Levothyroxine replacement therapy after thyroid surgery
N. Verhaert*, V. Vander Poorten*, P. Delaere*, M. Bex** and F. Debruyne*
*Department of Otorhinolaryngology, Head and Neck Surgery, University Hospitals Leuven, Belgium; **Department of Endocrinology, University Hospitals Leuven, Belgium
Postoperative thyroid function; thyroxine replacement therapy; L-T4; thyroid surgery; thyroidectomy
129 - 133
Levothyroxine replacement therapy after thyroid surgery. Introduction and aim : New entities, such as ‘sub- clinical’over- and undersubstitution, are easily diagnosed after thyroid surgery due to improved testing methods, and the incidence of thyroidectomy with lifelong hormone substitution is increasing. Thus, there is a need to review conventional replacement therapy after thyroid surgery. We investigated the adequacy of our thyroid hormone replacement therapy for three months after total-, subtotal-, and hemithyroidectomy using an upper reference limit of thyrotropin (TSH) of 4.6 mU/L. Materials and methods : Eighty-seven patients undergoing thyroidectomy for benign thyroid pathology participated. Levothyroxine (L-T4) treatment began five days after surgery. Preoperatively euthyroid patients received 150 µg L-T4 daily following total thyroidectomy, 100 µg L-T4 after subtotal thyroidectomy, and 50 µg L-T4 after hemithyroidecto- my. Preoperatively hyperthyroid patients received 100 µg L-T4 following total thyroidectomy and 50 µg L-T4 following subtotal thyroidectomy.An average of six weeks after surgery, thyrotropin (TSH) was measured (reference limits 0.15- 4.60 mU/L), and necessary dose adjustments were made. Results: Of the patients who were preoperatively euthyroid, 45% with total thyroidectomy, 42% with subtotal thy- roidectomy, and 17% with hemithyroidectomy required L-T4 dose adjustments. Of the patients who were preoperative- ly hyperthyroid, 60% of those with total thyroidectomy and all of those with subtotal thyroidectomy required L-T4 dose adjustments. Conclusions: To avoid over- and undersubstitution after thyroidectomy, an optimal replacement therapy dose is necessary. A small majority of our preoperatively euthyroid patients received adequate therapy. Endocrinological follow-up six weeks after surgery revealed the need for L-T4 dose adjustments, especially in preoperatively hyperthyroid patients. When the extent of resection was similar for hyperthyroid and euthyroid patients, the same initial dose of L-T4 was justified.
Vol. 2, 2006, 3rd trimester

Levothyroxine replacement therapy after thyroid surgery