What does a TSH lab test measure ? A TSH lab test measures the level of thyroid stimulating hormone in the blood. Thyroid stimulating hormone is released by the pituitary gland and its function is to regulate the release of thyroid hormones from the thyroid gland. FAQs : Are there any risks associated with this test ? There are no known risks associated with this test. Can this test be performed in children ? This test can be performed in children if necessary. How should I prepare for this test? No special preparation is needed for this test. What does a high TSH test result indicate? A high TSH test result indicates that you have an underactive thyroid gland. What are the causes behind a high TSH level? Any infection or inflammation affecting the thyroid gland such as Hashimoto’s thyroiditis or autoimmune thyroiditis will cause the TSH level to be raised.