Scientific paper Detecting and defining hypothyroidism after hemithyroidectomy Hannah G. Piper, M.D. a , Samuel P. Bugis, M.D. a , Graeme E. Wilkins, M.D. b , Blair A.M. Walker, M.D. c , Sam Wiseman, M.D. a , Christopher R. Baliski, M.D. a, * a Department of Surgery, Division of General Surgery, St. Paul’s Hospital, University of British Columbia, 1081 Burrard Street, Vancouver, British Columbia V6Z 1Y6, Canada b Division of Endocrinology, St. Paul’s Hospital, University of British Columbia, Vancouver, British Columbia, Canada c Department of Pathology and Laboratory, St. Paul’s Hospital, University of British Columbia, Vancouver, British Columbia, Canada Manuscript received December 23, 2004; revised manuscript January 28, 2005 Presented at the 91st Annual Meeting of the North Pacific Surgical Association, Tacoma, Washington, November 12–13, 2004 Abstract Background: The incidence of hypothyroidism after hemithyroidectomy for benign thyroid disease remains uncertain. This study examines the incidence, natural history, and the factors contributing to hypothyroidism after hemithyroidectomy. Methods: A retrospective review of patients undergoing hemithyroidectomy over 37 months was performed. The incidence of postoper- ative hypothyroidism was based on thyrotropin values and clinical symptoms. The relationship between hypothyroidism and lymphocytic infiltration of the removed gland was investigated using stepwise logistic regression. Results: Twelve of 66 patients (18%) became biochemically hypothyroid postoperatively. Four of the 12 patients (33%) subsequently became euthyroid without intervention. Of the remaining 8 patients, 4 (50%) had significant lymphocytic infiltration in the resected gland compared with 10 (19%) of the 54 euthyroid patients. Lymphocytic infiltration was associated with hypothyroidism but was age dependent. Conclusions: A minority of patients become hypothyroid after hemithyroidectomy. Some patients with biochemical hypothyroidism will become euthyroid without intervention. The impact of lymphocytic infiltrate on hypothyroidism after hemithyroidectomy is age dependent. © 2005 Excerpta Medica Inc. All rights reserved. Keywords: Hypothyroidism; Hemithyroidectomy; Follow-up; Lymphocytic infiltration Traditionally, a significant portion of patients have been placed on thyroid hormone replacement after hemithyroid- ectomy for benign goiter. The most common indications for treating patients with thyroxine have included prevention of goiter recurrence, reduction of the risk of malignant con- version, and treatment of hypothyroidism [1]. There is no clear evidence to support a benefit in the first two instances. Although hormone replacement is indicated for hypothyroid patients, this diagnosis is not always straightforward. There have been several studies evaluating thyroid function after hemithyroidectomy for benign thyroid disease [1–7]. The reported incidence of hypothyroidism ranges from 5% to 35% depending on the follow-up interval and how the investigators define hypothyroidism. These reports have led to our interest in establishing precise criteria for defining postoperative hypothyroidism, thereby identifying patients at greatest risk for requiring chronic thyroid hormone re- placement. Currently, there is no clear schedule for postoperative assessment of residual thyroid function in individuals who have undergone hemithyroidectomy. In most cases, the fol- low-up is left to the discretion of the patient’s surgeon and family physician based on clinical suspicion or the devel- opment of symptomatic disease. Although it is known that chronic autoimmune thyroiditis can lead to a progressive decline in thyroid function, the significance of lymphocytic infiltration within a resected gland is unclear [1,2]. There is currently evidence to suggest that patients with glandular lymphocytic infiltration are at increased risk of developing hypothyroidism [2], but this is not used in the postoperative management of these patients. The aim of this study was to determine the incidence of hypothyroidism in patients after hemithyroidectomy and to * Corresponding author. Tel: +1-604-806-9108; fax: +1-604-806-8666. E-mail address: cbaliski@providencehealth.bc.ca The American Journal of Surgery 189 (2005) 587–591 0002-9610/05/$ – see front matter © 2005 Excerpta Medica Inc. All rights reserved. doi:10.1016/j.amjsurg.2005.01.038