Study of hormone replacement therapy following total thyroidectomy in thyroid cancer--with special reference to the analysis of thyroid hormone peripheral effects, using indirect calorimetry]

Peripheral effects of thyroid hormones were examined using an indirect calorimetry in 18 patients with thyroid cancer before and after total thyroidectomy. Peripheral effects of exogenous thyroid hormones in TSH-suppression therapy after thyroidectomy were also studied. The subjects were maintained without hormone replacement for 3 weeks after total thyroidectomy. The ratio of resting energy expenditure to basal energy expenditure (REE/BEE) was determined before operation, before hormone replacement, and 1 and 5 weeks after the beginning of replacement, and the values were compared with changes in the blood thyroid hormone levels. Positive correlations were observed between the changes in endogenous thyroid hormone levels before and after total thyroidectomy and those in REE/BEE (free T3 vs. REE/BEE; r = 0.756, p less than 0.01), suggesting that evaluation of REE/BEE is clinically useful as an index of peripheral effects of thyroid hormones. Five weeks after the beginning of hormone replacement, T4 and free T4 were slightly range, and no enhancement of energy metabolism was noted. From these findings, the post-operative TSH suppression therapy carried out at our department is considered to be justifiable also from the viewpoint of energy metabolism.