A thyroid profile test is a diagnostic tool used to assess the health of the thyroid gland. The test measures the levels of three hormones produced by the gland: triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH). TSH is a hormone produced by the pituitary gland, which stimulates the thyroid gland to produce T3 and T4. Abnormal levels of T3, T4, and TSH can indicate an underactive or overactive thyroid gland, which can cause a variety of symptoms such as weight changes, fatigue, hair loss, and mood changes. The thyroid profile test is a simple blood test and is usually ordered by a healthcare provider to evaluate thyroid function and to help diagnose thyroid disorders.