Factors affecting thyroid function after thyroidectomy for Graves' disease.

A series of 108 patients with surgically treated Graves' disease were analyzed retrospectively in an attempt to determine factors that could affect postoperative thyroid function. Univariate analysis showed that remnant size, resected thyroid weight, antithyroid microsomal antibody and antithyroglobulin antibody titers were all significantly related to the postoperative outcome. Remnant size outweighed the other factors in prediction of thyroid status following subtotal thyroidectomy. When all the potential prognostic factors were individually adjusted by remnant size, only the degree of lymphocytic infiltration and antithyroid microsomal antibody titer were significantly associated with the postoperative outcome. Within the range of optimal remnant size, the higher the antithyroid microsomal antibody titer and the degree of lymphocytic infiltration, the greater the likelihood of postoperative hypothyroidism and the lower the chance of recurrence. Further stepwise discriminant analysis revealed that remnant size can be planned according to the known preoperative antithyroid microsomal antibody titer to achieve the greatest likelihood of a postoperative euthyroid state. The model suggested that when the antibody titer is < or = 640, the remnant size should be 3 to 5 cm3; if the antibody titer is 1,280 to 2,560, then the remnant size should be 4 to 5 cm3; and if the antibody titer is > or = 5,120, then the remnant size should be around 5 cm3.