The Thyroglobulin test measures the level of thyroglobulin, a protein produced by the thyroid gland, in the blood. It is primarily used as a tumor marker in individuals who have had thyroid cancer to monitor for recurrence after treatment. Elevated thyroglobulin levels may indicate remaining thyroid tissue or cancerous cells post-thyroidectomy. It can also aid in diagnosing thyroid disorders like hyperthyroidism and thyroiditis. This test is typically used alongside imaging and other thyroid function tests for a thorough evaluation.