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.