Hypothyroidism (hye-poe-THYE-royd-izum) is when the thyroid gland doesn't send enough thyroid hormone into the blood. 

More to Know

The thyroid is a gland in the front of the neck. It makes hormones that help with many body functions. When the amount of thyroid hormone is below normal, the body uses energy more slowly. Chemical activity (metabolism) in the cells slows down.

People with mild hypothyroidism may feel just fine, but if the problem gets worse they can start to feel sluggish and weak. Hypothyroidism can hold back growth and puberty in kids and teens. People with the condition may notice dry skin, hair loss, constipation, and feeling colder than others. They can also have trouble concentrating and forget things easily. 

Keep in Mind

Doctors can prescribe thyroid hormone replacement pills to bring the body's levels of thyroid hormone back to normal. 

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.