Applicability of intraoperative parathyroid hormone assay during thyroidectomy.
OBJECTIVE
To evaluate the applicability of intraoperative parathyroid hormone (quick PTH) assay to monitor parathyroid function and to identify clinically significant hypocalcemia compared with postoperative serum calcium monitoring.


BACKGROUND
Close monitoring of serum calcium levels is a standard of care to identify post-thyroidectomy hypocalcemia due to parathyroid insufficiency.


METHODS
Quick PTH assay was performed before and after thyroidectomy for 100 patients at risk of postoperative hypocalcemia and 20 control patients who underwent unilateral lobectomy. Postoperative serum calcium levels were closely monitored.


RESULTS
Control patients had a normal but 38.9 +/- 5.9% (mean +/- SEM) decline in quick PTH after thyroidectomy. Eleven of 100 at-risk patients (11%) developed postoperative hypocalcemia. Hypocalcemic patients had significantly lower quick PTH values after thyroidectomy compared with that of normocalcemic patients. Serum calcium was significantly lower in hypocalcemic patients the morning after operation but not early after the operation (within 6 hours). A normal or less than 75% decline in quick PTH after thyroidectomy can accurately identify normocalcemic patients during surgery as compared to more than 24 hours by serum calcium monitoring.


CONCLUSIONS
The quick PTH assay can monitor parathyroid function during thyroidectomy and identify patients at risk of clinically significant hypocalcemia much earlier than serum calcium monitoring. It may facilitate early discharge and the use of parathyroid autotransplantation during thyroidectomy.
Lo
Chung Yau
CY
Department of Surgery and Division of Clinical Biochemistry, the University of Hong Kong Medical Centre, Queen Mary Hospital, Hong Kong, China. cylo@hkucc.hku.hk
Luk
John M
JM
Tam
Sidney C
SC
D000328:Adult; D000368:Aged; D002118:Calcium / Q000097:blood; D005260:Female; D006801:Humans; D006996:Hypocalcemia / Q000175:diagnosis / Q000209:etiology; D007118:Immunoassay; D015592:Immunoradiometric Assay; D007432:Intraoperative Period; D008163:Luminescent Measurements; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D013965:Thyroidectomy / Q000009:adverse effects
D010281:Parathyroid Hormone; D002118:Calcium