
==== Front
Int J Surg
Int J Surg
JS9
International Journal of Surgery (London, England)
1743-9191
1743-9159
Lippincott Williams & Wilkins Hagerstown, MD

38759688
IJS-D-24-01803
10.1097/JS9.0000000000001632
00073
3
Correspondence
Letter to the Editor: a commentary on ‘Predictive factors for persistent hypercalcemia following parathyroidectomy in patients with persistent hyperparathyroidism after kidney transplantation: a retrospective cohort study’
Huang Yiqi MM hyq15925803800@163.com

Shen Weigang MM weigangsheng@126.com

Huang Ailian BD *15157517283@163.com

Department of Nephrology, Shaoxing Second Hospital, Shaoxing, Zhejiang, People’s Republic of China
* Corresponding author. Address: Department of Nephrology, Shaoxing Second Hospital, Shaoxing 312000, Zhejiang, People’s Republic of China. Tel.: +86 151 575 172 83. E-mail: 15157517283@163.com (A. Huang).
9 2024
17 5 2024
110 9 58835884
1 5 2024
6 5 2024
Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. http://creativecommons.org/licenses/by-nc-nd/4.0/

OPEN-ACCESSTRUE
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pmc Dear Editor,

Persistent hyperparathyroidism after kidney transplantation (KT), known as tertiary hyperparathyroidism (THPT), stems from worsening parathyroid gland issues in chronic kidney disease, which increases the risk of bone and heart problems, as well as graft complications. Presently, parathyroidectomy serves as a viable solution for treating THPT that is refractory to pharmacological interventions. However, a subset of patients may continue to exhibit persistent hypercalcemia postoperatively, with the underlying etiology remaining unclear. The retrospective cohort study conducted by Kim et al. examined predictive factors for persistent hypercalcemia following parathyroidectomy in patients with persistent hyperparathyroidism after KT. The findings indicated that the drop rate of intact parathyroid hormone (PTH) less than 88% on postoperative day (POD) 1 and the removal of less than or equal to 2 parathyroid glands were independently correlated with the persistent hypercalcemia post-surgery1.

Nevertheless, it is important to acknowledge the limitations of this study. Most notably, partial THPT and hypercalcemia following KT have the potential to resolve spontaneously within a year, sparking ongoing debate regarding the appropriate indications and timing for parathyroidectomy2. The duration of persistent hypercalcemia, which is considered a prerequisite for thyroidectomy in patients with THPT, remains undefined. It varies from more than 3 months to 12 months, with the most widely accepted and stringent definition requiring at least one year after KT. The criteria established by Kim et al. for persistent hypercalcemia, defined as a serum calcium level of 10.3 mg/dl or higher at the 6-month post-transplant stage1, may lead to an overestimation of the prevalence of persistent hypercalcemia among patients, thus possibly introducing selection bias.

Secondly, certain academics contend that the degree of enhancement in preoperative abnormal indicators is a crucial determinant of surgical success, as demonstrated by a minimum 50% decrease in postoperative PTH levels3. However, Kim et al. did not mention the standard for successful parathyroidectomy surgery, only reporting that the proportion of intact PTH decline on POD 1 in the normocalcemia group was significantly higher than that in the persistent hypercalcemia group (74.4% vs. 18.2%) and that the drop rate of intact PTH less than 88% on POD 1 was an independent risk factor for persistent hypercalcemia1. These findings suggest a strong association between intact PTH decline on POD 1 and persistent hypercalcemia. Nevertheless, the presence of patients exhibiting surgical failure within the persistent hypercalcemia group, characterized by a lack of reduction and subsequent re-elevation of blood calcium levels post-surgery, may introduce substantial inaccuracies in the findings. It is recommended to either exclude such patients from the study or perform subgroup analysis within the hypercalcemia group to mitigate clinical heterogeneity.

Finally, the author analyzed the surgical extent of THPT following KT, finding that the percentage of patients who underwent subtotal thyroparathyroidectomy (54.5%) and the mean number of parathyroid glands removed (3.0±0.7) were notably greater in the normocalcemia group compared to the persistent hypercalcemia group (17.9%, 2.6±0.7). This indicates that employing a broader surgical technique and excising a higher quantity of parathyroid glands results in a more significant decrease in postoperative serum calcium concentrations. The research team of Ohe identified a notable correlation between the extent of parathyroidectomy and the decrease in serum calcium levels at 3 and 6 months following surgery4. Nevertheless, this correlation was not apparent at the 12-month interval. Consequently, we propose an extension of the blood calcium monitoring period to 12 months to delve deeper into this relationship.

In conclusion, this retrospective cohort study provides valuable insights into predictive factors and rational surgical approaches for postoperative persistent hypercalcemia, thereby prompting further discussion within the medical community. By addressing these clinical issues, improvements in the prognosis of patients with persistent hyperparathyroidism following thyroidectomy for KT can be achieved.

Ethical approval

Not applicable

Consent

Not applicable.

Sources of funding

Not applicable.

Author contribution

Y.H., W.S., and A.H.: conceptualization, methodology, validation, formal analysis, investigation, resources, data curation, writing–original draft, writing–review and editing, supervision, project administration.

Conflicts of interest disclosure

The authors declare that there are no conflicts of interest regarding the publication of this paper.

Research registration unique identifying number (UIN)

Not applicable.

Guarantor

Yiqi Huang, Weigang Shen, and Ailian Huang.

Data availability statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study.

Provenance and peer review

Not applicable.

Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.

Published online 17 May 2024
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References

1 Kim BC Kim H Baek CH . Predictive factors for persistent hypercalcemia following parathyroidectomy in patients with persistent hyperparathyroidism after kidney transplantation: a retrospective cohort study. Int J Surg 2024;110 :902–908.37983758
2 Evenepoel P Claes K Kuypers D . Natural history of parathyroid function and calcium metabolism after kidney transplantation: a single-centre study. Nephrol Dial Transplant 2004;19 :1281–1287.14993493
3 Benmiloud F Godiris-Petit G Gras R . Association of autofluorescence-based detection of the parathyroid glands during total thyroidectomy with postoperative hypocalcemia risk: results of the PARAFLUO multicenter randomized clinical trial. JAMA Surg 2020;155 :106–112.31693081
4 Ohe MN Santos RO Kunii IS . Intraoperative PTH cutoff definition to predict successful parathyroidectomy in secondary and tertiary hyperparathyroidism. Braz J Otorhinolaryngol 2013;79 :494–499.23929152
