Dynamic thyroid stimulating hormone tests: do they still have a role?

Modern assays for TSH and for free thyroid hormones have significantly reduced the need for dynamic testing of the hypothalamo-pituitary-thyroid axis in patients with biochemical thyroid dysfunction. However, under certain conditions, such as isolated TSH deficiency, thyrotropinoma and thyroid hormone resistance, the TRH test remains an important adjunctive diagnostic tool. In recent years, the development of recombinant human TSH (rhTSH) has led to a new dynamic test of thyroglobulin (Tg) secretion as a marker of recurrent or metastatic thyroid cancer. RhTSH provides an alternative to thyroid hormone suppression treatment withdrawal in patients who cannot tolerate hypothyroidism and is the agent of choice in patients unable to mount a TSH response.