Thyroid cancer: Treatment with thyroid hormone

Abstract

All patients with thyroid cancer must be treated with thyroid hormone after thyroidectomy for correction of surgically induced hypothyroidism and to suppress stimulated growth of persistent or recurrent thyroid cancer by reducing thyroid-stimulating hormone (TSH) levels. TSH mainly controls growth and differentiation of normal thyroid follicular cells. Secreted by the pituitary gland it is a glycoprotein composed of an alpha and a beta subunit (normal serum TSH concentrations: 0.4-4 μU/ml). After binding with its membrane receptor, TSH stimulates follicular cell proliferation and differentiation functions, including iodine uptake, thyroglobulin synthesis and thyroid hormone production. Thyrotropin releasing hormone (TRH) stimulates TSH secretion, increases thyroid hormones (thyroxin, T4) and decreases TSH secretion by means of a feedback mechanism mainly at the pituitary level after local conversion into T3 by the enzyme 5'-deiodinase type 2. The main principles of thyroid hormone treatment and its clinical implications (monitoring and adjustment of hormone dosage to clinical situations, side effects) will be summarized here. © Springer-Verlag Berlin Heidelberg 2001, 2005.