Yonsei Med J.  2013 May;54(3):637-642. 10.3349/ymj.2013.54.3.637.

Effectiveness of an i-PTH Measurement in Predicting Post Thyroidectomy Hypocalcemia: Prospective Controlled Study

• Kim JP
• Park JJ
• Son HY
• Kim RB
• Kim HY
• Woo SH

• KMID: 1727876
• DOI: http://doi.org/10.3349/ymj.2013.54.3.637

Abstract

PURPOSE
Hypocalcemia is the most common complication after total thyroidectomy. The purpose of this study was to determine whether measurement of intact parathyroid hormone (i-PTH) level in thyroidectomy patients could predict hypocalcemia.
MATERIALS AND METHODS
We performed a prospective study of patients undergoing total thyroidectomy. Serum concentration of i-PTH, total calcium (Ca), ionized calcium (Ca2+), phosphate (P), magnesium (Mg), and albumin were measured preoperatively and at 0 hour, 6 hours, 12 hours, 24 hours, 48 hours, and 72 hours postoperatively.
RESULTS
108 patients were recruited to the study. A total of 50 patients (46%) experienced hypocalcemia. The serum i-PTH concentration was linearly related to the time of measurement, while concentrations of P, Mg, albumin, Ca, and Ca2+ were not. We compared odds ratios, and found that the concentration of i-PTH at 6 hours post operation was the most closely related to the occurrence of hypocalcemic symptom. On ROC analysis using i-PTH level at 6 hours, an i-PTH level of 10.6 mg/dL was found to maximize both sensitivity and specificity at the same time point.
CONCLUSION
We found that i-PTH was a predictor of hypocalcemia, and that the earliest predictor of hypocalcemic symptoms was an i-PTH concentration lower than 10.6 mg/dL obtained 6 hours after total thyroidectomy.

Keyword

Thyroidectomy; hypocalcemia; parathyroid hormone; surgery

MeSH Terms

Calcium/blood
Humans
Hypocalcemia/*diagnosis
Magnesium/blood
Odds Ratio
Parathyroid Hormone/*blood
Phosphates/blood
Postoperative Complications/blood/*diagnosis
Prospective Studies
Serum Albumin
Thyroidectomy/*adverse effects
Parathyroid Hormone
Phosphates
Serum Albumin
Magnesium
Calcium

Figure

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  Fig. 1 Enrollment in the current study.

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  Fig. 2 Comparison by Mann-Whitney test of preoperative and postoperative serum concentrations between patients with and without hypocalcemic symptoms. Ca, calcium; i-Ca, ionized calcium; Mg, magnesium; P, phosphate; alb, albumin; i-PTH, intact parathyroid hormone; Pre, preoperative; Post, postoperative; No, patients with no hypocalcemic symptoms; Hypo, Patients with hypocalcemic symptoms; OP, operation; h, hour.

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  Fig. 3 Receiver operating characteristic (ROC) analysis for the prediction of hypocalcemic symptoms, based on 6-hour post-thyroidectomy i-PTH values. For 6-hour i-PTH ≤10.6 mg/dL, specificity is 88% and sensitivity is 89%. Area under an ROC curve=0.931. i-PTH, intact parathyroid hormone.

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