Having trouble losing weight and can’t pinpoint why? Your thyroid (the butterfly-shaped gland in the front of your neck) could be the culprit. Thyroid hormones are in charge of how your body uses energy. When you don’t have enough of these hormones, many of your body’s functions, including your metabolism, slow down.

But because some symptoms surrounding thyroid disorders (things like fatigue and cold intolerance) can be vague and associated with other medical conditions, it takes some people a while before they zero in on their thyroid as the reason for their weight fluctuations, explains Dr. Carrie Lam, M.D.

To help shed light on this essential hormone-producing gland, January is National Thyroid Awareness Month. According to the American Thyroid Association, one in 10 people suffer from a thyroid disorder. Hypothyroidism (which causes weight gain) occurs in five out of 100 Americans over the age of 12, according to the National Institutes of Health. Meanwhile, hyperthyroidism, which can cause weight loss, affects about one in 100 Americans over the age of 12.

“Thyroid health is more important than many people understand, especially when you factor in the number of people impacted by thyroid disorders,” says Dr. Jeffrey Dlott, M.D., Medical Director, QuestDirect, a lab test company.

Here’s what else you need to know about how your thyroid affects weight loss and overall wellness.

How Your Thyroid Affects Weight Loss

The thyroid is a hormone-producing gland that regulates the body’s metabolism, which is the rate at which the body produces energy from nutrients and oxygen, explains Dott. It impacts key body functions, such as energy level and heart rate.

“While the thyroid gland is relatively small, the hormone it produces influences every cell, tissue, and organ in the body,” he says. For those with hyperthyroidism—when the thyroid gland produces excess levels of the thyroid hormone, thyroxine—your metabolism can increase, causing weight loss and an irregular heartbeat, Dott says. The condition is also known as overactive thyroid disease. Graves disease is a form of hyperthyroidism.

“On the flip side, hypothyroidism occurs when you have an under-active thyroid, meaning the thyroid gland doesn’t produce enough thyroid-stimulating hormone (TSH),” Dott says. This deficiency can disrupt things such as heart rate, body temperature, and all aspects of metabolism, resulting in weight gain.

A common problem for those with undiagnosed hypothyroidism is that they may start dieting or restricting food. This can then lead to even further weight gain. That’s because an underactive thyroid gland will cause your body to conserve even more calories than before, Lam says.

Read More: Here’s Why Your Workout Might Be Causing Weight Gain

Signs Of Hypothyroidism and When to See a Doctor

Beyond changes in your weight, other symptoms of low thyroid include feeling fatigued, cold intolerance, constipation, and dry skin and hair, says Leann Poston, M.D., a consulting physician with Impakt Fitness. Joint and muscle pain, heavy or irregular menstrual periods or fertility problems, and depression may also be some signs.

If you have these symptoms, Poston suggests contacting your doctor to be tested for thyroid dysfunction. A blood test checking your Thyroid-Stimulating Hormone (TSH) levels as well as your thyroxine (T4), a hormone produced by your thyroid, can provide insight into whether you have a thyroid disorder, she says.

Hypothyroidism is more common among people who are 60 and older, according to the NIH. Those who have had a thyroid problem in the past, such as a goiter, may be at higher risk for hypothyroidism. Ditto for those who have had radiation treatment to the thyroid, neck, or chest, or have a family history of thyroid disease may also be at a higher risk of hypothyroidism.

Also, Lam says, iodine deficiency is often linked to a lack of thyroid hormone production. Dietary supplements may replace or raise levels of iodine, he says. Still, it’s good to consult with a doctor to best understand the root cause of any thyroid hormone imbalances.

Michael’s Thyroid Factors is a nutritional supplement that contains iodine as well as manganese and tyrosine. As always, talk with a doctor or registered dietitian before adding a new vitamin or supplement to your routine.

Read More: 5 Signs You Need To Eat More Carbs

Losing Weight If You Have Hypothyroidism

If your test results show that your thyroid isn’t producing enough hormones, work with experts to create a tailored plan.

Depending on the condition, possible treatment options may include anti-thyroid medications, beta blockers, surgery (i.e., thyroidectomy), or radioactive iodine. For the latter, this is taken orally, and the thyroid gland absorbs the radioactive iodine, shrinking it, Dott says.

For those with hypothyroidism, a common misconception is that they’ll never be able to lose weight, Dott says. However, with the proper dosage of medicine, patients can manage their thyroid health without affecting their ability to lose weight. Plus, with increased energy, patients could potentially find it easier to work out as well, he says.