An evaluation of several prognostic factors in the surgical treatment for thyrotoxicosis.

: A follow-up survey of 447 patients who had undergone a subtotal thyroidectomy was carried out. In this study, 433 patients were observed, and the follow-up period ranged from one year to ten years. The incidence postoperatively of a recurrence and hypothyroidism was 9.6 and 2.3 per cent, respectively. Transient subclinical hypothyroidism was observed in most patients within three to six months after the operation. This state, however, recovered spontaneously to the euthyroid state within one year. Recurrent hyperthyroidism tends to increase with the lapse of years, while permanent hypothyroidism developed during the first or second year after operation. Results of our investigation suggest that the size of the remnant thyroid appears to play the most important role for an expected long term remission, and the optimal weight of the remnant thyroid should be approximately 10 grams. Although the precise mechanism of remission by surgical ablation of the thyroid has not been clarified, surgical treatment is an effective and safe procedure which controls the condition of the patient with thyrotoxicosis.