Changes in thyroid function and immunological parameters long after subtotal thyroidectomy for Graves' disease.

Objective: To find out whether subtotal thyroidectomy results in long term stable functional and immunological remission in patients with Graves' disease.

Design: Retrospective study.

Setting: Teaching hospital, Japan.

Subjects: 176 patients who underwent subtotal thyroidectomy for Graves' disease, 1970-79.

Intervention: Follow up surveys in 1984 and 1992.

Main Outcome Measures: Changes in thyroid function, antibody titres, and lymphocyte subsets.

Results: 29/79 patients (39%) who were euthyroid in 1984 had evidence of thyroid dysfunction in 1992. Of the 8 patients with latent hypothyroidism in 1984, 3 (38%) had become euthyroid by 1992, and none required treatment. Of the 29 patients who were hypothyroid in 1984, 5 had latent hypothyroidism and 1 was euthyroid in 1992, and of the 18 patients with recurrent hyperthyroidism in 1984, 1 had become euthyroid by 1992. The number of positive titres to TSH-binding inhibitory immunoglobulin was significantly higher in the recurrence group (31/36, 86%) compared with the hypothyroid (7/26, 27%), latent hypothyroidism (8/37, 22%), and euthyroid (22/77, 29%) groups (p < 0.01). There were also significant differences in the mean (SD) number of Leu HLA DR subsets between the control (17 (3), n = 18) and recurrence (21 (6), n = 38), hypothyroid (22 (6), n = 35), latent hypothyroidism (22 (6), n = 22), and euthyroid (22 (9), n = 64) groups (p < 0.002). There were no differences in the number of T cell subsets among the groups.

Conclusion: Treatment of Graves' disease by subtotal thyroidectomy does not necessarily result in stable late functional or immunological remission. Long term follow up of such patients may be necessary.