What It Measures#
The TSH (Thyroid Stimulating Hormone) test measures the level of TSH in your blood. TSH is produced by the pituitary gland (in the brain) and acts as the master controller of your thyroid gland. It works through a feedback loop:
- When thyroid hormones (T3, T4) are low, the pituitary releases more TSH to stimulate the thyroid — resulting in a high TSH (hypothyroidism).
- When thyroid hormones are high, the pituitary reduces TSH — resulting in a low TSH (hyperthyroidism).
TSH is the single most sensitive test for detecting thyroid dysfunction. It catches abnormalities earlier than T3 or T4, even in subclinical stages when the patient may have no symptoms.
For a comprehensive thyroid evaluation including T3 and T4, see Thyroid Function Test.
Who Should Get Tested#
- Women above 30 — especially with fatigue, weight changes, or menstrual irregularity.
- Anyone with a family history of thyroid disease.
- Pregnant women — in the first trimester and as advised by their obstetrician.
- People with symptoms: cold intolerance, constipation, dry skin, hair loss (hypothyroid); or heat intolerance, tremors, rapid heartbeat, weight loss (hyperthyroid).
- Patients with PCOD/PCOS or infertility.
- Infants — neonatal TSH screening is standard in many Indian states.
- Anyone on thyroid medication — for dose monitoring.
How to Prepare#
- No fasting required.
- Test in the early morning (before 10 AM) for the most accurate result, as TSH peaks in the early hours and drops by 50% by afternoon.
- If on thyroid medication (levothyroxine), collect the sample before taking your morning dose.
- Inform your doctor about biotin supplements — they can interfere with TSH assays.
Understanding Your Results#
| TSH Level (mIU/L) | Interpretation | |-------------------|---------------| | 0.4–4.0 | Normal (euthyroid) | | 4.0–10.0 | Subclinical hypothyroidism — may not need treatment; monitor | | Above 10.0 | Overt hypothyroidism — treatment usually recommended | | Below 0.4 | Low TSH — suggests hyperthyroidism; needs Free T3, T4 confirmation | | Below 0.1 | Suppressed TSH — likely overt hyperthyroidism |
In pregnancy, TSH targets are stricter: first trimester < 2.5 mIU/L, second/third trimester < 3.0 mIU/L. Uncontrolled thyroid in pregnancy can affect foetal neurodevelopment.
Related Tests#
- Thyroid Function Test (T3, T4) — full panel when TSH is abnormal.
- Vitamin D Test — commonly deficient alongside thyroid disorders.
- Lipid Profile — hypothyroidism raises cholesterol.
- CBC — anaemia is a common comorbidity.
Booking & Home Collection#
Book a TSH test on PingMeDoc — early-morning slots for optimal accuracy. Home collection available. Reports within 12–24 hours.