[The clinical use of human recombinant TSH]

The recent cloning of human TSH-beta gene has allowed the production of recombinant human TSH (rhTSH) by recombinant DNA technology in mammalian cells (Chinese hamster ovary cells). Studies aimed at biochemical and biological characterization have shown that rhTSH, unlike pituitary TSH, is highly sialylated and is biological active in stimulating c-AMP accumulation in FRTL-5 cells. Phase I/II and phase III clinical studies have been performed to evaluate the safety and efficacy of rhTSH in stimulating radioactive iodine uptake in patients after total thyroidectomy for differentiated thyroid cancer. In these patients therapy with thyroid hormones is performed to replace hormone production and to suppress TSH-stimulated tumor growth. To detect residual or recurrent cancer, the therapy has to be withdrawn in order to obtain rise in endogenous TSH to perform a total body scan. rhTSH, as a source of exogenous human TSH, has been shown as an additional diagnostic tool in the follow-up of patients with thyroid cancer. Used in patients maintained on thyroid hormone suppressive therapy, rhTSH enhances the sensitivity of serum Tg testing. Although the sensitivity of scans obtained after rhTSH administration is slightly lower than that after thyroid hormone withdrawal, the use of rhTSH avoids the clinical signs and symptom of hypothyroidism and can be used in selected patients.