Your thyroid gland is essential to the normal functioning of the body’s processes. Too little thyroid hormone and your body becomes ‘slow’ and often leads to ill health, weight gain, feeling tired. Too much thyroid hormone can lead to palpitations, excessive weight loss, anxiety, increased bowel movements. To get the right balance in your thyroid hormone production is very important and this test looks out for: Free T4 (Thyroxine) and Thyroid Stimulating Hormone (TSH) to determine how well your thyroid gland is functioning.