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Causes of high and low free thyroxine
Medical expert of the article
Alexey Kryvenko, Medical Reviewer, Editor
Last reviewed: 04.07.2025
Last reviewed: 04.07.2025
Diseases and conditions in which the concentration of cT4 ( thyroxine) in the blood serum changes
Increased concentration
- Hyperthyroidism
- Acute thyroiditis
- Pregnancy
- Obesity
- Hepatitis
- Use of estrogens (oral contraceptives), thyroid drugs, heparin, imidazole derivatives
Decreased concentration
- Hypothyroidism (myxedema)
- Increased protein loss (renal syndrome)
- Itsenko-Cushing syndrome
- Androgen intake
- Severe iodine deficiency
- Physical activity
- Panhypopituitarism
- Protein loss through the gastrointestinal tract
- Use of glucocorticosteroids, reserpine, sulfonamides, penicillin, potassium iodide
- Thyroid resection
- Thyroid cancer
- Antithyroid drug overdose