Rapid increase in volume of the remnant after hemithyroidectomy does not correlate with serum concentration of thyroid stimulating hormone

OBJECTIVE: To study the effect of postoperative thyroxine on the volume of the thyroid remnant after lobectomy for benign nontoxic goitre. DESIGN: Prospective, randomised study. SETTING: University hospital, Sweden. SUBJECTS: 50 consecutive patients who underwent lobectomy for benign non-toxic goitre. INTERVENTIONS: Patients were randomised postoperatively to take thyroxine 0.1 mg or placebo daily. MAIN OUTCOME MEASURES: The median volume of the remaining thyroid lobe measured by ultrasound. Serum concentrations of thyroxine, triiodothyronine (T3) and thyroid stimulating hormone (TSH) were measured preoperatively and 1, 3, 6, 12 months postoperatively. RESULTS: The median volume of the remaining lobe had increased significantly compared with preoperatively by 1 month postoperatively by 30% in the thyroxine group and 25% in the placebo group (p < 0.01). The difference between the groups was not significant. After the first month the volume did not change significantly. In the thyroxine group, the TSH concentration was unchanged and the thyroxine concentration increased significantly throughout the study. In the placebo group there was a significant increase in TSH concentration and a significant decrease in that of thyroxine at all follow-up examinations. CONCLUSIONS: There is a significant increase in the volume of the remaining thyroid 1 month after lobectomy that persisted throughout the first year. Thyroxine given in a dose that kept the serum TSH concentration at the same level as preoperatively did not seem to influence volume changes; consequently we consider that these are caused by factors other than TSH