Whether you’ve had trouble pooping, can’t stop yawning all day long, feel constantly hot or chilly, or can’t sit still, these seemingly random symptoms may point to an issue with one teeny tiny body part: your thyroid.

According to the American Thyroid Association, up to 20 million Americans have some form of thyroid disease—and a whopping 60 percent of them don’t even know it. Yikes. We blame everything from weight gain to wonky energy levels on our thyroid levels—but how much do you know about this small but powerful gland?

What Exactly Is Your Thyroid?

The thyroid is a butterfly-shaped gland located in your neck that produces hormones which  help your entire body work efficiently, says Supneet Saluja, M.D., an endocrinology specialist at Mercy Medical Center in Baltimore.

We often associate the thyroid with one thing in particular: metabolism. “The thyroid is the master of metabolism,” says John Robinson, a board-certified naturopathic medical doctor and founder of The Hormone Zone in Scottsdale, Arizona. And by metabolism, we’re not just talking about your body’s ability to lose fat and keep up your energy levels. On a cellular level, metabolism is a set of chemical reactions that allows cells in just about every part of your body (think your brain, heart, nervous system, and liver) to do their jobs.

Related: 5 Myths About Your Metabolism—Busted

Problem is, the thyroid doesn’t always work the way it should.

What Happens When Your Thyroid Isn’t On Its A-Game?

The most common thyroid issue involves the gland not producing enough thyroid hormone to keep your body running on all cylinders— and this is called hypothyroidism, says Robinson.

If you have an underactive thyroid gland, you may experience symptoms like unexplained weight gain, hair loss, constipation, fatigue, dry skin, and/or depression—without any change in your activity or diet, says Saluja. (Women with underactive thyroids may also experience heavier periods, Robinson adds.)

Related: 8 Possible Reasons Why You’re So Tired All The Time

An overactive thyroid, called hyperthyroidism, is a lot less common. If you have an overactive thyroid gland, you may experience an unusually fast heartbeat, anxiety, trouble sleeping, and/or diarrhea, says Saluja. Because it can affect the heart, hyperthyroidism is potentially much more dangerous than hypothyroidism if untreated, says Robinson.

Another note for the ladies: According to the American Thyroid Association, women are a whopping five to eight times more likely to deal with thyroid problems—although experts don’t know for certain why that is.

But what the heck throws off the thyroid in the first place? A lot of times, an underlying autoimmune disease is to blame, says Saluja. In the case of an underactive thyroid gland, the culprit may be Hashimoto’s Thyroiditis, an autoimmune disease in which your immune system attacks your thyroid. When it comes to an overactive thyroid gland, the culprit may be Graves’ disease, an autoimmune condition in which the body produces too much of an antibody that spurs thyroid hormone production.

According to the National Institutes of Health, no one’s really sure what, exactly, causes autoimmune diseases in general. Saluja notes, though, that thyroid disorders often run in the family, so if you’re experiencing any signs of a whacked out thyroid and have a loved one who’s also had issues, talk to your doctor about testing your TSH (thyroid stimulating hormone) levels.

What Can You Do About An Off-Kilter Thyroid?

First things first, if you suspect something is off with your thyroid, you’ll need a blood test to confirm whether your hormone levels are too high or too low, says Saluja.

If you’re diagnosed with underactive thyroid (hypothyroidism), the treatment is, luckily, pretty simple: Your doc will likely prescribe hormone for you to take. “This shouldn’t be considered medication,” says Saluja. “It’s really your own body’s hormone that is available in pill form.”

Treating an overactive thyroid gland (hyperthyroidism) can be a little trickier, though, because you’re actively trying to manipulate hormone production, says Saluja. Your doc may prescribe radioactive iodine—which can be taken in pill or liquid form—to destroy thyroid tissue and decrease how much hormone it produces.

While this can cure hyperthyroidism, it can actually leave you with the opposite problem—low thyroid—afterwards, says Saluja. No need to panic, though. Like Saluja said, it’s much easier to treat hypothyroidism than hyperthyroidism.