Thyroid Panel (blood test)-Abnormal thyroid hormone levels are a common cause of anxiety, depression, forgetfulness, confusion, and lethargy. Having low thyroid levels decreases overall brain activity, which can impair your thinking, judgment, and self-control and make it very hard for you to feel good. Low thyroid functioning can make it nearly impossible to manage weight effectively. To know your thyroid levels, you need to know these figures: thyroid-stimulating hormone (TSH) Free T3 Free T4 Thyroid antibodies (thyroid peroxidase and thyroglobulin antibodies)