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Risk Factors for Postoperative Hypothyroidism

Dorival De Carlucci Jr, MD; Marcos Roberto Tavares, MD; Marcos Takeo Obara, MD; Leandro Augusto Liporoni Martins, MD; Flávio Carneiro Hojaij, MD; Claudio Roberto Cernea, MD

Arch Otolaryngol Head Neck Surg. 2008;134(10):1076-1079.

Objective  To evaluate the incidence of postoperative hypothyroidism among patients who underwent unilateral total lobectomy and identify related factors.

Design  Retrospective medical record analysis.

Setting  Oncological center and private clinic.

Patients  From March 1996 to July 2005, 228 euthyroid patients underwent unilateral total lobectomy for benign diseases; 168 had all the information required for inclusion in this study.

Main Outcome Measures  Serum levels of thyrotropin and antithyroidal antibodies were assessed, as well as ultrasonographic evaluation of the remaining thyroid lobe and review of all histological specimens, with emphasis on lymphocytic infiltration. Hypothyroidism was defined as thyrotropin level greater than 5.5 mU/L.

Results  Most patients were female (88%), with a median (range) age of 45 (16-72) years. Hypothyroidism occurred in 61 cases (32.8%), during a median follow-up period of 29 months (range, 6-108 months). Statistically related factors included higher preoperative thyrotropin levels (2.1 mU/L among hypothyroid patients vs 1.2 mU/L in euthyroid patients; P < .001), smaller thyroid remnant volume (3.9 mL vs 6.0 mL, respectively; P = .003); right vs left lobectomy (P = .006), and higher thyroperoxidase antibody serum levels (P = .009).

Conclusions  Postoperative hypothyroidism appeared in 32.8% of the cases in this series, especially among patients with elevated preoperative thyrotropin and postoperative thyroperoxidase antibody levels, after right lobectomy and when a smaller thyroid remnant was left. After confirmation with larger prospective series, these results may support the indication for early postoperative hormone supplementation in these instances.

Author Affiliations: Department of Head and Neck Surgery, University of São Paulo Medical School, São Paulo, Brazil.