
T4 Free & TSH-Ultrasensitive









The T4 Free & TSH-Ultrasensitive test measures the amount of free form of thyroxine (T4 Free or FT4) and thyroid stimulating hormone (TSH) in the blood. This test helps evaluate how well your thyroid gland works and detects possible thyroid disorders, including hyperthyroidism (too much thyroid hormones) and hypothyroidism (inadequate secretion of thyroid hormones).









Understanding T4 Free & TSH-Ultrasensitive
Thyroid-stimulating hormone (TSH), also known as thyrotropin, is produced by the pituitary gland present in the brain. TSH stimulates the thyroid gland to release thyroid hormones triiodothyronine (T3) and thyroxine (T4). Together, TSH, T3 & T4 hormones play a vital role in controlling how your body uses and stores energy and maintaining body weight and temperature.
T3 and T4 hormones exist in the blood in two forms: bound (attached to transport proteins) and free (not attached to proteins and can enter and affect the body tissues). The T4 Free & TSH-Ultrasensitive test measures the free form of T4 (FT4), a more accurate indicator of thyroid gland function than the bound form T4.
Your doctor may advise the T4 Free & TSH-Ultrasensitive test if you show symptoms suggestive of hyperthyroidism, such as increased appetite, weight loss, sweating, anxiety, tremors, etc., or hypothyroidism, such as fatigue, weight gain, dry skin, constipation, etc. This test is also recommended for women during pregnancy to check if they have adequate amounts of thyroid hormones, as these hormones are necessary for the healthy development of babies.
Abnormal levels of FT4 or TSH may indicate thyroid dysfunction (Hyperthyroidism or hypothyroidism), with high or low levels suggesting different types of thyroid disorders, such as goiter, Graves’ disease, or Hashimoto’s thyroiditis.
No special preparations are needed for this test. Usually, you do not need to stop taking your thyroid medication before taking this test. However, inform your doctor about all your medicines, as some can affect thyroid function.
Test result ranges are approximate and may differ slightly between labs depending on the methodology and laboratory guidelines. Talk to your doctor about your specific results. The test results will help them determine your medical condition, make recommendations for lifestyle modifications such as diet and exercise, evaluate whether or not medication will be required to manage your condition, and formulate an overall treatment plan.
What does T4 Free & TSH-Ultrasensitive measure?
Contains 2 testsThe T4 Free & TSH-Ultrasensitive test measures the free form of thyroxine (FT4) hormone along with TSH to analyze how well your thyroid gland is functioning. This test has the advantage of getting a more precise analysis of your thyroid function and early detection of potential thyroid problems, thereby facilitating better treatment outcomes.
The Thyroxine - Free (FT4) test measures the free form of thyroxine (T4) hormone made by the thyroid gland. T4 hormone exists in the blood in two forms: bound (attached to proteins) and free (not attached to proteins). Most of the T4 hormone circulating in the blood is bound to proteins and only a small part is free. A delicate balance of bound and free T4 should be maintained to ensure the proper functioning of the body.
Know more about Thyroxine - Free (FT4)
The TSH (Thyroid Stimulating Hormone) Ultrasensitive test measures the levels of TSH hormone in the blood. TSH is produced by the pituitary gland located at the base of the brain. Its function is to stimulate and regulate the functioning of the thyroid gland. It signals the thyroid gland to increase or decrease the production of thyroid hormones T3 and T4 when their levels are low or high, respectively. Therefore, when the levels of T3 & T4 decrease, the pituitary gland is stimulated to release TSH. This high TSH level, in turn, stimulates the thyroid gland to release more thyroid hormones (T3 & T4). It conversely happens when the levels of thyroid hormones increase.
Know more about TSH (Thyroid Stimulating Hormone) Ultrasensitive





FAQs related to T4 Free & TSH-Ultrasensitive
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- National Institute of Diabetes and Digestive and Kidney Diseases. Thyroid Tests [Internet]. National Institute of Health; May 2017 [Accessed 11 Jul. 2023]. Available from:
- Adhimoolam M, Arulmozhi R. Effect of antiepileptic drug therapy on thyroid hormones among adult epileptic patients: An analytical cross-sectional study. J Res Pharm Pract. 2016 Jul-Sep;5(3):171-4. doi: 10.4103/2279-042X.185717. [Accessed 11 Jul. 2023]. Available from:
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Other tests
- Thyroid Profile Total (T3, T4 & TSH)
- TSH (Thyroid Stimulating Hormone) Ultrasensitive
- Serum Calcium
- Thyroid Profile Free (FT3, FT4 & TSH)
- Anti-TPO Antibody (Anti-Thyroid Peroxidase Antibody)
- Thyroxine - Free (FT4)
- FT3 & FT4 (Free T3 & Free T4)
- PTH (Intact Parathyroid Hormone)
- T4 Free & TSH-Ultrasensitive,
- T3 & T4 Total
- CBC (Complete Blood Count)
- FBS (Fasting Blood Sugar)
- Thyroid Profile Total (T3, T4 & TSH)
- HbA1c (Glycosylated Hemoglobin)
- PPBS (Postprandial Blood Sugar)
- Lipid Profile
- Vitamin D (25-Hydroxy)
- Urine R/M (Urine Routine & Microscopy)
- Coronavirus Covid -19 test- RT PCR
- LFT (Liver Function Test)
- KFT (Kidney Function Test)
- TSH (Thyroid Stimulating Hormone) Ultrasensitive
- ESR (Erythrocyte Sedimentation Rate)
- Uric Acid, Serum
- Vitamin B12
- CRP (C-Reactive Protein), Quantitative
- Urine C/S (Urine Culture and Sensitivity)
- Serum Electrolytes
- Serum Calcium
- Serum Creatinine
- Diabetes Screening (HbA1C & Fasting Sugar)
- KFT with Electrolytes (Kidney Function Test with Electrolytes)
- Cholesterol - Total
- Hb (Hemoglobin)
- Complete Hemogram (CBC & ESR)

















