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The causes of increase and decrease of thyroxine
Last reviewed: 19.10.2021
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Most of the patients with symptomatic hyperthyroidism content of T 4 (thyroxine) is increased and decreased in hypothyroidism blood. However, in some cases, the concentration of T 4 (thyroxine) in the blood does not reflect the functional status of the thyroid gland. These include the conditions under which the concentration of TSH changes. For example, the concentration of T 4 (thyroxine) in the blood can be increased by increasing TSH. The latter may be due to a genetically determined increase in the content of TSH, as well as pregnancy, reception of contraceptives containing estradiol derivatives, estrogen therapy. At the same time, the concentration of T 4 in the blood can be reduced by decreasing the binding ability of TSH. This leads to the following pathological conditions: chronic severe liver disease, nephrotic syndrome, genetically determined decrease in TSG synthesis. Androgen therapy also reduces the binding ability of TSH. In the old age of 20% of people with euthyroid status, the concentration in the blood of TSH decreases, which, in turn, leads to a decrease in the level of T 4.
A temporary increase in the concentration of total T 4 (psevdodisfunktsiya thyroid) was observed in almost 20% of patients admitted to a psychiatric hospital. The concentration of total T 4 (thyroxine) can rise in other diseases, is not associated with changes in thyroid function. In such patients, T 4 (thyroxine) usually normalizes after a few days without treatment. In favor of pseudodysfunction of the thyroid gland is indicated by a reduced concentration of total T 3 and a normal TSH content.
Increasing concentrations of total T 4 (and total T 3 ) without signs of hyperthyroidism possible with a rare hereditary disease - generalized resistance to thyroid hormone. Despite an increase in the concentrations of T 4, cT 4, T 3 and free triiodothyronine (cT 3 ), patients have an euthyroid status, and in some even mild hypothyroidism.
Diseases and conditions in which the concentration varies T 4 (thyroxine) in serum
Increase in concentration
- Hyperthyroidism
- Acute thyroiditis
- Pregnancy
- Obesity
- Hepatitis
- The use of estrogens (oral contraceptives), heroin, thyroid drugs
- Hypofunction of the thyroid gland (myxedema)
Reduction in concentration
- Increased protein loss (kidney syndrome)
- Isenko-Cushing syndrome
- Significant deficiency of iodine
- Exercise stress
- Pangypopituitarism
- Loss of protein through the digestive tract
- The use of glucocorticosteroids, reserpine, sulfonamides, penicillin, potassium iodide, androgens