TSH ( Thyroid Stimulating Hormone )

A TSH (Thyroid Stimulating Hormone) blood test measures the amount of TSH in your blood and is the most important test for checking thyroid function.

What is TSH?

TSH is a hormone made by the pituitary gland in the brain. Its job is to control the thyroid gland by telling it how much thyroid hormone (T3 and T4) to produce.

Why is the TSH test done?

The TSH test is used to:

• Diagnose thyroid disorders

• Check for hypothyroidism (underactive thyroid)

• Check for hyperthyroidism (overactive thyroid)

• Monitor people taking thyroid medication

• Investigate symptoms such as:

  • Tiredness or weakness

  • Weight gain or weight loss

  • Hair loss

  • Feeling too cold or too hot

  • Fast or slow heartbeat

  • Menstrual changes

Understanding TSH levels

• High TSH: Usually means the thyroid is not making enough hormones (hypothyroidism)

• Low TSH: Usually means the thyroid is making too much hormone (hyperthyroidism)

• Normal TSH: Indicates normal thyroid function

(Normal range may vary slightly by laboratory, but is usually around 0.4–4.0 mIU/L.)

How is the test done?

• A blood sample is taken from a vein in the arm

• No fasting is usually required

• Best done in the morning for accurate results

Is the TSH test safe?

Yes. It is a simple, safe test with minimal risk.