Thyroid stimulating hormone (TSH) test is a blood test used to evaluate the functioning of the thyroid gland. This test measures the level of TSH, a hormone that regulates hormone production by the thyroid gland, which is under the control of the hypothalamus and pituitary gland. TSH is a signal sent to the thyroid gland and encourages the thyroid gland to produce more or less thyroid hormone. The TSH test is used to evaluate the function of the thyroid gland, to determine whether the thyroid gland is overactive or underactive, or to diagnose thyroid diseases.
TSH is the abbreviation for thyroid stimulating hormone. Thyroid-stimulating hormone is a hormone produced by the pituitary gland and regulates the functioning of the thyroid gland. TSH signals the thyroid gland to produce the hormones thyroxine (T4) and triiodothyronine (T3). TSH levels show how active the thyroid gland is.
If TSH levels are high, it means that the thyroid gland is not active enough. This condition is called hypothyroidism. If TSH levels are low, it means the thyroid gland is too active. This condition is called hyperthyroidism. People with high or low TSH should consult their doctor. The doctor can perform further tests to determine the cause of the TSH level and plan appropriate treatment. Factors that can affect the TSH level include:
- TSH levels increase with age.
- TSH levels are higher in women than in men.
- TSH levels rise during pregnancy.
- Some medications can affect TSH levels.
- Thyroid gland diseases can affect TSH levels.
What is the TSH test?
The TSH (Thyroid Stimulating Hormone) test is a blood test used to evaluate the function of the thyroid gland. It is known that the thyroid gland has the task of producing and secreting hormones that regulate body metabolism. The TSH test plays an important role in diagnosing and monitoring thyroid diseases and whether thyroid functions are normal.
The TSH test is used to diagnose thyroid diseases such as hyperthyroidism, in which the thyroid gland is overactive, or hypothyroidism, in which the thyroid gland is underactive. This test can also be used to monitor whether thyroid diseases are being treated and whether thyroid hormones are being properly regulated during treatment.
What causes low TSH?
Low TSH means the thyroid gland is too active. This condition is called hyperthyroidism. There may be many reasons for low TSH. The most common causes are:
- Graves’ disease: Graves’ disease is an autoimmune disease of the thyroid gland. In this disease, the immune system attacks the thyroid gland and increases the production of thyroid hormones.
- Thyroid nodule: Thyroid nodule is a swelling in the thyroid gland. Some thyroid nodules may increase the production of thyroid hormones.
- Thyroiditis: Thyroiditis is inflammation of the thyroid gland. Thyroiditis can increase the production of thyroid hormones.
- Medicines containing thyroid hormone: Some medications contain thyroid hormones. These medications may lower TSH levels.
- Pregnancy: During pregnancy, the placenta produces hormones that lower TSH levels.
- Iodine deficiency: Iodine is a mineral necessary for the production of thyroid hormones. Iodine deficiency can reduce the production of thyroid hormones and increase TSH levels.
People with low TSH should consult their doctor. The doctor can perform further tests to determine the cause of the TSH level and plan appropriate treatment. Some symptoms may occur in people with low TSH. Symptoms of low thyroid:
- Losing weight
- Irritability
- Insomnia
- excessive sweating
- heart palpitations
- tremors in hands
- Defecation irregularities
- muscle weakness
- Hair loss
- skin dryness
How low is TSH dangerous?
Low TSH means that the thyroid gland produces more thyroid hormone than normal. TSH levels 0.4mU/LIf it is below, it is considered low TSH. If you experience symptoms of low TSH such as heart palpitations, tremors in your hands, nervousness, insomnia, excessive sweating, diarrhea or constipation, hair loss, dry skin and muscle weakness, you should definitely see a doctor. TSH levels 0.1mU/LIf it is below , it is considered severe hyperthyroidism. In this case, the following problems may occur:
- Thyroid storm: Thyroid storm is a life-threatening condition caused by overproduction of thyroid hormones.
- Heart attack
- Stroke
- permanent heart damage
Treatment of low TSH depends on the underlying cause. Antithyroid medications are used in people with Graves’ disease. People with thyroid nodules or thyroiditis may require surgery or radioactive iodine treatment. In people using medications containing thyroid hormone, the dosage of these medications may need to be reduced or changed.
What does low TSH do to the body?
Low TSH means that the thyroid gland produces more thyroid hormone than normal. Thyroid hormones are essential for many body functions such as metabolism, growth and development. Low TSH can cause excessive production of these hormones, leading to the following changes in the body:
- Metabolism accelerates: Thyroid hormones accelerate metabolism. In case of low TSH, the metabolism works too fast, causing weight loss, heat intolerance and sweating.
- Heart rate increases: Thyroid hormones accelerate the heart rate. In case of low TSH, the heart rate may run too fast, causing palpitations and irregular heartbeats.
- Muscle weakness occurs: Thyroid hormones are necessary for the normal functioning of muscles. In case of low TSH, muscles may weaken, causing weakness and fatigue.
- Irritability and restlessness occur: Thyroid hormones stimulate the central nervous system. In case of low TSH, irritability, restlessness and insomnia may occur.
- Hair loss occurs: Thyroid hormones support hair growth. In case of low TSH, hair loss may occur.
- Skin dries: Thyroid hormones keep the skin moisturized. In case of low TSH, the skin may become dry.
What is the TSH value and should the medication be started?
Treatment is started immediately in people with a TSH value below 0.1 mU/L. In this case, antithyroid medications or radioactive iodine treatment can be used. For people whose TSH value is below 0.4 mU/L, the doctor decides on treatment. Treatment depends on the underlying cause. Antithyroid medications are used in people with Graves’ disease. People with thyroid nodules or thyroiditis may require surgery or radioactive iodine treatment. In people using medications containing thyroid hormone, the dosage of these medications may need to be reduced or changed.
What happens if T3, T4 are normal and TSH is low?
If TSH is low while T3 and T4 hormones are normal, this condition is called subclinical hyperthyroidism. Subclinical hyperthyroidism is a condition in which the thyroid gland produces more thyroid hormones than normal, but these hormones do not reach high levels in the blood. Symptoms of subclinical hyperthyroidism are often mild and may go unnoticed. If left untreated, subclinical hyperthyroidism can lead to the following problems:
- Heart disease
- Osteoclasis
- osteoporosis
- eye problems
- thyroid storm
If TSH is low while T3 and T4 hormones are normal, this may be due to one of the following reasons:
- Graves’ disease: Graves’ disease is an autoimmune disease of the thyroid gland. In this disease, the immune system attacks the thyroid gland and increases the production of thyroid hormones.
- Thyroid nodule: A thyroid nodule is a swelling in the thyroid gland. Some thyroid nodules may increase the production of thyroid hormones.
- Thyroiditis: Thyroiditis is inflammation of the thyroid gland. Thyroiditis can increase the production of thyroid hormones.
- Medicines containing thyroid hormone: Some medications contain thyroid hormones. These medications may lower TSH levels.
- Pregnancy: During pregnancy, the placenta produces hormones that lower TSH levels.
- Iodine deficiency: Iodine is a mineral necessary for the production of thyroid hormones. Iodine deficiency can reduce the production of thyroid hormones and increase TSH levels.