T4, total, reduced
Last reviewed 06/2021
Conditions associated with decreased T4 include:
- hypothyroidism
- decreased binding proteins: - increased loss eg. nephrotic syndrome - decreased production
- inhibition of binding to proteins: - systemic illness - drugs eg. phenytoin, salicylates, carbamazepine, fenclofenac, corticosteroids
- exogenous T3 therapy
Note that phenytoin may also reduce free T4, apparently by increasing T4 metabolism.