Thyroid function after hemithyroidectomy for benign nodules.

In order to assess the need for thyroxine therapy to maintain normal thyroid function in patients who have undergone hemithyroidectomy for benign solitary nodules, pre- and postoperative serum thyroxine (T4) and serum thyrotropin (TSH) concentrations were measured in a prospective study on 103 patients. Thyroid function measurements were normal before the operation. Postoperative thyroid function tests showed a significant reduction of serum T4 at 3 years and a significant elevation of serum TSH between 6 months and 3 years after surgery, but the altered levels remained within the normal range. Thirteen patients had abnormal postoperative thyroid function tests. Eight patients had subnormal T4 levels, which were accompanied by concomitant increases in TSH levels above normal in 3 individuals. Five patients had supranormal TSH values associated with normal T4 levels, but only 1 of them showed clinical recurrence of a goiter. These observations suggest that most patients remain clinically and biochemically euthyroid after hemithyroidectomy. Thus, routine replacement thyroxine therapy is not necessary to prevent biochemical hypothyroidism, but it may be indicated in the few patients in whom a subnormal T4 level develops. The clinical significance of these subtle changes in serum T4 and TSH within the normal range is not clear especially with respect to goiter recurrence.