The influence of thyroid remnant size, antithyroid antibody titre, thyroid morphology, and lymphocyte infiltration on postoperative thyroid function was studied in 179 patients undergoing subtotal thyroidectomy because of hyperthyroidism. The surgical procedure was strictiy standardized and included determination of the thyroid remnant size. The preoperative medication used was beta-adrenoceptor blocking agents in 101 patients and antithyroid drugs and thyroxine in 78. With remnant size adjusted to 6-10 g (or, in goiters less than 20 g, to 25-30% of initial gland weight), the overall recurrence rate after 2-8 years (mean 5.3 -+ 2.0) of follow-up was 1.7% and the incidence of thyroid hypofunction was 29.6%.In toxic nodular goiter (TNG; n = 63), a significant negative correlation was found between TSH and remnant size after 12 months as well as a significantly lower remnant weight in patients developing postoperative hypothyroidism. In toxic diffuse goiter (TDG; n = I16), there was no difference in remnant size between euthyroid and hypothyroid patients. For patients with TDG treated preoperatively with beta-blockers, the incidence of autoantibodies against thyroid cytoplasm was increased in patients who postoperatively developed thyroid dysfunction. Within the group of TDG developing hypofunction, we found increased titre of autoantibodies and "presence of lymphoid tissue" more often in patients treated preoperatively with beta-blockers compared to thyrostatics. In toxic nodular goiter, the remnant size was considered the parameter most helpful to the surgeon in predicting postoperative thyroid function.

To analyze the inhibitory effect of thyroxine (T4) on thyroid growth, freshly obtained biopsies of human nontoxic multinodular goiter tissue from 9 patients were transplanted to nude mice. After the implantation period, thyroid growth was stimulated by either hemithyroidectomy (HT) or by administration of the goitrogen propylthiouracil (PTU), with or without simultaneous administration of T4. During the latter period,3H‐thymidine was continuously administered by osmotic minipumps to label replicating cells. After processing of the tissue for autoradiography, the fraction of labeled cells (LI) was calculated. Following HT, the fraction of labeled cells in nontoxic multinodular goiter tissue was 4.8%. T4 significantly reduced the LI to 1.0%. The goitrogen induced transplant growth, the LI varying between 28% and 61% in the different specimens. Administration of T4 resulted in lower LI in all transplants: in 5 specimens the LI was similar to control transplants. In transplants from 3 goiter specimens, however, significantly higher LI were found. The present results show that administration of T4 significantly inhibits growth of human thyroid tissue. The effect seems, however, to vary in different specimens of nontoxic goiter, indicating a varying degree of autonomous replicating activity.

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