title: Parathyroid hormone levels 4 hours after surgery do not accurately predict post-thyroidectomy hypocalcemia.
abstract: BACKGROUND
  We evaluated the reliability of intact parathyroid hormone (iPTH) levels 4 hours after thyroidectomy (4h-iPTH) as a predictor of hypocalcemia in a large series of patients.
  
  
  METHODS
  A prospective experimental design involving 523 consecutive patients between September 1, 2004, and June 30, 2005, was employed. The specificity, sensitivity, and overall accuracy of 4h-iPTH in predicting post-thyroidectomy hypocalcemia and symptoms were determined.
  
  
  RESULTS
  A total of 199 patients developed hypocalcemia (serum calcium concentrations <8.0 mg/dl). Five patients still were receiving vitamin D/oral calcium at 6 months after the operation. Seventy-three patients experienced mild symptoms. The 4h-iPTH levels were reduced in hypocalcemic patients (28.8 +/- 15.3 vs 11.2 +/- 11.6 pg/ml) (P < .001). The 4h-iPTH levels were within the normal range (10 to 65 pg/ml) in 360 patients (290 normocalcemic) and subnormal in 163 patients (129 hypocalcemic, of whom 62 were symptomatic). The accuracy of 4h-iPTH levels <10 pg/ml in predicting post-thyroidectomy hypocalcemia and symptoms was 80.1% and 78.6%, respectively. False-negative results were observed in 70 hypocalcemic patients (13.4%), 11 of whom were symptomatic (2.1%).
  
  
  CONCLUSIONS
  Subnormal 4h-iPTH levels alone did not accurately predict clinically relevant postoperative hypocalcemia. The optimal cut-off level and its integration with preoperative and postoperative serum calcium concentrations should be reconsidered.
authors.affiliation: Division of Endocrine Surgery, Università Cattolica del Sacro Cuore, Rome, Italy.
authors.forename: Celestino Pio
authors.initials: CP
authors.lastname: Lombardi
authors.forename: Marco
authors.initials: M
authors.lastname: Raffaelli
authors.forename: Pietro
authors.initials: P
authors.lastname: Princi
authors.forename: Chiara
authors.initials: C
authors.lastname: Dobrinja
authors.forename: Cinzia
authors.initials: C
authors.lastname: Carrozza
authors.forename: Enrico
authors.initials: E
authors.lastname: Di Stasio
authors.forename: Annamaria
authors.initials: A
authors.lastname: D'Amore
authors.forename: Cecilia
authors.initials: C
authors.lastname: Zuppi
authors.forename: Rocco
authors.initials: R
authors.lastname: Bellantone
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002118:Calcium / Q000097:blood; D005260:Female; D006801:Humans; D006996:Hypocalcemia / Q000097:blood* / Q000175:diagnosis / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D011184:Postoperative Period; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013965:Thyroidectomy / Q000009:adverse effects*; D013997:Time Factors
chemical_list: D010281:Parathyroid Hormone; D002118:Calcium