The thyroid gland is responsible for regulating how your body uses energy. The thyroid also produces hormones critical to proper cell and system functioning. The Thyroid Panel screens for thyroid disease, hyperthyroidism and hypothyroidism by examining your body’s production of the thyroid hormones TSH, T3 and T4. This panel also includes your Thyroxine Index – basically a math computation estimate based on your T4 and T3 tests. There are two types of thyroid disorders including: • Hypothyroidism (underactive thyroid) – symptoms may include fatigue, weight gain, a short attention span, and numbness or cold intolerance. • Hyperthyroidism (overactive thyroid) – symptoms may include weight loss, persistent vomiting, increased blood pressure, hair loss or a persistently fast heart rate.