What is thyrotropin?

Thyrotropin, or the thyroid stimulating hormone (TSH) is produced by the pituitary, its release is generally minimal in the morning and higher in the late evening. Thyrotropin promotes the growth of the thyroid gland in the neck and stimulates it to produce more thyroid hormones. When there is an excessive amount of thyroid hormones, the pituitary gland stops producing TSH, reducing thyroid hormone production. TSH causes the thyroid gland to make two hormones: triiodothyronine (T3) and thyroxine (T4) by the thyroid gland, which is a small gland found in the neck area appointed with regulating metabolic process in the human body. T3 and T4 help control your body's metabolism. Triiodothyronine (T3) and thyroxine (T4) are needed for normal growth of the brain, especially during the first 3 years of life. A baby whose thyroid gland does not make enough thyroid hormone (congenital hypothyroidism) may, in severe cases, be mentally retarded. Older children also need thyroid hormones to grow and develop normally.


Why measure the level of thyrotropin?

This test allows us to evaluate the levels of TSH and consequently the proper thyroid function. Often this examination is prescribed in combination with a FT4 and a FT3 examination. This test is also prescribed to find out whether the thyroid gland is working properly. An underactive thyroid gland (hypothyroidism) can cause symptoms such as weight gain, tiredness, dry skin, constipation, a feeling of being too cold, or frequent menstrual periods. An overactive thyroid (hyperthyroidism) can cause symptoms such as weight loss, rapid heart rate, nervousness, diarrhea, a feeling of being too hot, or irregular menstrual periods. It is also used to find the cause of an underactive thyroid gland, as the TSH levels can help determine whether hypothyroidism is due to a damaged thyroid gland or due to other causes. It is also used to keep track of treatment with thyroid replacement medicine for people who have hypothyroidism, and keep track of thyroid gland function in people who are being treated for hyperthyroidism. This treatment may include antithyroid medicine, surgery, or radiation therapy. It is also used to double-check the diagnosis of an underactive thyroid gland in a newborn (congenital hypothyroidism).

Normal values range from 04 to 4.0 mlU/L. However these vary depending on the laboratory and method used.


Standard of preparation

Sampling is usually done in the morning in the hospital. There are no special preparations needed for this test. The doctor will advise and recommend if you need to be fasting prior to the blood examination. You should inform your doctor of any medication you are taking prior to the exam, as some medical treatments may interfere with the blood results.


Is the examination painful or dangerous?

The examination is neither painful nor dangerous. The patient may feel a tingling sensation with the entrance of the needle in the arm when blood is being extracted for examination.


How is the exam performed?

The exam consists of a simple blood sample test.