Mayo Clinic Minute: How the thyroid affects the heart

The thyroid is a small butterfly-shaped gland in the front of the neck. It produces a hormone called thyroxine or T4 that controls virtually every organ system in the body.

Dr. Robert Smallridge says when thyroid levels are unbalanced, if can affect cardiovascular functions.

Hyperthyroidism, on the other hand, can increase the risk of atrial fibrillation.