T3 levels in thyroidectomised patients

Thyroxine (T4) therapy using synthetic levothyroxine (L-T4) is the standard of care for patients who had undergone total thyroidectomy. Thyroidal production of triiodothyronine (T3) is absent in postoperative athyreotic patients. Therefore, relative T3 deficiency may be present during postoperative T4 therapy. Ito et al. conducted a retrospective study on 135 patients with papillary thyroid carcinoma who underwent total thyroidectomy. The objective of this study was to compare the circulating levels of T4 and T3 produced by an individual's own thyroid gland with those levels resulting from L-T4 therapy in the same individuals who underwent total thyroidectomy. They also investigated how to achieve the preoperative native serum T3 levels using postoperative L-T4 therapy.

Their study showed that moderate TSH-suppressive doses of L-T4 were required for postoperative athyreotic patients to achieve their preoperative native serum FT3 levels and that they must take L-T4 for the remainder of their lives. Therefore, even if thyroidal dysfunction may be subtle, its long-term effects cannot be overlooked. Ito et al. (2012) European Journal of Endocrinology 167 373-378.

Read the full article at: DOI: 10.1530/EJE-11-1029