Table 1.

Conditions in which measurement of TSH alone may be misleading.

•Recent treatment for thyrotoxicosis (TSH may remain suppressed even when TH concentrations have normalised)

•Non-thyroidal illness

•TSH assay interference

•Central hypothyroidism (e.g. hypothalamic/pituitary disorders)

•TSH-secreting pituitary adenoma (thyrotropinoma/TSHoma)

•Resistance to thyroid hormone (RTH)

•Disorders of thyroid hormone transport or metabolism

Key: TH, thyroid hormone; TSH, thyroid-stimulating hormone/thyrotropin.