Cytomel is a brand and trade name for T3, which is Liothyronine Sodium. Liothyronine Sodium is a synthetic variant of the human body’s own thyroid hormone. It should be understood that the human body’s own natural endogenously manufactured thyroid hormone is actually known as Triiodothyronine, which is different from Liothyronine Sodium. Liothyronine is the L-isomer of Triiodothyronine. Liothyronine and Triiodothyronine are both nearly identical with one another, but Liothyronine is a more potent variant and is also better absorbed orally, which is why it has been developed into a prescription medicine and preparation known as Cytomel, Tiromel, Tertroxin, etc. Within a medical and clinical setting, Cytomel (T3) is utilized in the treatment of hypothyroidism, which is a condition whereby an individual’s thyroid gland is not secreting the proper and normal levels of thyroid hormone for proper function.