Abstract
Objective
Total thyroidectomy represents the gold standard surgical procedure for patients with malignant thyroid disease. Over the past decades, the total thyroidectomy gradually replaced the subtotal thyroidectomy for benign thyroid disorders as well. Postoperative hypocalcemia remains the most frequent complication. The close proximity of parathyroid glands to the thyroid capsule leads often to devascularization or adventitious removal of parathyroid tissue. Clinical symptoms like paresthesia, tingling, muscle cramps or seizures often occur. Combined measurement of intact parathyroid hormone (iPTH) and calcium after the operation are used worldwide to predict postoperative hypoparathyroidism. The purpose of this study was to find out the incidence of decreased iPTH at the end of surgery and its reliability in predicting hypocalcemia.
Methods
We performed a retrospective analysis of 534 patients who underwent total thyroidectomy at our institution between 2000 and 2019. Medical records were reviewed to analyze the patient characteristics, indication of the procedure, laboratory and histological results, postoperative management and complications. The iPTH was measured before and at the end of the surgery, while the calcium was measured at the first postoperative day. The iPTH assay at our hospital has a normal range between 15.0 and 80.0 pg/ml. Meanwhile hypocalcemia was defined as a calcium measurement < 2.2 mmol/l.
Results
The mean age of the patients was 55.34 years. The female to male ratio was 4.6:1. The mean preoperative iPTH of our cohort was 48.35 pg/ml, while the postoperative iPTH was 31.74 pg/ml, indicating a mean reduction of 35.75%. A total of 174 patients (32.6%) had a iPTH < 15.0 pg/ml at the end of the surgery, indicating a reduction of 75.6%. 22 of these 174 patients (12.6%) developed clinical symptoms of hypocalcemia. In contrast only 3 patients (0.08%) with normal iPTH developed symptoms. Whole parathyroid glands were identified in 95/534 (17.8%), whereas from the 174 patients with iPTH < 15.0 pg/ml, 56 (32.2%) had at least one parathyroid gland in the operative specimens.
Conclusion
Measurement of iPTH at the end of total thyroidectomy is a good predictor to detect patient who are at risk for developing symptomatic hypocalcemia and calcium substitution can be started at the same day. A normal iPTH almost excludes symptomatic hypocalcemia.
Does the number of autotransplanted parathyroid glands affect postoperative hypoparathyroidism and serum parathyroid hormone levels?
