Thyroid surgery in untreated severe hyperthyroidism: perioperative kinetics of free thyroid hormones in the glandular venous effluent and peripheral blood.

BACKGROUND AND METHODS

It is generally believed that thyroid surgery in Graves' disease requires a euthyroid state to avoid thyrotoxic reactions. We carried out a prospective study on 23 patients who had severe hyperthyroidism with free thyroid hormone concentrations (fT3 or fT4) exceeding the upper normal boundary by 300% or more and who were not pretreated with thyrostatic agents. We determined hormone levels during operation in the thyroid venous effluent before and after surgical trauma and monitored their postoperative elimination kinetics.

RESULTS

The concentration of fT3 and fT4 in the venous effluent of the hyperactive gland did not exceed the peripheral levels. Surgery did not induce any intraoperative or postoperative increase in fT4 or fT3, whereas thyroglobulin concentrations rose sharply. Both fT4 and fT3 followed biphasic elimination kinetics, and a significant decline of circulating free hormone concentrations was measurable within the first postoperative hour.

CONCLUSIONS

Contrary to widely held assumptions, the surgical trauma does not stimulate the release of thyroid hormones. Hence this mechanism cannot account for the postoperative development of thyroid storm. Our observations imply that immediate operation should generally be considered for the emergency treatment of an imminent thyroid storm.