Children can be at risk for hypothyroidism

About 5 percent of the 27 million American thyroid disorder sufferers are children. The number includes an estimated 13 million who are undiagnosed, according to the American Association of Clinical Endocrinologists, reports. This means that while thyroid disorders in children are not common, they are also not rare.

"Thyroxine is a very, very important hormone," Dr Vijaya Prasad, a pediatric endocrinologist at St. Joseph's Hospital for children told the news source. "In the fetus and young child, it affects central nervous system development. Without the thyroid hormone, the brain is not going to develop normally."

Hypothyroidism often starts slowly during childhood, when the brain is mostly developed. This acquired hypothyroidism can take a long time - even years - before the effects are noticed.

The condition is much more common in children than hyperthyroidism, which affects only about .04 percent of children, mostly teenage girls.

"The most common symptom is growth failure," notes Prasad. "Many people think that when a child has this they become heavier and heavier. But that's not true. Hypothyroidism doesn't cause obesity. It stops them from growing."