You might not know much about your thyroid, but the tiny, butterfly-shaped gland is one serious under-the-radar powerhouse. In fact, the thyroid produces a hormone that influences every cell, tissue and organ in the body, according to the American Thyroid Association (ATA). “Thyroid hormone makes everything work better,” says Bryan Haugen, M.D., an endocrinologist and the past president of the ATA. “It makes your heart beat stronger and your metabolism go faster. It regulates your temperature and your gut, as far as absorption. It even makes your brain work better.”

ALWAYS COLD?

“If you’re often finding yourself in a scenario where everyone in the room feels fine, and yet you’re clamoring for a sweater, an underactive thyroid may be to blame.”

But in some people, the immune system decides to attack the thyroid, mistakenly pegging it as a foreign entity. This can lead to hypothyroidism, in which the thyroid gland doesn’t produce enough thyroid hormone, causing everything from your ability to burn calories to being able to think clearly to slow down.Wondering if your thyroid is down for the count? Check out 7 common signs of hypothyroidism:

1. You’ve put on five or more pounds and can’t figure out why. With hypothyroidism, “it’s like the thermostat in your house has been turned down,” notes Dr. Haugen. Except in this case, the thermostat is your metabolism and the house is your body. The result? You’re burning calories at a slower rate and have gained weight—5-20 pounds is typical—even though your eating and exercise habits haven’t changed. Plus, you have difficulty dropping those extra pounds.

2. Your skin has become dry and flakey. Normal, healthy skin naturally sloughs off dead skin cells. But that process slows down with hypothyroidism, so you start to get more flakey, dry skin. (Try these tips to soothe and hydrate dry skin.)

3. You’re always cold. It’s that same thermostat effect again. People with hypothyroidism tend to feel cold and sweat less. So if you’re often finding yourself in a scenario where everyone in the room feels fine, and yet you’re clamoring for a sweater, an underactive thyroid may be to blame.

MENTAL FOG?

“Everything, including your brain, is more sluggish when your thyroid is underperforming.”

4. You’re walking around in a bit of a mental fog. Everything, including your brain, is more sluggish when your thyroid is underperforming, making it harder to remember things and to think as clearly as you used to.

5. Your energy conks out faster than usual during your workouts. “When you don’t have enough thyroid hormone, the heart rate can slow down and you can’t exercise as well,” says Haugen.

6. You’re constipated. With hypothyroidism, “the colon moves more slowly and more water is absorbed, so people get constipated,” notes Haugen.

7. Your other health issues are getting worse. An underactive thyroid can aggravate current health issues such as depression.

Low Energy?

If you feel like you don’t have enough energy, ask your doc to examine your thyroid gland with the following tests. Your history is a big part of your diagnosis, but these tests can aid your doctor.

MORE: Tests for an Abnormal Thyroid

infertility and abnormal menstrual cycles. For example, an underactive thyroid can make mild depression worse, or for women who were borderline when it came to producing enough viable eggs for fertilization, hypothyroidism can make getting pregnant more challenging, notes Haugen.Got one or more of the symptoms above? It’s worth mentioning it to your primary care physician and having a blood test. If you’re diagnosed with hypothyroidism, you’ll likely be put on life-long prescription medication to supplement the thyroid hormone and get your body back in balance.

MORE: Tips to Boost Your Energy Level