The role and timing of parathyroid hormone determination after total thyroidectomy

Abstract

Postoperative hypocalcemia is a common complication of total thyroidectomy resulting from manipulation, resection, or devascularization of the parathyroid glands. Parathyroid hormone (PTH) levels assessed in the perioperative period have been used to predict development of hypocalcemia. Articles examining the role of PTH measurement in the perioperative period following total or completion thyroidectomy are reviewed. Focus is placed on the timing of PTH measurement and the ability to predict which patients will develop hypocalcemia requiring supplementation. Postoperative PTH determination is highly accurate in predicting the development of hypocalcemia. Studies have examined PTH levels drawn at differing time points, ranging from intraoperatively until postoperative day 1 (POD1) with similar accuracy. This data is used to guide postoperative selective calcium and calcitriol supplementation in patients at highest risk for hypocalcemia. When evaluated within the first 4 hours postoperatively, predictive accuracy is maintained but can allow for earlier discharge for those patients at lower risk. Alternatively, some authors argue for routine supplementation, which can reduce the rate of postoperative hypocalcemia but increases the rate of unnecessary supplementation and potential risks associated with hypercalcemia. PTH determination at four hours after total thyroidectomy is an accurate predictor of hypocalcemia and can guide selective calcium supplementation for those at high risk, as well as facilitate a safe earlier hospital discharge for those at low risk of developing postoperative hypocalcemia.

Keywords: Hypocalcemia; hypoparathyroidism; parathyroid hormone (PTH); thyroidectomy.

Figure 1

Breakdown of the study cohort by POD1 PTH level, supplementation regimen, hypocalcemic symptoms, and need for IV calcium [reprinted with permission from Cayo et al. (1)]. Group A, PTH <5, randomized to supplementation with oral calcium; Group B, PTH <5, randomized to supplementation with oral calcium and calcitriol; Group C, PTH 5–10, randomized to supplementation with oral calcium; Group D, PTH 5–10, randomized to no supplementation; Group E, PTH >10, did not receive routine supplementation.

Figure 2

Algorithm for postoperative inpatient (A) and outpatient (B) management with calcium supplementation following completion/total thyroidectomy. PTH, parathyroid hormone; BID, twice per day.