What is TSH used for?
TSH stands for thyroid-stimulating hormone, in other words, the hormone that stimulates the thyroid. Produced by the pituitary gland in the brain, it acts on the thyroid, the gland located at the base of the neck. Its hormones, T3 and T4, influence mood, body temperature, weight and even sex life.
TSH is used to regulate the amount of thyroid hormones, T3 and T4 in the blood. When there is too much, the TSH drops to decrease the production of T3 and T4 by the thyroid. Conversely, if there is not enough, it increases to stimulate production.
What are normal TSH values?
TSH is measured by a simple blood test. It is usually between 0.4 and 4 mIU/l in adults, knowing that these levels may vary according to laboratories and techniques (source: Vidal). It is not necessary to be on an empty stomach for the assay; if you are on antithyroid or levothyroxine treatment, it is advisable to have your blood samples taken at the same time so as not to distort the dosage.
In addition, T4, T3 and certain antibodies (anti-TPO) can be measured.
What does high TSH mean?
Thyroid problems can be linked to damage either to the thyroid gland or to the glands that control it and are located in the brain, the hypothalamus or the pituitary gland. When it is linked to an initial thyroid problem, hypothyroidism, by initial thyroid damage, is characterized by high TSH and low thyroid hormones. The body works in slow motion, we are chilly, constipated, anxious, we think less quickly. Weight gain is often observed when we eat less.
Hypothyroidism can cause heart problems, such as too slow a heart rate (called bradycardia), or too low blood pressure.
What does low TSH mean?
Hyperthyroidism is diagnosed when TSH is low and T4 and/or T3 are high. This is called hyperthyroidism, which includes Graves’ disease. We speak of mild or asymptomatic hyperthyroidism when only the TSH is low, without clinical symptoms.
The body is then in “hyperfunction”: the heart beats faster, breathing accelerates, we lose weight while we eat more. The digestion is too fast, we have diarrhea, we tremble and we have mood disorders, with great nervousness. We are often hot. Heart involvement may also occur, most commonly in the form of tachycardia and palpitations, or increased blood pressure or “sometimes atrial fibrillation” (heartbeat becomes erratic).
How are hypothyroidism and hyperthyroidism treated?
Hypothyroidism is treated by providing levothyroxine, between 100 and 150 micrograms per day in adults. This is called replacement therapy or hormone replacement therapy, which is recommended from a TSH above 10 mIU/l. Treatment is continued for life. Due to an increased need for TSH, the management of pregnant women is specific: treatment may be justified only if the TSH is greater than 4 mIU/L.
Hyperthyroidism is treated with synthetic antithyroid drugs, such as carbimazole, thiamazol or propylthiouracil. After obtaining a normal TSH, which can take several weeks, treatment is continued for 12 to 18 months in Graves’ disease. A recurrence may occur, hence the importance of monitoring for 2 to 3 years. In the event of relapse, large goiter or planned pregnancy (treatment taking place before pregnancy), surgery or treatment with radioactive iodine may be indicated.
If the TSH abnormality is linked to thyroid cancer, Haschimoto’s thyroiditis or so-called central hypothyroidism (when the TSH is low or normal), special care is necessary.
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