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Causes of thyroid hormone increase and decrease
Medical expert of the article
Last reviewed: 06.07.2025
In hypothyroidism, the thyroid-stimulating hormone increases. The diagnosis is confirmed by low concentrations of free thyroxine (cT4 ), T4 , T3 in the blood. In cases of subclinical mild hypothyroidism, when the level of cT4 and T4 in the blood is within the normal range, identifying an increased content of thyroid-stimulating hormone becomes crucial. A low level of thyroid-stimulating hormone in hypothyroidism indicates pituitary or hypothalamic insufficiency and excludes primarythyroid dysfunction. Determination of thyroid-stimulating hormone is important for monitoring patients with hypothyroidism who receive daily replacement therapy with sodium levothyroxine. By determining the concentration of thyroid-stimulating hormone, the dose of the drug can be optimized.
In hyperthyroidism, the synthesis and secretion of thyroid-stimulating hormone are suppressed. As a result, primary hyperthyroidism (thyroid disease) is characterized by an increased content of thyroid hormones (T 4, T 3 ) in the blood and a deficiency of thyroid-stimulating hormone.
The concentration of thyroid-stimulating hormone increases in thyrotropin-secreting pituitary tumors (in 90% of cases, macroadenomas larger than 10 mm). At the same time, it is necessary to remember that long-term hypothyroidism can lead to pituitary hyperplasia with the formation of a pseudotumor, therefore, all patients, before undergoing surgery on the pituitary gland, need to study the concentration of cT 4. Elevated values of cT 4 indicate a pituitary adenoma, low values indicate hypothyroidism.
Diseases and conditions in which the concentration of thyroid-stimulating hormone in the blood serum changes
Increased thyroid stimulating hormone concentration
- Primary hypothyroidism
- Subacute thyroiditis
- Hashimoto's thyroiditis
- Pituitary tumor
- Ectopic secretion in tumors of the lung, mammary gland
- Endemic goiter
- Inflammation of the thyroid gland
- Condition after iodine therapy
- Thyroid cancer
Decreased thyroid stimulating hormone concentration
- Primary hyperthyroidism
- Hypothalamic-pituitary insufficiency
- Pituitary tumor
- Pituitary gland injury
- Postpartum pituitary necrosis
- Itsenko-Cushing syndrome
- Use of acetylsalicylic acid, heparin, thyroid hormones, glucocorticosteroids
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