FT4 & TSH (ULTRASENSITIVE), SERUM

FT4 & TSH (Ultrasensitive), Serum

What it is

The FT4 & TSH (Ultrasensitive), Serum test is a combined thyroid profile that measures Free Thyroxine (FT4) and Thyroid Stimulating Hormone (TSH) levels in the blood. FT4 is the active thyroid hormone that regulates metabolism, growth, and energy balance, while TSH is produced by the pituitary gland to control thyroid activity. The ultrasensitive TSH assay provides highly accurate detection of even very small changes in thyroid function.

Uses

This combined test is widely used for:

• Diagnosing hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid).
• Monitoring thyroid disorders, including Hashimoto’s thyroiditis and Graves’ disease.
• Evaluating treatment response in patients on thyroid hormone replacement or anti-thyroid therapy.
• Screening for thyroid dysfunction in pregnancy or high-risk individuals.
• Assessing pituitary gland function related to thyroid hormone regulation.

Symptoms That May Lead to the Test

Your doctor may recommend this test if you experience signs of thyroid imbalance such as fatigue, unexplained weight gain or loss, hair thinning, depression, constipation, heat or cold intolerance, irregular heartbeat, sweating, or swelling in the neck (goiter).

Abnormal Results

High TSH with Low FT4: Indicates primary hypothyroidism, commonly due to Hashimoto’s thyroiditis or iodine deficiency.

Low TSH with High FT4: Suggests hyperthyroidism, often caused by Graves’ disease, thyroid nodules, or thyroiditis.

Low TSH with Low FT4: May indicate pituitary or hypothalamic dysfunction (secondary hypothyroidism).

Normal TSH with Abnormal FT4: May suggest subclinical thyroid disease or medication-related changes.

Risks

The test requires a standard blood sample. Risks are minimal and may include slight pain, bruising, or dizziness at the puncture site. These are temporary and uncommon.