Causes for Increased Thyroxine or Free Thyroxine Values (cont.)

• Acute psychosis (esp. paranoid schizophrenia); some patients

• T4 sample drawn 2-4 hr after Synthroid dose

• Struma ovarii

• Pituitary TSH-secreting tumor; some patients

• Certain x-ray contrast media (Telepaque and Oragrafin)

• Acute porphyria; some patients

• Heparin effect (some T4 and FT4 kits)

• Amphetamine, heroin, methadone, and PCP abuse; some patients

• Perphenazine or 5-fluorouracil; some patients

• Antithyroid or anti-IgG heterophil (HAMA*) autoantibodies (some sandwich-method monoclonal antibody kits); occasional patients

• ìT4ì hyperthyroidism

• Hyperemesis gravidarum; about 50% of patients

• High altitudes, some patients

* Human antimouse antibodies.

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