The value of postoperative parathyroid hormone levels in predicting the need for long-term vitamin D supplementation after total thyroidectomy.
BACKGROUND
Few studies have examined the need for vitamin D supplementation after total thyroidectomy. This study examines the role of postoperative day (POD) 1 serum calcium and parathyroid hormone (PTH) levels in predicting the need for long-term vitamin D supplementation after total thyroidectomy.


METHODS
A retrospective, single institutional study of patients who underwent total thyroidectomy between January 2007 and December 2008 was performed. Data collected included extent of surgery, final pathology, postoperative calcium (mg/dl) and PTH (pg/ml) values, and duration of vitamin D supplementation. Patients were divided into 4 groups based on POD1 PTH values: group 1 (<5.0); group 2 (5.0-10); group 3 (10.1-20); and group 4 (>20).


RESULTS
Of the 104 patients, 26 were in group 1, 12 in group 2, 18 in group 3, and 48 in group 4, with median PTH values of <2.5, 8.2, 14.1, and 30 pg/ml, respectively. All 7 (7%) patients who required vitamin D supplementation >1 month were in group 1. The positive predictive value of POD1 PTH <5.0 in predicting supplementation >1 month was 27% (sensitivity 100%, specificity 80%). Seventy-eight patients had a POD1 PTH level ≥5, and none required vitamin D supplementation >1 month (100% negative predictive value). The positive predictive value of various POD1 calcium thresholds (<7.5, <8.0, and <8.5 mg/dl) was 17, 14, and 15%, respectively.


CONCLUSIONS
Postoperative PTH levels better predict long-term hypocalcemia requiring vitamin D supplementation than serum calcium levels. A PTH level ≥5.0 may identify patients who can be safely discharged without routine vitamin D supplementation.
Division of Surgical Oncology, Department of Surgery, Medical College of Wisconsin, Milwaukee, WI, USA. tswang@mcw.edu
Tracy S
TS
Wang
Ashley K
AK
Cayo
Stuart D
SD
Wilson
Tina W F
TW
Yen
D018263:Adenocarcinoma, Follicular / Q000097:blood* / Q000601:surgery; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002118:Calcium / Q000097:blood; D002291:Carcinoma, Papillary / Q000097:blood* / Q000601:surgery; D015331:Cohort Studies; D019587:Dietary Supplements; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D011379:Prognosis; D012189:Retrospective Studies; D013964:Thyroid Neoplasms / Q000097:blood* / Q000601:surgery; D013965:Thyroidectomy; D013966:Thyroiditis / Q000097:blood* / Q000601:surgery; D014807:Vitamin D / Q000097:blood*; D055815:Young Adult
D014807:Vitamin D; D002118:Calcium