Influence of the endogene TSH stimulation of thyroid volume increase in the patients after total thyroidectomy due to differentiated thyroid cancer

The treatment-of-choice for differentiated thyroid carcinoma (DTC) is a total thyroidectomy with subsequent radioiodine therapy. In order to increase an iodine uptake in thyroid tissue remnants, the L-thyroxine withdrawal is required. It is recommended to achieve TSH levels higher than 25 mU/ml. As TSH is a known key factor in thyroid cell proliferation regulation, prolonged stimulation of the cells during L-thyroxine withdrawal can be a causative factor for a re-growth. Our aim was to assess the degree of thyroid re-growth in the patients after total thyroidectomy due to DTC and its possible clinical implications. 23 patients operated due to papillary and follicular thyroid cancer were included into the study. Biochemical determinations and ultrasound thyroid imaging were performed (TSH, Tg) during suppressive L-thyroxine therapy as well as 4-5 weeks after the withdrawal. The mean volume of thyroid tissue remnants increased after withdrawal for substantial 30.1%. The difference was extremely significant. L-Thyroxine withdrawal in the patients after total thyroidectomy due to DTC can cause re-growth of the tissue remnants. The phenomenon may be of a clinical significance in the selected cases influencing therapeutic decisions.