Recombinant human TSH (rhTSH) in 2009: new perspectives in diagnosis and therapy

Thyrotropin stimulating hormone (TSH) exerts a physiological stimulus to growth, function and ability to take up iodine of both normal and malignant follicular cells. For this reason, the metastases deriving from well differentiated thyroid cancer (DTC) can be effectively treated with radioiodine but this procedure requires a strong TSH stimulus that can be obtained by withdrawing the L-thyroxine (LT4) therapy. However, both the social and personal life of patients while they are withdrawing the LT4 therapy are heavily affected by hypothyroidism. After more than a decade since the development of recombinant human TSH (rhTSH), this molecule has been introduced in the clinical practice (1998 in USA and 2001 in Europe) as a safe and reliable alternative to LT4 withdrawal. For several years the main clinical application of rhTSH was for diagnostic purposes (i.e. thyroglobulin stimulation) but, after the more recent demonstration of its efficacy in preparing DTC patients for radioiodine post surgical thyroid remnant ablation, also this application has been officially recognized worldwide. The validity of rhTSH has been also demonstrated in stimulating metastatic thyroid cancer cells but this employment is not yet officially approved and it can be used only in patients with contraindication to hypothyroidism (i.e. "compassionate use"). Other possible uses of rhTSH stimulation are related to its ability to enhance both 18FDG uptake during PET scan of metastatic DTC patients and the effectiveness of conventional chemotherapy. The aim of this review was to recall how the rhTSH has been developed and progressively introduced in the clinical management of DTC patients.