Parathyroid Hormone as an Early Predictor of Post-thyroidectomy Hypocalcemia

Kim, Joon Ho; Chung, Kyu Whan; Kim, Min Beom; Jeong, Han Sin; Baek, Chung Hwan; Son, Young Ik

Abstract

BACKGROUND AND OBJECTIVES: Parathyroid dysfunction following a total or completion thyroidectomy is not uncommon and it may be associated with significant patient morbidity. If there is a simple test with proven high predictability for identifying which patients will develop hypocalcemia, it would be very useful to determine the necessities of careful monitoring and calcium replacement. The purpose of this study is to determine which test would be the most valuable predictor of post-thyroidectomy hypocalcemia.
SUBJECTS AND METHOD
Prospective series of 63 consecutive patients undergoing total or completion thyroidectomy were enrolled for this study. Calcium and ionized calcium were measured before and immediately after surgery, and daily during hospitalization. Parathyroid hormone (PTH) was measured immediately after surgery and early in the morning of the next day. Slopes of serum calcium, ionized calcium and PTH level change were calculated. Sensitivity, specificity and predictive values of each test for the symptomatic and biochemical hypocalcemia were compared.
RESULTS
With the cut-off value of 10 pg/ml of spot PTH, sensitivity, specificity, positive and negative predictive values of hypocalcemia were 97%, 64%, 77% and 95% respectively. By combining the spot PTH and the slope of ionized calcium change, the above values became 94%, 82%, 87% and 92%.
CONCLUSION
Immediate postoperative spot PTH level was the most valuable single test for predicting post-thyroidectomy hypocalcemia. Combination of a spot PTH and the slope of ionized calcium change resulted in improved specificity and positive predictability.