Detecting and defining hypothyroidism after hemithyroidectomy.

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 postoperative 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.