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About the test
What is this test done for?
The test evaluates levels of the thyroid stimulating hormone (TSH) of the blood. TSH is produced by a small gland called pituitary, located at the base of the brain.
Why is it Done?

The test is carried out to:

  • Rule out hypothyroidism
  • Rule out hyperthyroidism

TSH levels help in confirming the diagnosis of hypothyroidism as well as hyperthyroidism and in assessing their severity. TSH is done singularly as a basic screening test for thyroid function. TSH test, along with other tests of the thyroid panel / thyroid profile, helps in accurate diagnosis of underlying thyroid or pituitary disease.

When should it be performed?

This test is performed when a person has:

  • Symptoms of hypothyroidism such as:
    • Obesity
    • Easy fatigability
    • Constipation
    • Increased sensitivity to cold
    • Weight gain
    • Puffy face, especially in the morning
    • Dry skin
    • Muscle weakness
    • Pain, stiffness and swelling of joints
    • Irregular menstrual periods
    • Thinning of hair
    • High levels of cholesterol in blood
    • Slow heart rate
    • Impaired memory or depression.
  • Symptoms of hyperthyroidism such as:
    • Sudden weight loss
    • Increased appetite
    • Rapid heart beat
    • Tremors (fine trembling of hands and fingers)
    • Increased sweating (hyperhidrosis)
    • Increased bowel frequency
    • Increased sensitivity to heat
    • Changes in menstrual pattern
    • Nervousness, anxiety and irritability
    • Fatigue and muscle weakness
    • Thin and brittle hair.
  • In patients of existing thyroid disorder, the test is done regularly to monitor the course of treatment.
  • History of post-partum thyroiditis
  • Those undergoing radiation therapy for cancer of head, face, or neck
  • Rheumatoid arthritis patients undergoing treatment with amiodarone or lithium, then 6-12 months during treatment and 12 months after the treatment
How is it done
A blood sample will be collected from a vein in your arm. No special preparations like fasting required.

The test result is normal if TSH levels are 0.5-5.0 mU/L.

It means either of the following:

  • Absence of any thyroid disease (called euthyroidism)
  • Adequate thyroxine dose for treating hypothyroidism
  • Adequate therapy of hyperthyroidism.

If TSH levels are above 10 mU/L (high); and corresponding free T4 levels are below 5.0 pmol/L (low), it indicates either of the following:

  • Hypothyroidism
  • Poorly controlled hypothyroidism, or
  • Over controlled hyperthyroidism

If TSH levels are below 0.5 mU/L (low); and corresponding free T4 levels are above 25.0 pmol/L (high), it indicates either of the following:

  • Hyperthyroidism
  • Poorly controlled hyperthyroidism
  • Over controlled hypothyroidism

If TSH levels are between  5 - 10 mU/L and Free T4 levels are 9.0-25.0 pmol/L; it means subclinical hypothyroidism. i.e. no symptoms

If TSH levels are below 0.5 mU/L (low) and Free T4 levels are below 9 pmol/L (low); it means either of the following:

  • Hypopituitarism
  • Secondary hypothyroidism
  • Response to a significant non-thyroid illness

If Free T3 levels are above 8 pmol/L (high), it means hyperthyroidism. If Free T3 levels are very high, it means severe form of hyperthyroidism.

Other Tests

Other tests that can be done after TSH is tested include:

  • Thyroid panel test/ Thyroid profile: which has T3, T4, free T3, and free T4 along with TSH.
  • Anti TPO antibodies
    • Presence of Anti TPO antibodies suggest the cause of hypothyroidism as autoimmune thyroiditis
  • TRAb (TSH receptor antibodies)
    • This is a specific test for ruling out Grave’s disease
  • Thyroglobulin antibodies
    • This test is done for checking antibodies against thyroglobulin
    • It indicates the cause of thyroid disease as Hashimoto’s thyroiditis or idiopathic myxedema.
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