The TSH normal range may vary from lab to lab. 

The TSH normal range for different age groups is given below:

Patients (Age)                                            TSH Normal Range

• If your TSH level is increased, it usually indicates that you have hypothyroidism. Hashimotos thyroiditis is the most common cause of primary hypothyroidism. 
• If your TSH level is decreased, it usually indicates hyperthyroidism. Graves disease, multinodular goiter, toxic nodule are some of the common causes of hyperthyroidism. 

Note: TSH normal range levels show circadian variation (fluctuates during the 24-hour cycle), reaching peak levels between 2-4 am and are at a low between 6-10 pm.

Thyroid Stimulating Hormone (TSH) test measures the amount of TSH in your blood which helps to find out if the thyroid gland is working normally or not. Low TSH levels indicate hyperthyroidism and high TSH levels indicate hypothyroidism.

In case of hyperthyroidism, the thyroid gland produces very high amounts of thyroid hormones (T3 and T4) and you may experience symptoms of weight loss, rapid heartbeat, tremors, sweating, anxiety, increased sensitivity to heat etc. In case of Hypothyroidism, there is a decreased production of thyroid hormones (T3 and T4) which may cause symptoms like weight gain, fatigue, slow heart rate, increased sensitivity to cold, depression, dry and thin hair etc.

There is a feedback system in the body to maintain stable amounts of the thyroid hormones (T3 and T4) in the blood. TSH signals the thyroid gland to make and release the thyroid hormones (T3 & T4) into the blood when the level of thyroid hormones is low and can also signal the thyroid gland to lower the production of thyroid hormones when the level of thyroid hormones is very high. So, when the thyroid hormone (T3 and T4) levels decrease, the pituitary gland is stimulated to release TSH and this high TSH levels, in turn, stimulates thyroid gland to release more thyroid hormone (T3 & T4) from the thyroid gland and the vice-versa happens when the thyroid hormone levels are very high.

Hyperthyroidism is a condition in which the thyroid gland is overactive and there is an increased production of thyroid hormones by the thyroid gland. Causes of Hyperthyroidism include Graves disease, multinodular goiter, thyroid nodules, toxic adenoma, inflammation of the thyroid, eating too much iodine, and too much synthetic thyroid hormone. Diagnosis of this condition can help to relieve the symptoms and prevent long term complications.

Symptoms of Hyperthyroidism include: n nRapid heartbeat (tachycardia) commonly more than 100 beats/minute irregular heartbeat (arrhythmia) or pounding of your heart (palpitations), sudden weight loss, nnervousness, anxiety, irritability, tremor (usually a fine trembling in your hands and fingers), nchanges in menstrual patterns, increased sensitivity to heat, changes in bowel patterns (especially more frequent bowel movements), nan enlarged thyroid gland (goiter) which may appear as a swelling at the base of your neck, increased appetite, sweating, fatigue, muscle weakness, sleep disturbances, skin thinning, fine and brittle hair

Hypothyroidism, also called underactive thyroid or low thyroid is a condition in which the thyroid gland does not produce enough thyroid hormones. It can be commonly caused by intake of low iodine diet or Hashimoto's thyroiditis (an autoimmune disease). Less common causes include previous treatment with radioactive iodine, injury to the pituitary gland which secretes TSH, intake of certain medicines, previous thyroid surgery or a lack of a functioning thyroid gland at birth.

Symptoms of Hypothyroidism include:nTiredness (fatigue), constipation, feeling cold, dry skin, weight gain, muscle weakness, decreased sweating, depression, slowed heart rate, increased blood cholesterol levels, pain and stiffness in your joints, impaired memory, problems of infertility or menstrual changes, muscle stiffness, aches, and tenderness, hoarseness, puffy face, dry and thin hair

Inform the doctor if you are taking any medicine or herbal product as some medicines like birth control pills, estrogen, Lithium, Prednisone, Amiodarone etc. might interfere with the test results. A recent X-ray with iodine dye (contrast) or test using radioactive materials may also affect the results. Moreover, TSH levels show circadian variation (fluctuates during the 24 hour cycle) hence sample for TSH test should be given at the same time in follow up cases.

If the TSH levels are not in the normal range, your doctor may ask for the following tests to establish the diagnosis of a suspected disease:nT4 thyroid hormone test, T3 thyroid hormone test, Thyroid Hormone Binding Globulin (THBG) test, and Thyroid profile.

This test is performed on a blood sample. A syringe with a fine needle attached is used to withdraw blood sample from a blood vessel in your arm generally from the inner side of the elbow area. The doctor, nurse or the phlebotomist will tie an elastic band around your arm which will help the blood vessels to swell with blood and hence makes it easier to withdraw blood. You may be asked to tightly clench your fist. Once the veins are clearly visible, the area is cleaned with an antiseptic solution and then the needle is inserted into the blood vessel to collect the sample. You may feel a tiny pinprick during the procedure. Blood sample once collected is then sent to the laboratory.

There is no risk associated with the test. However, as this test involves a needle prick to withdraw the blood sample, rarely, a patient may experience increased bleeding, hematoma (blood collection under the skin) formation, bruising or infection at the site of needle prick.

An untreated hyperthyroidism during pregnancy can lead to miscarriage, premature birth, low birth weight, preeclampsia (a very high rise in blood pressure in late pregnancy), thyroid storm (a sudden, severe worsening of symptoms of hyperthyroidism) and congestive heart failure.

An untreated hypothyroidism during pregnancy can cause preeclampsia (a very high rise in blood pressure in late pregnancy), anemia, miscarriage, low birthweight, stillbirth (death or loss of a baby before or during delivery) and rarely congestive heart failure. These problems occur most often with severe hypothyroidism.nAs the thyroid hormones play an important role in the development of babys brain and nervous system, untreated hypothyroidismespecially during the first trimestercan cause low IQ and other problems with normal development.

Congenital hypothyroidism is an important cause of elevated thyroid-stimulating hormone (TSH) in newborns. Other causes of an elevated TSH include transient hypothyroidism due to neonatal illness, premature birth, iodine excess or deficiency. High TSH can also be seen in case the mother is taking some medicines that could affect thyroid hormone levels or the mother has some underlying thyroid disease.