Shaped like a butterfly or bow tie and sitting at the front of your neck, the thyroid gland is the master of your metabolism.

Weighing in at less than one ounce, the thyroid may be small, but it plays a big role in regulating how your body uses and stores energy from the foods you eat. Because the thyroid gland releases hormones that affect most of the body’s organs, production of too much or two little hormone could harm your health.

“Your thyroid gland releases two hormones that enter your bloodstream and control how your body uses and stores energy. Problems with your thyroid disrupt this metabolic function, through either an overproduction or underproduction of these hormones, which has widespread consequences throughout the body,” explains Bryan R. Haugen, MD from The Hormone Foundation, a leading educational resource for hormone-related health issues. “It’s serious because thyroid problems affect a large number of people, and most people don’t even know what their thyroid does.”

The Journal of Medical Sciences estimates at least 300 million people worldwide have a thyroid dysfunction, yet nearly half are presumed unaware of their condition. Despite this lack of awareness, thyroid problems are front and center in mainstream culture. Celebrities from Oprah to fitness guru Jillian Michaels suffer from an underactive thyroid, a specific condition called hypothyroidism, the most common thyroid disorder.

Hypothyroidism occurs when the body lacks sufficient thyroid hormone, and the symptoms of hypothyroidism usually appear slowly over months or years. Common symptoms of hypothyroidism include fatigue, weakness, weight gain or increased difficulty losing weight, hair loss, cold intolerance, muscle cramps, constipation and depression. Because early symptoms can be mild or mistakenly associated with other conditions (such as depression, especially during and after pregnancy, stress, and aging) it is possible that a hypothyroidism diagnosis can be missed or delayed. Although it helps to know what to look for, patients don’t have to exhibit all of the symptoms to be diagnosed with this condition.

Some people are more likely than others to develop thyroid problems (it occurs more often in women and people over age 60, and tends to run in families). Although you can’t prevent thyroid disease, it’s important to detect it early. Untreated hypothyroidism can cause severe complications, so people who have a family history of thyroid disease or other risk factors should talk with their doctor about about regular screenings to ensure a prompt diagnosis.