What is this test?
TSH is the hormone released by the pituitary gland in the brain that stimulates the thyroid gland. It is the first-line test for assessing thyroid function: a high TSH usually suggests an underactive thyroid (hypothyroidism), while a low TSH suggests an overactive thyroid (hyperthyroidism). It is also used to monitor dosing in patients on thyroid medication.
When is it requested?
Investigation of thyroid diseases and treatment monitoring
What does a high TSH result mean?
A high TSH means the pituitary is pushing the thyroid to work harder and most often suggests an underactive thyroid (hypothyroidism). Mild rises can be temporary.
- Thyroid medication dose too low or taken irregularly
- Hashimoto's thyroiditis (the most common cause)
- Recovery phase after a serious illness (temporary rise)
- After thyroid surgery or radioactive iodine treatment
- Certain medicines (e.g., lithium, amiodarone) and too much or too little iodine
- Blood drawn early in the morning (TSH is higher at night and early morning)
- Very rarely, pituitary causes
What does a low TSH result mean?
A low TSH most often suggests an overactive thyroid (hyperthyroidism) or too high a thyroid medication dose; it can also be normally low in early pregnancy.
- Thyroid medication dose higher than needed
- First trimester of pregnancy (effect of the pregnancy hormone)
- High-dose biotin supplements (falsely low result)
- Some medicines such as corticosteroids, or a period of severe illness
- Graves' disease or an overactive thyroid nodule
- Early phase of thyroid inflammation (thyroiditis)
- Rarely, an underactive pituitary gland
My result is outside the reference range. What should I do?
TSH is interpreted with free T4; one result alone is not a diagnosis, and borderline values may be rechecked in a few weeks. Stop biotin at least 2 days before the test and tell your doctor about your medicines.
Reference ranges depend on the method, age and sex; always use the range printed on your report. This information is for general guidance only; consult your doctor for diagnosis and treatment.
Sample information
- Sample type: Serum
- Tube / container: Red / yellow-top tube
- Sample volume: 1 mL
Preparation
Fasting sample recommended.
Testing and results
- Method: ECLI
- Run schedule: Daily
- Turnaround time: 4 hours
Price and appointment
Add the test to your list to receive a price quote by e-mail, or call +90 850 640 07 30 / message us on WhatsApp (+90 537 301 22 14). You can have the test done at our branches or with our home blood collection service. Results can be viewed online with your Turkish ID number (or passport number for foreign nationals).