World Thyroid Day is May 25, 2009, a day to promote awareness and understanding of thyroid health and the advances made in treating thyroid diseases.

Diseases of the thyroid are very common and affect tens of millions of people worldwide.

The thyroid, a butterfly-shaped gland located in the neck, produces hormones that influence virtually every cell, tissue and organ in the body.

The thyroid regulates the body's metabolism--the rate at which the body produces energy from nutrients and oxygen--and affects critical body functions, such as energy level and heart rate.