Hypothyroidisim following hemithyroidectomy: incidence, risk factors, and management

BACKGROUND: The purpose of this study was to characterize the hypothyroidism that occurs following hemithyroidectomy. METHODS: The records of all euthyroid patients who underwent hemithyroidectomy from 1992 to 2000 were reviewed to determine the frequency of postsurgical hypothyroidism and the predisposing factors. All patients were evaluated for age, gender, serum thyrotropin (TSH) levels, weight of resected thyroid tissue, and associated thyroiditis. Hypothyroid patients were evaluated for symptoms, timing of diagnosis, and treatment doses of levothyroxine (L-T(4)). RESULTS: Hypothyroidism was diagnosed in 25 (35%) of 71 patients, subclinical in 16 and overt in 9 with a mean postoperative TSH level of 8.51 +/- 6.53 microIU/L. The mean preoperative TSH level was 1.94 +/- 1.00 microIU/L in hypothyroid compared with 1.10 +/- 0.74 microIU/L in euthyroid patients (P <.05). Lymphocytic thyroiditis was present in 10 (40%) of 25 hypothyroid compared with 10 (22%) of 46 euthyroid patients (P = not significant). There were no significant differences in age, gender, or weight of resected thyroid tissue. The average therapeutic dose of L-T(4) was 1.3 microg/kg (range, 0.5 to 1.9 microg/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).