Changes in the thyroid function of Graves' disease patients treated by subtotal thyroidectomy.

The extent of thyroidectomy in Graves' disease is still a matter of controversy. Subtotal thyroidectomy has been used as the standard surgical procedure for Graves' disease in Japan, but high hyperthyroidism relapse rates have been reported. We retrospectively studied serial changes in the thyroid function Graves' disease patients after they had been treated by subtotal thyroidectomy and assessed whether subtotal thyroidectomy should be recommended as the standard surgical procedure for the treatment of Graves' disease. The subjects were 478 Graves' disease patients who underwent subtotal thyroidectomy at our institution between 1994 and 1997 and were followed up on a regular basis, and their thyroid function 2-3 years after surgery (the early period) and 8-10 years after surgery (the late period) was evaluated and compared. The evaluations in the late period showed that 57% of the euthyroid patients in the early period remained euthyroid, 30% had developed a relapse of hyperthyroidism, and 13 % had become hypothyroid. Approximately 80% of the patients who were overtly hyperthyroid or overtly hypothyroid in the early period remained so in the late period. During the entire periods 47 patients had subclinical hyperthyroidism and were followed up without any postoperative medication. Twenty (42.6%) of them developed overt hyperthyroidism, 11 (23.4%) experienced a spontaneous remission, and 16 (34%) continued to be subclinically hyperthyroid. Because thyroid function after subtotal thyroidectomy is unstable and reduces quality of life, subtotal thyroidectomy is concluded not to be suitable as a standard surgical procedure for the treatment of Graves' disease.