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The large majority of patient with raised TSH and normal free thyroid hormones are suffering from subclinical autoimmune hypothyroidism.
These results occur more rarely in the following circumstances:
- the presence of heterophile antibodies
- mouse antibodies are used in many TSH assays
- patients may have antibodies to mouse immunoglobulins
- heterphile antibodies result in a false TSH elevation
- alternative assays should be used for these patients
- in patients taking a regular dose of thyroxine an increase in the TSH concentration may indicate thyroxine malabsorption, due to:
- small bowel disease
- iron therapy
- recovery from severe non-thyroidal disease
- congenital abnormalities of thyroid function:
- some cases of Pendred's syndrome
Last reviewed 01/2018