Background and Pathology

 

Parathyroid hormone (PTH), produced by four parathyroid glands in the neck, plays an important role in calcium homeostasis. Primary hyperparathyroidism (PHPT) is a condition that results in excess production of PTH by growth (mostly benign tumour or hyperplasia) of one or more of the parathyroid glands. PHPT may result in increased circulatory calcium levels that negatively impact other organs like the kidneys with increased stone formation and the bones with increased risk of fracture and loss of bone mass.

 

Parathyroidectomy (surgical removal of the affected gland(s)) is the only definitive treatment for PHPT [1]. Post-operative complications include recurrence or persistence of hypercalcemia may be reduced by proper preoperative localizing imaging along with intraoperative monitoring of PTH levels (ioPTH) before and after gland(s) resection [2]. 

 

PTH has a very short half-life (3 – 5 minutes), so its level drops quickly and significantly after the removal of the abnormal gland(s). A reduction in PTH levels by more than 50% after surgical resection of the affected gland(s) (as compared to a baseline pre-ligation level) is indicative of complete and successful resection. It was shown that monitoring of ioPTH reduced operative conversion of minimally invasive parathyroidectomy into more invasive bilateral neck exploration [2] [3].

 

New Test

 

HRLMP, in collaboration with the head and neck surgery team at McMaster, now provides ioPTH testing at St-Joseph’s core laboratory. The test is performed on plasma samples collected during the parathyroidectomy operation and tested on a Roche Cobas e 4111 analyzer. Samples need centrifugation for one minute and 9 minutes on the Roche analyzer.

 

To ensure delivering this time-sensitive “boutique” service, a dedicated MLT is assigned to process the samples and promptly report the results to the surgery team during the entire length of the operation. This service also requires timely planning and communication between the surgery team and the core laboratory ahead of the surgery for staff scheduling and instrument preparation and during the surgery for sample delivery and result reporting. The ioPTH test provides fast access to real-time results and minimizes the need for preparation and revision of frozen tissue sections.

 

Bibliography

 

[1]

M. Lala, "Indian Journal of Surgical Oncology," vol. 13, no. 1, p. 143 –151, 2022.

[2]

Aabid Hassan Naik, "Intraoperative Parathyroid Hormone Monitoring in Guiding Adequate Parathyroidectomy," Indian Journal of Endocrinology and Metabolism, vol. 22, no. 410-6, 2018.

[3]

S. v. S. O. ̈. .. M. a. L. B. A. Bergenfelz, "European multicentre study on outcome of surgery for sporadic primary hyperparathyroidism," BJS, vol. 108, p. 675–683, 2021.

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