TSH – Thyroid-stimulating hormone is a hormone that regulates thyroid function
TSH or thyroid-stimulating hormone is secreted by the pituitary gland. TSH is tested when examining thyroid function.
Thyroid-stimulating hormone (TSH)
- TSH is essential for the production of the thyroid hormone, thyroxine.
- Thyroid-stimulating hormone is the first test that is carried out when examining thyroid function.
- TSH can be tested due to symptoms of fatigue, for example.
Table of contents
What is thyroid-stimulating hormone (TSH)?
TSH or thyroid-stimulating hormone is secreted by the pituitary gland. Thyroid-stimulating hormones are tested when examining thyroid function. Thyroid-stimulating hormone is essential for the production of the thyroid hormone, thyroxine.
The thyroid affects the functioning of the whole body. It regulates metabolism, affects our energy levels and mood, and much more.
The level is the primary investigation when suspecting thyroid underactivity or overactivity. Symptoms of these conditions include changes in weight, fatigue, low or high blood pressure, and mood changes.
High TSH value
A high value may indicate the following conditions:
- Primary hypothyroidism. The concentration may increase as early as in the subclinical state. Subclinical means that the hypothyroidism is latent.
- Autoimmune thyroiditis or Hashimoto’s disease An inflammation of the thyroid gland in which T and B lymphocytes accumulate in the thyroid gland.
- Acute infection or illness.
- Age. People over the age of 65 may have higher TSH levels.
- Secondary hyperthyroidism. A condition in which hyperthyroidism is caused by damage to the hypothalamus or hypophysis.
- Heterophile antibodies. Treatment with thyroxine will not help, the cause of the symptoms requires further examination.
Low TSH value
A low value may indicate the following conditions:
- Primary hyperthyroidism. TSH is decreased because there is too much T3 and T4 in the blood.
- Secondary or tertiary hypothyroidism. In other words hypothyroidism caused by the hypothalamus or the pituitary gland. The thyroid hormone production is also low.
- Nodular thyroid disease.
- Treated Basedow’s disease. Treatment of hyperthyroidism with medication, surgery or radioactive iodine therapy usually leads to hypothyroidism.
- Toxic thyroid adenoma. A benign nodule that produces too much thyroid hormone.
When is TSH measured?
TSH level in the blood is examined to diagnose hyperthyroidism and hypothyroidism, as well as to evaluate the effectiveness of thyroid hormone replacement therapy. Thyroid-stimulating hormone can also be measured when the thyroid’s health needs to be investigated.
If there is a genetic predisposition to thyroid disease, it is advisable to measure the levels in a timely manner.
Fatigue, weight gain, and other symptoms associated with thyroid overactivity or underactivity are good reasons to measure TSH levels.
Blood tests are conducted regularly during thyroxine treatment to ensure its effectiveness. For investigating thyroid disorders, TSH measurement is primary but not the only test.
If TSH level is outside the reference values, determining free T4 hormone levels is necessary. Thyroid-stimulating hormone is highly sensitive to changes in thyroxine hormone levels.
In the following cases, the examination of TSH does not yield a reliable result:
- people with central hypothyroidism caused by the pituitary gland
- hospitalised patients taking TSH-lowering drugs (dopamine, glucocorticoids)
- people whose substitution or suppression therapy is changed
- people with acute psychiatric illness
FAQ
Hypothyroidism is treated with thyroxine replacement therapy, which means that the patient is given synthetic thyroxine (T4) to replace the missing hormone. The treatment is adjusted individually to the patient’s needs, and the effectiveness of the treatment is monitored with regular blood tests that measure the levels of thyroid hormones. The treatment is usually lifelong.
A thyroid test is taken when there is a suspicion of thyroid dysfunction or to monitor an already diagnosed thyroid disease.
Thyroid levels can change in a few weeks, but usually, the changes occur more slowly, over months.
A thyroid test is taken as a blood test.
Hypothyroidism usually develops slowly, often over several years.
Hypothyroidism can cause symptoms such as fatigue, weight gain, intolerance to cold, constipation, and dry skin.
Thyroid medication is usually started when laboratory tests show abnormalities in thyroid hormone levels and the patient has symptoms.
The results of thyroid tests are usually available the 1-2 business days.
The frequency of thyroid tests depends on the patient’s situation. Typically, follow-up tests are done every 6-12 months, but they can be done more frequently to assess the response to treatment.
Hyperthyroidism is diagnosed in the same way as hypothyroidism: with blood tests that measure the levels of TSH and free T4. In hyperthyroidism, TSH is low and free T4 is high.
Thyroid disorders can cause a variety of symptoms such as fatigue, weight changes, mood swings, dry skin, and hair loss.
Hypothyroidism is diagnosed with blood tests that measure the levels of TSH and free T4. If TSH is elevated and free T4 is low, it indicates hypothyroidism.
The effects of thyroxine can start to appear within a few days, but the full effects may not be evident until several weeks or months later. This depends on various factors, such as dosage and individual differences in thyroid function.
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