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Remnant thyroid tissue after thyroidectomy alters hormone balance
Ito M, et al. Eur J Endocrinol. 2015;doi:10.1530/EJE-15-0138.
August 20, 2015
The presence of remnant thyroid tissue after a thyroidectomy in adults shifts the hormonal balance between free thyroxine, free triiodothyronine and thyroid-stimulating hormone, according to research in the European Journal of Endocrinology.
Mitsuru Ito, MD, of the Center for Excellence in Thyroid Care at Kuma Hospital, Kobe, Japan, and colleagues analyzed data from 253 patients with papillary thyroid carcinoma who underwent a total thyroidectomy or hemithyroidectomy between October 2011 and February 2013 and were followed for at least 18 months. Within the cohort, 103 patients underwent a total thyroidectomy plus levothyroxine therapy; 56 underwent a hemithyroidectomy plus levothyroxine therapy; 94 underwent hemithyroidectomy alone; 951 euthyroid patients who were examined but did not have signs of thyroid disease served as controls.
Researchers compared postoperative serum levels of free T₄ and free T3, as well as the free T3 to free T₄ ratio in individual patients with controls matched by serum TSH levels.
Researchers found that patients who underwent a total thyroidectomy plus levothyroxine therapy had higher free T₄ levels (P < .001), lower free T3 levels (P < .01) and lower free T3 to free T₄ ratios (P < .001) when compared with controls. The hemithyroidectomy plus levothyroxine therapy arm had free T3 and free T4 levels similar to controls, whereas the hemithyroidectomy without levothyroxine arm had lower free T4 (P < .01), similar free T3 and higher free T3 to free T4 ratios (P < .001) than controls.
“The results of the present study demonstrate that in patients who underwent [total thyroidectomy] and showed normal TSH levels postoperatively, the postoperative serum [free] T₃ levels were lower than their preoperative native levels and those of the matched euthyroid controls despite the increased [free] T₄ levels,” the researchers wrote. “These data suggest that TSH-suppressive doses of levothyroxine are required to achieve normal [free] T₃ levels in patients who have undergone [total thyroidectomy] not only for thyroid cancer, but also for other diseases such as Graves’ disease, multinodular disease and Hashimoto thyroiditis.” – by Regina Schaffer