Progressive increase in thyroid dysfunction after subtotal thyroidectomy for Graves' disease

It has generally been believed that if hypothyroidism were to occur following subtotal thyroidectomy for Graves' disease, it would do so in the first year or two with little or no risk of long term hypothyroidism. The aim of this study was to determine long term treatment outcomes following surgery for Graves' disease. The thyroid status of 184 patients who had subtotal thyroidectomy was reviewed either by telephone interview or written questionnaire. All patients who were not taking thyroxine therapy had thyroid function tests performed. All patients had had a standardized surgical procedure performed within a single unit, leaving an intended 4 to 5 gm remnant in all cases. Although 51% of patients were euthyroid six months after surgery, there was a continuing and progressive onset of both hypothyroidism and recurrent thyrotoxicosis with time. At 15 years, only 27.4% of patients remained euthyroid, 3.3% had developed recurrent thyrotoxicosis and the remaining 69.3% had become hypothyroid. No permanent complications, permanent hypoparathyroidism or permanent recurrent laryngeal nerve palsy occurred in any patient in the study. It is concluded that subtotal thyroidectomy is a safe and effective treatment modality for Graves' disease. Long-term follow-up with assessment of thyroid function is required however, because of the continuing occurrence of both hypothyroidism and recurrent thyrotoxicosis for many years following surgery.