title: Does preoperative 25-hydroxyvitamin D status significantly affect the calcium kinetics after total thyroidectomy?
abstract: BACKGROUND
  Although previous studies have suggested that low preoperative 25-hydroxyvitamin D (25-OHD) is a risk factor for hypocalcemia after total thyroidectomy, the impact of preoperative 25-OHD on calcium (Ca)/parathyroid hormone (PTH) kinetics in the immediate postoperative period remains unclear. The study compared the postoperative Ca/PTH kinetics between different preoperative 25-OHD levels.
  
  
  METHODS
  A total of 281 patients who underwent a total thyroidectomy were analyzed. Serum Ca was measured preoperatively within 1 h after surgery (Ca-D0) and on the following morning (Ca-D1). Preoperative 25-OHD was also measured after overnight fasting while postoperative PTH was checked at skin closure on day 0 (PTH-D0) and on the following morning on day 1 (PTH-D1). The Ca/PTH kinetics were compared between three groups (group I: preoperative 25-OHD < 10 ng/mL; group II: 25-OHD = 10-20 ng/mL; group III: 25-OHD > 20 ng/mL).
  
  
  RESULTS
  Group I had significantly lower preoperative Ca (p = 0.016) and Ca-D0 (p = 0.036) but higher PTH-D1 (p = 0.015) than groups II and III. PTH-D0, Ca-D1, and the rate of clinically significant hypocalcemia were similar in the three groups. Group I had a significantly smaller Ca drop (-0.02 vs. 0.01 and 0.02 mmol/L, p = 0.011) and a tendency for a significantly smaller PTH drop (0.4 vs. 0.5 and 1.0 pmol/L, p = 0.073) than groups II and III. PTH-D1 (OR = 1.550) and 25-OHD (OR = 0.958) were independent factors for Ca drop from day 0 to day 1.
  
  
  CONCLUSIONS
  Although group I began with lower serum Ca, those patients tended to have a greater PTH response to Ca drop and so preoperative 25-OHD did not significantly affect the overall Ca kinetics from preoperative to day 1.
authors.affiliation: Division of Endocrine Surgery, Department of Surgery, University of Hong Kong, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong SAR, China. blang@hkucc.hku.hk
authors.forename: Brian Hung-Hin
authors.initials: BH
authors.lastname: Lang
authors.forename: Kai Pun
authors.initials: KP
authors.lastname: Wong
authors.forename: Chung Yeung
authors.initials: CY
authors.lastname: Cheung
authors.forename: Yuen Ki
authors.initials: YK
authors.lastname: Fong
authors.forename: Desmond Kwan-Kit
authors.initials: DK
authors.lastname: Chan
authors.forename: Grace Kin-Yee
authors.initials: GK
authors.lastname: Hung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D002118:Calcium / Q000097:blood*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006996:Hypocalcemia / Q000097:blood / Q000175:diagnosis / Q000209:etiology*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D011183:Postoperative Complications / Q000097:blood / Q000175:diagnosis / Q000209:etiology*; D057234:Preoperative Period; D011446:Prospective Studies; D012307:Risk Factors; D013965:Thyroidectomy; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications* / Q000175:diagnosis
chemical_list: D015415:Biomarkers; D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D; D002118:Calcium