The selective beta 1-blocking agent metoprolol compared with antithyroid drug and thyroxine as preoperative treatment of patients with hyperthyroidism. Results from a prospective, randomized study.

Despite the increasing use of beta-blocking agents alone as preoperative treatment of patients with hyperthyroidism, there are no controlled clinical studies in which this regimen has been compared with a more conventional preoperative treatment. Thirty patients with newly diagnosed and untreated hyperthyroidism were randomized to preoperative treatment with methimazole in combination with thyroxine (Group I) or the beta 1-blocking agent metoprolol (Group II). Metoprolol was used since it has been demonstrated that the beneficial effect of beta-blockade in hyperthyroidism is mainly due to beta 1-blockade. The preoperative, intraoperative, and postoperative courses in the two groups were compared, and patients were followed up for 1 year after thyroidectomy. At the time of diagnosis, serum concentration of triiodothyronine (T3) was 6.1 +/- 0.59 nmol/L in Group I and 5.7 +/- 0.66 nmol/L in Group II (reference interval 1.5-3.0 nmol/L). Clinical improvement during preoperative treatment was similar in the two groups of patients, but serum T3 was normalized only in Group I. The median length of preoperative treatment was 12 weeks in Group I and 5 weeks in Group II (p less than 0.01). There were no serious adverse effects of the drugs during preoperative preparation in either treatment group. Operating time, consistency and vascularity of the thyroid gland, and intraoperative blood loss were similar in the two groups. No anesthesiologic or cardiovascular complications occurred during operation in either group. One patient in Group I (7%) and three patients in Group II (20%) had clinical signs of hyperthyroid function during the first postoperative day. These symptoms were abolished by the administration of small doses of metoprolol, and no case of thyroid storm occurred. Postoperative hypocalcemia or recurrent laryngeal nerve paralysis did not occur in either group. During the first postoperative year, hypothyroidism developed in two patients in Group I (13%) and in six patients in Group II (40%). No patient had recurrent hyperthyroidism. The results suggest that metoprolol can be used as sole preoperative treatment of patients with hyperthyroidism without serious intra- or postoperative complications. Although the data indicate that the risk of postoperative hypothyroidism is higher after preoperative treatment with metoprolol than with an antithyroid drug, a longer follow-up period than 1 year is needed to draw conclusions regarding late results.