TSH: What is it, Test, High and Low
TSH test is an examination that shows how well the thyroid glands are working. Determining whether the thyroid glands are working too much or too little is of great importance in terms of the treatment given to the patient. This test can be performed for control purposes in people who already have a known thyroid disease, or it can be performed for screening purposes and can reveal the thyroid disorder in the person.
What is TSH?
TSH (Thyroid Stimulating Hormone) is a hormone that stimulates the thyroid glands. TSH is released into the blood from a region in the brain called the pituitary. It is very important for the TSH level in the blood to be within normal limits for proper thyroid function.
The TSH test measures the level of the hormone called TSH in the blood. According to the results of this test, it is determined whether the patient’s TSH level is normal or low/high.
What is TSH used for?
TSH, as its name suggests, is a thyroid-stimulating hormone.
The thyroid is a small, butterfly-shaped gland located in the neck. Hormones secreted from the thyroid gland; It affects many areas, from body temperature to muscle strength, from metabolism to mood. Therefore, for a person to be healthy, thyroid hormones must be secreted in sufficient amounts. Secretion of thyroid hormones, more or less than normal, has a negative effect on health.
TSH stimulates the thyroid glands, increasing hormone production and release. There are some feedback mechanisms to maintain the balance between TSH and thyroid hormones. According to these mechanisms, when thyroid hormones are at low levels, TSH is secreted more and increases thyroid hormone production. Conversely, when thyroid hormones are at high levels, it has a reducing effect on the release of TSH from the pituitary. As a result, TSH is high when thyroid hormones are low, and TSH is low when thyroid hormones are high.
What is Low TSH?
Blood TSH levels measured by the TSH test give information about thyroid functions. Although reference ranges for adults vary depending on the method and laboratory measured, TSH values below 0.4 mU/L are generally considered low.
low TSH; It means that the thyroid gland is more active than normal, producing more hormones. This condition, called hyperthyroidism, causes the metabolism to accelerate. Conditions that can cause hyperthyroidism are as follows:
- Graves’ Disease (Toxic Goiter): Graves’ disease is a common disorder in which the thyroid gland becomes excessively enlarged and produces too much hormone. Graves’ disease develops due to the production of thyrotropin receptor antibody (TRAb) as a result of a disorder in the immune system. These antibodies act like TSH and stimulate the thyroid gland, causing the gland to become overactive.
- Thyroiditis: Inflammation of the thyroid gland is called thyroiditis. Thyroiditis causes underactivity of the thyroid gland in the long term. However, when inflammation first begins, hormones from the thyroid gland suddenly mix with the blood, leading to hyperthyroidism.
- Excess Iodine: Iodine is an essential mineral for the production of thyroid hormones. Too much iodine in the body causes the thyroid gland to overwork. Excess iodine accumulation in the body is usually due to long-term use of drugs containing high amounts of iodine. These drugs include some cough syrups and pharmacological agents such as amiodarone, which is used to treat heart arrhythmia.
- Thyroid Nodules: Nodules are lump-shaped structures formed on the thyroid gland. These structures, which are generally benign, can sometimes begin to produce hormones independently of the gland. As a result, hyperthyroidism occurs.
All these situations may cause hyperthyroidism in a person. Symptoms seen in people with hyperthyroidism:
- Weight loss despite eating normally or more
- increased heart rate
- Irregular heartbeat, arrhythmia
- increased appetite
- Irritability, anxiety, restlessness
- Tremors, especially in the hands
- Irregularities in the menstrual cycle
- Increased sensitivity to heat
- Increased bowel movements, need to go to the toilet more often, diarrhea
- Enlargement of thyroid gland size (goiter)
- muscle weakness
- difficulty falling asleep
- thinning of the skin
- Weakening of hair strands, breakage and hair loss
What is TSH High?
If the TSH values measured in the blood sample are more than approximately 4-5 mU/L in adults, it is considered elevated. While the upper limit in children is roughly the same as in adults, values above 3.5-4 mU/L are considered high in pregnant women.
High TSH means low levels of thyroid hormones. TSH rises to increase the level of thyroid hormones. A healthy thyroid responds to this increase and increases hormone production, but when there is a problem in the thyroid gland, an increase in production may not be observed. The condition in which thyroid hormones are low is called hypothyroidism. Situations that may lead to hypothyroidism can be listed as follows:
- Hashimoto’s Disease: Hashimoto’s disease occurs when the immune system incorrectly attacks the thyroid gland. Damage to the thyroid due to disease can prevent the gland from functioning properly, causing hormone production to decrease.
- Thyroiditis: Thyroiditis, which is an inflammation of the thyroid gland, disrupts the functioning of the thyroid gland in the long term and causes hypothyroidism.
- Postpartum Thyroiditis: Some women may experience a temporary decrease in thyroid hormones after giving birth. This condition is called postpartum thyroiditis or postpartum thyroiditis.
- Iodine Deficiency: Since iodine is necessary for the production of thyroid hormones, not enough hormones can be synthesized in iodine deficiency. Iodine deficiency, which was a very common condition in our country in ancient times, has become less common today thanks to the addition of iodine to table salt.
Hypothyroidism has the opposite effects on the body as hyperthyroidism. The symptoms seen in case of hypothyroidism are as follows:
- Getting fat
- slow heart rate
- Memory problems, forgetfulness
- Irregularity in the menstrual cycle, periods that are heavier than normal
- Increased sensitivity to cold
- Enlargement of the thyroid gland (goiter)
- Muscle pain, muscle tenderness and stiffness
- Pain, stiffness, swelling in joints
- Dry skin
- Thinning of hair strands
- facial swelling
- Hoarseness of voice, hoarseness
- Increase in blood cholesterol levels
Things to Know About TSH Test
TSH test is performed by examining a blood sample taken from a vein in the laboratory. There is no need for any preliminary preparation such as fasting for 8-12 hours for the TSH test. However, if the doctor wants to check fasting blood sugar along with TSH, the patient must have been fasting for 8-12 hours before giving blood.
In evaluating thyroid functions, T3 and T4 levels, which are thyroid hormones, are also checked along with TSH. All these values are evaluated together and it is examined whether there is a problem with the person’s thyroid functions.
Some conditions can affect the results of a TSH test. A few of these situations are as follows:
- When the Test was Done: The TSH value obtained as a result of the test performed after long-term fasting may be slightly higher than the test performed during satiety.
- Health Status: Acute or chronic disease can create stress on the endocrine system, including the thyroid gland, causing the results to deviate.
- Medicines: Some types of drugs used in the treatment of arrhythmia and cancer, Non-Steroidal Anti-Inflammatory Drugs (NSAIDs); It may affect TSH test results.
Thyroid hormones are very effective on body metabolism. Therefore, a change in the levels of these hormones affects the entire body. People with thyroid disease must go for a check-up on the dates determined by their doctor and have the necessary TSH and other necessary tests done. Healthy people should also have their thyroid functions checked at regular intervals. Both hyperthyroidism and hypothyroidism can lead to serious health problems if left untreated. For this reason, people with a thyroid-related disorder should not interrupt their treatment.