Reduced Free T4
April 24th, 2019
Overview
Reduced T4 with elevated TSH is suggestive of primary hypothyroidism, which normal or reduced TSH may be present with certain conditions or due to false reduction.
Causes of Reduced Free T4
Elevated TSH
- Primary hypothyroidism
Reduced / Normal TSH
- Nonthyroidal illness
- Recent treatment of hyperthyroidism
- Central hypothyroidism
- Congenital TSH or TRH deficiency
False Reduction
- Increased TBG - pregnancy, oral oestrogen, SERMs, hepatitis
- Drugs - aspirin, phenytoin, carbamazepine
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