Clinical experience with recombinant human thyroid-stimulating hormone (rhTSH): serum thyroglobulin measurement

Only normal or neoplastic thyroid follicular cells produce and secrete the prohormone, thyroglobulin (Tg). For some 25 years, elevated serum concentrations of Tg therefore have been employed as a post-operative marker for well-differentiated thyroid carcinoma. The aim of serum Tg measurement is to identify patients requiring: A) further testing to confirm the presence and to determine the stage, site and functionality of tumour; and/or B) further treatment. Serum Tg testing has the advantages of superior sensitivity to radioiodine whole-body scanning (WBS), lack of false positive readings, simplicity, speed, low cost, precision and wide availability. However, major limitations of serum Tg testing are interference by serum anti-Tg antibodies and decreased sensitivity during THST. To obviate this last drawback, the use of recombinant human thyroid-stimulating hormone (rhTSH) has been clinically investigated as a preparative adjunct to serum Tg testing in the diagnostic follow-up of well-differentiated thyroid cancer. A large, multicentre international Phase III study now has confirmed evidence from earlier Phase I/II and Phase III trials and established the safety and efficacy of rhTSH in stimulating Tg release by residual and neoplastic thyroid tissue. This confirmatory study has clearly shown that 1) rhTSH administration significantly increases sensitivity of serum Tg measurement in patients on THST; and 2) by permitting sensitive diagnostic follow-up with serum Tg measurement and/or radioiodine WBS during THST, rhTSH administration improves patient comfort and quality of life compared to THST withdrawal. Thus use of the drug in diagnostic follow-up recently has received regulatory approval in the United States, and such approval is pending in the European Union. With regulatory approval, rhTSH is likely to gain an important role as a preparative adjunct to serum Tg testing in everyday practice.