Hypothyroidisim following hemithyroidectomy: Incidence, risk factors, and management

Background. The purpose; of this study was to characterize the hypothyroidi sm that occur following hemithyroidectomy. Methods. The records of all euthyroid patients who underwent hemithyroidect omy from 1992 to 2000 were reviewed to determine the frequency of postsurgi cal hypothyroidism and the predisposing factors. All patients were evaluate d for age, gender serum thyrotropin (TSH) levels, weight of resected thyroi d tissue, and associated thyroiditis. Hypothyroid patients were evaluated f or symptoms, timing of diagnosis, and treatment doses of levothyroxine (L-T -4). Results. Hypothyroidism was diagnosed in 25 (35%) of 71 patients, subclinic al in 16 and overt in 9 with a mean postoperative TSH level of 8.51 +/- 6.5 3 mu IU/L. The mean preoperative TSH level was 1.94 +/- 1.00 mu IU/L in hyp othyroid compared with 1.10 +/- 0.74 mu IU/L in euthyroid patients (P < 05) . Lymphocytic thyroiditis was present in 10 (40%) of 25 hypothyroid compare d with 10 (22%) of 46 euthyroid patients (P = not significant). There were no significant differences in age, gender, or weight of resected thyroid ti ssue. The average therapeutic dose of L-T-4 was 1.3 <mu>g/kg (range, 0.5 to 1.9 mug/kg). All but 2 hypothyroid patients were diagnosed within 2 months of operation. Conclusions. Hypothyroidism following hemithyroidectomy occurs in patients with higher preoperative TSH levels, is usually mild and asymptomatic, and can be treated with reduced doses of L-T-4.