✍️ Edited by Farhan Ahmed, Editor, MedTestBD · Last updated: July 2026
What is TSH?
TSH (Thyroid Stimulating Hormone) is a hormone produced by the pituitary gland — a small gland at the base of the brain. Its job is to signal the thyroid gland to produce thyroid hormones (T3 and T4), which control the body's metabolism, energy levels, heart rate, body temperature, and many other vital functions.
When thyroid hormone levels in the blood are low, the pituitary releases more TSH to stimulate the thyroid. When levels are high, TSH drops. This feedback system makes TSH the single most sensitive indicator of thyroid function — even small changes in thyroid health show up in TSH levels before symptoms appear.
Why is the TSH Test Done?
- Screen for thyroid disorders — TSH is always the first test ordered when thyroid disease is suspected.
- Diagnose Hypothyroidism — an underactive thyroid. High TSH means the pituitary is working harder to stimulate a sluggish thyroid.
- Diagnose Hyperthyroidism — an overactive thyroid. Low TSH means the thyroid is already producing too much hormone on its own.
- Monitor thyroid treatment — patients on levothyroxine (thyroxine) tablets need regular TSH checks to ensure the dose is correct.
- Evaluate fertility problems — abnormal TSH can interfere with ovulation and menstrual cycles.
- Pregnancy screening — thyroid disorders are common during pregnancy and can affect fetal brain development if untreated.
TSH Normal Range
The standard TSH reference range for adults is 0.4 – 4.0 mIU/L, though some laboratories use slightly different ranges. Interpretation depends on context:
- TSH above 4.0 mIU/L — suggests hypothyroidism (underactive thyroid). The higher the TSH, the more severe the deficiency.
- TSH below 0.4 mIU/L — suggests hyperthyroidism (overactive thyroid).
- Pregnancy: TSH targets are lower — ideally below 2.5 mIU/L in the first trimester.
- Elderly patients may naturally have slightly higher TSH without disease.
A single abnormal TSH result should always be confirmed with a repeat test and, if needed, Free T4 and Free T3 measurements before starting any treatment.
TSH Alone vs. Full Thyroid Panel
TSH is the best starting point, but it does not tell the whole story. If TSH is abnormal, your doctor will likely order:
- Free T3 — the active form of thyroid hormone at the cellular level.
- Free T4 — the main hormone released by the thyroid gland.
- Anti-Thyroid Antibodies — to check for autoimmune thyroid disease (Hashimoto's or Graves' disease).
How to Prepare for the TSH Test
- No fasting is required for a TSH test.
- The test can be done at any time of day, though many doctors prefer morning samples as TSH is slightly higher in the early hours.
- If you are already on thyroid medication (levothyroxine), take the blood sample before your morning dose for the most accurate result — unless your doctor advises otherwise.
- Inform your doctor about biotin supplements, as high-dose biotin can falsely affect TSH results.
TSH Test Price in Bangladesh
TSH test prices vary significantly across diagnostic centers in Bangladesh — from government hospitals offering it at very affordable rates to private centers charging considerably more. Use MedTestBD to compare current TSH test prices from labs near you and choose the most cost-effective option without compromising on quality.
Normal ranges cited on this page are based on MedlinePlus and WHO guidance. Prices are collected from public sources and may change — confirm with the facility before visiting. This information is for general reference only and is not medical advice. Always consult a qualified physician.
