Thyroid capacity tests are a progression of blood tests used to gauge how well your thyroid organ is functioning. Accessible tests incorporate the T3, T3RU, T4, and TSH. Medical services experts utilize thyroid tests to check how well your thyroid is functioning and to find the reason for issues like hyperthyroidism or hypothyroidism. The thyroid is a little, butterfly-formed organ toward the front of your neck that makes two thyroid chemicals: thyroxine (T4) and triiodothyronine (T3). Thyroid chemicals control how the body utilizes energy, so they influence virtually every organ in your body, even your heart.