final pathway. The number of parathyroid glands remaining in situ (PGRIS) is a key variable to understand the pathogenesis of protracted hypoparathyroidism and the chances for restoration of the parathyroid function. Normal-high serum calcium concentration, probably achieved by a more intensive medical treatment at the time of hospital discharge, has been identified as an independent variable favoring recovery of the parathyroid function. This we refer to as parathyroid splinting, a hypothesis holding that putting the injured parathyroid parenchyma at rest after thyroidectomy may improve long-term outcome of protracted hypoparathyroidism.

Failure of fragmented parathyroid gland autotransplantation to prevent permanent hypoparathyroidism after total thyroidectomy

PURPOSE

Parathyroid autotransplantation during total thyroidectomy leads to higher rates of postoperative hypocalcaemia. It has been argued, however, that it prevents permanent hypoparathyroidism. The impact of autografted normal parathyroid gland fragments on long-term parathyroid status has not been assessed properly. To clarify this, the short- and long-term parathyroid function was assessed in patients with three glands remaining in situ after total thyroidectomy, in whom the fourth gland was either autotransplanted (Tx) or accidentally resected (AR).

METHODS

Consecutive patients (n = 669) undergoing first-time total thyroidectomy were prospectively studied recording the number of parathyroid glands remaining in situ: PGRIS =4-(glands autografted + glands in the specimen). The study was focused on the subgroup of 186 patients with three parathyroid glands remaining in situ as a result of either accidental resection (AR, n = 76) or autotransplantation into the sternocleidomastoid muscle (Tx, n = 110). Prevalence of postoperative hypocalcaemia, protracted, and permanent hypoparathyroidism were compared between the two groups. Demographic, disease-related, laboratory, and surgical variables were recorded. All patients were followed for at least 1 year.

RESULTS

Both groups were comparable in terms of disease and extent of surgery. Mean postoperative serum calcium was the same (AR: 1.97 ± 0.2 vs Tx: 1.97 ± 0.22 mmol/L). Rates of protracted (AR: 24% vs Tx: 25.5%) and permanent hypoparathyroidism (AR: 5.3% vs Tx: 7.3%) were similar in both groups.

CONCLUSIONS

The prevalence of parathyroid failure syndromes after total thyroidectomy was similar whether a parathyroid gland was inadvertently excised or autotransplanted. Autotransplantation did not influence the permanent hypoparathyroidism rate.

Bilateral benign multinodular goiter: What is the adequate surgical therapy? A review of literature

BACKGROUND

Benign multinodular goiter (BMNG) is the most common endocrine disease requiring surgery. During the last few years a more aggressive approach has become the trend for bilateral BMNG treatment.

METHOD

Randomized clinical trials of any size that compared bilateral subtotal resection, Dunhill procedure and total thyroidectomy for benign multinodular goiter, published between January 2000 and the end of March 2015, were reviewed.

DISCUSSION

Total thyroidectomy can be considered the most reliable approach in preventing recurrence. The Dunhill procedure is related to a higher rate of recurrence, but rarely recurrences after Dunhill procedure lead to reoperation. Total thyroidectomy avoid completion thyroidectomy for incidental carcinoma and its related risks. Recurrent laryngeal nerve (RLN) palsy becomes less common as surgical experience increases. Transient and permanent hypoparathyroidism is strictly related to the extent of neck dissection. In the risk-cost analysis we must consider the type of patient candidated to surgery and the impact of the surgical protocol we apply. When thyroid surgery is taken in consideration, specific complication rates of different procedures in each hospital must be analyzed accordingly to patient-specific risk factors and local expertise.

CONCLUSION

The Dunhill procedure seems to be a good compromise between radicality and prevention of complications, avoiding reoperation for recurrence or completion thyroidectomy for incidental thyroid carcinoma. More follow-up studies and prospective studies are necessary to better evaluate, definitively, whether to prefer total thyroidectomy or Dunhill procedure in case of benign goiter surgery.

Intact parathyroid hormone measurement at 24 hours after thyroid surgery as predictor of parathyroid function at long term

BACKGROUND

There is no consensus about the usefulness of postoperative intact parathyroid hormone (iPTH) determination to predict permanent hypoparathyroidism (pHPP). We evaluated the value of calcium (Ca2+) and iPTH concentration at 24 hours after total thyroidectomy (TT) for predicting pHPP.

METHODS

Ca2+ and iPTH levels from 70 consecutive patients who underwent TT were measured at 24 hours and 6 months after TT.

RESULTS

Five patients (7.1%) developed pHPP. An iPTH concentration ≤5.8 pg/mL at 24 hours after TT identified patients at risk for pHPP (sensitivity, 100%; specificity, 81.5%), but it was not accurate enough to predict its development (positive predictive value, 30%). Conversely, an iPTH level >5.8 pg/mL predicted normal parathyroid function at 6 months (negative predictive value, 100%). Compared with iPTH, a postoperative Ca2+ level ≤1.95 mmol/L was 60% sensitive and 78.5% specific to predict pHPP.

CONCLUSIONS

An iPTH concentration >5.8 pg/mL on the first postoperative day rules out pHPP with much better diagnostic accuracy than Ca2+. Postoperative iPTH could be helpful in identifying patients at risk for developing pHPP.

Complications after total thyroidectomy

The two most common early complications of thyroid surgery are hypocalcemia (20-30%) and recurrent laryngeal nerve injury (5-11%). Bilateral recurrent nerve paralysis resulting in adduction of the vocal cords is a rare life-threatening complication (occurring in less than 0.1% of cases that requires emergency management. Prevention of complications depends on careful operative technique and is enhanced for some teams by the use of specific techniques such as intraoperative neuromonitoring. Postsurgical hypocalcemia is managed by the administration of calcium plus vitamin D for at least 10 days. Recurrent laryngeal nerve paralysis recovers in most cases, and no invasive therapy should be performed for at least six months, except for emergency presentations; laryngeal surgery techniques may offer significant improvement if phonation or respiratory sequelae persist beyond six months, but the results are inconsistent. There should be a systematic strategy for detection of complications after thyroidectomy involving a multidisciplinary approach.