The TSH (Thyroid Stimulating Hormone) test is a key blood test used to assess how well the thyroid gland is functioning. TSH is produced by the pituitary gland and regulates the production of thyroid hormones (T3 and T4), which control metabolism, energy levels, and overall body functions.

This test is commonly used as the first-line investigation to detect thyroid disorders, including hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid).

The test measures the amount of TSH in the blood. When thyroid hormone levels are low, the pituitary gland releases more TSH to stimulate the thyroid. Conversely, when thyroid hormone levels are high, TSH levels decrease. This balance helps determine thyroid health.