TSH stands for thyroid stimulating hormone. A TSH test is a blood test that measures this hormone. The thyroid is a small, butterfly-shaped gland located near your throat. Your thyroid makes hormones that regulate the way your body uses energy. It also plays an important role in regulating your weight, body temperature, muscle strength, and even your mood. TSH is made in a gland in the brain called the pituitary. When thyroid levels in your body are low, the pituitary gland makes more TSH. When thyroid levels are high, the pituitary gland makes less TSH. TSH levels that are too high or too low can indicate your thyroid isn't working correctly.

Other names: thyrotropin test.

You may need a TSH test if you have symptoms of too much thyroid hormone in your blood (hyperthyroidism), or too little thyroid hormone (hypothyroidism).

Symptoms of hyperthyroidism, also known as overactive thyroid, include:

• Anxiety
• Weight loss
• Tremors in the hands
• Increased heart rate
• Puffiness
• Bulging of the eyes
• Difficulty sleeping

Symptoms of hypothyroidism, also known as underactive thyroid, include:

• Weight gain
• Tiredness
• Hair loss
• Low tolerance for cold temperatures
• Irregular menstrual periods
• Constipation

High TSH levels can mean your thyroid is not making enough thyroid hormones, a condition called hypothyroidism. Low TSH levels can mean your thyroid is making too much of the hormones, a condition called hyperthyroidism. A TSH test does not explain why TSH levels are too high or too low. If your test results are abnormal, your health care provider will probably order additional tests to determine the cause of your thyroid problem. These tests may include:

• T4 thyroid hormone tests
• T3 thyroid hormone tests
• Tests to diagnose Graves' disease, an autoimmune disease that causes hyperthyroidism
• Tests to diagnose Hashimoto's thyroiditis, an autoimmune disease that causes hypothyroidism

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