H. M. Yong1, T. W. Yen1, K. Doffek1, D. B. Evans1, T. S. Wang1 1Medical College Of Wisconsin,Department Of Surgery / Division Of Surgical Oncology,Milwaukee, WI, USA
Introduction: Following total thyroidectomy, levothyroxine (LT4) is often prescribed at discharge by the surgical team, with follow-up thyroid function tests (TFTs) and dose adjustments primarily managed by the endocrinologist or primary care physician (PCP). The aim of this study was to investigate the accuracy of the surgical team in determining the initial LT4 dose.
Methods: A retrospective chart review of a prospectively collected, thyroid database was performed of 420 patients with benign thyroid disease who underwent a completion or total thyroidectomy between 1/2009-10/2014 and were prescribed an initial LT4 dose by the surgeon. Data collected included age, gender, body mass index (BMI: kg/m2), pre- and postoperative final pathology, initial surgeon-prescribed LT4 dose, TFTs, subsequent modifications to LT4 dose by the primary care physician/endocrinologist, and the time to achieve biochemical (TSH 0.45 – 4.5 uIU/mL) euthyroidism. All patients had follow-up with an endocrinologist or PCP within 8 weeks of surgery; data on LT4 doses were collected for six months postoperatively.
Results: The final cohort consisted of 289 patients. Median age was 53 years (range, 18-86) and 248 (86%) were female. Median BMI was 31.1 (range, 16.1-63.7). The median LT4 dose initially prescribed was 137 mcg (1.65mcg/kg; range –75-200); 119 (41%) patients achieved normal serum TSH values at initial follow-up and required no dose adjustments. Of the remaining 170 patients, 52 (31%) had elevated TSH levels at initial follow-up, requiring a median adjustment of 25 mcg (range, 11-50). Of the 118 patients with suppressed TSH levels at initial follow-up, the median adjustment was 21.5 mcg (range, 3-60). At 6 months, 59 (34%) of the 170 patients who required an initial dose adjustment had follow-up data; 57 (97%) were euthyroid, achieved at a median of 4.6 months (range, 2–6) and a median of 2 provider visits (range, 2-5).
For the overall cohort, there was no difference in the proportion of patients who required dose adjustment by BMI or race. However, there was a significant difference in the proportion of patients requiring dose adjustment by age; older patients were more likely to be on too high a dose of LT4 at initial follow-up (p=0.0117; Table).
Conclusion: The initial dose of LT4 prescribed by the surgical team after total thyroidectomy was accurate in less than 50% of patients, with more patients being prescribed a higher dose of LT4 than ultimately required, particularly in the elderly. This underscores the importance of follow-up with thyroid function testing within the initial postoperative period and suggests that preoperative discussion with their referring provider for initial LT4 doses may be appropriate.
