Prediction of hypothyroidism after hemithyroidectomy: a biochemical and pathological analysis

The possibility of postsurgical hypothyroidism after hemithyroidectomy is no longer a new subject. Although many previous studies have mentioned posthemithyroidectomy hypothyroidism, the incidence and contributing factors for hypothyroidism remain uncertain. We intended to evaluate the incidence and the time of development of hypothyroidism after hemithyroidectomy and to analyze the relationship of posthemithyroidectomy hypothyroidism with preoperative biochemical parameters and postoperative histopathological findings. From February 2001 through December 2004, 287 consecutive cases of hemithyroidectomized patients were retrospectively analyzed; 136 of these patients were included in this study after the exclusion criteria were applied. The relationship between posthemithyroidectomy hypothyroidism and several parameters such as sex, age, preoperative free T4, TSH, microsomal antibody (Ab), thyroglobulin antibody (Ab) levels and lymphocytic infiltration of the resected gland was statistically analyzed. Postoperative hypothyroidism developed in 58 patients (42.6%). In hypothyroid group, 11 patients (19%) showed overt hypothyroidism and 47 patients (81%) showed subclinical hypothyroidism. Preoperative TSH value was significantly higher in the hypothyroid group (2.15 ± 1.30 μU/ml) compared to the euthyroid group (1.29 ± 0.9 μU/ml). Positive ratio of preoperative microsomal Ab and thyroglobulin Ab were significantly higher in hypothyroid group (38.9 and 41.9%) compared to euthyroid group (3.6 and 19.3%) (P <0.05). In addition, patients with a higher grade of lymphocytic infiltration were found to have a higher probability of developing hypothyroidism. About 85% of postoperative hypothyroidism was detected between 1 and 6 months postoperatively. We might predict the possibility of developing the posthemithyroidectomy hypothyroidism especially in case of preoperatively positive microsomal antibody, thyroglobulin antibody and high-grade lymphocytic infiltration of the resected gland. In addition, our findings support the recommendation for regular serum TSH follow-up at least for 12 months after hemithyroidectomy.