Weight Gain or Loss and Other Signs of Thyroid Issues

Elizabeth Millard
by Elizabeth Millard
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Weight Gain or Loss and Other Signs of Thyroid Issues

People gain weight for a number of reasons that go beyond the standard calorie-surplus equation tied to eating more than you burn. You might have switched to a new medication, for example, and one of the side effects could be bloating or excess weight. Or your crushing work deadlines and stress overload could play a factor, causing weight changes even though your macros remain exactly the same.

But if you’ve eliminated possibilities like these and still struggle, it might be time to check with your doctor for one additional factor: your thyroid.

According to the American Thyroid Association, more than 12% of the U.S. population will develop a thyroid condition during their lifetime, and up to 60% of those people will be unaware of the problem. Women are 5–8 times more likely than men to have thyroid problems, but the issue can affect anyone.


A quick primer: Your thyroid gland is located in the middle of the lower part of your neck, and looks a bit like a butterfly.

Although it’s small, it produces a hormone called thyroxine that affects every cell, tissue and organ in the body — staying on top of jobs like helping the body use energy, regulating temperature and streamlining operation in the brain, heart and muscles.

That’s why, when it’s off, you may have symptoms that take time to recognize as being related to thyroid function. Let’s take a look at the two main problems that can happen, along with the symptoms to keep in mind:


Also known as “low thyroid” or “underactive thyroid,” this condition happens when the thyroid gland doesn’t produce enough thyroid hormone, an issue that can affect your metabolism.

That can cause weight gain — and unfortunately, much of that is stored as fat — but it’s often not the only sign something could be out of whack. Many people with this issue also experience:

  • Fatigue: Your thyroid hormone controls your energy balance, so you may feel a low-level exhaustion and reduced motivation to stay active. Plus, even though you may try to sleep more to make up for it, your low-thyroid problem may cause you to still feel unrested.
  • Constantly feeling cold: With hypothyroidism, you’ll see a reduction in your basal metabolic rate — the number of calories required to keep your body functioning at rest — and that reduces the amount of heat your body generates. If you’re always reaching for a sweater while other people are in T-shirts, it could mean your thyroid is off.
  • Weakness: When thyroid hormone production is low, it heightens a process called catabolism, when the body uses tissue like muscles to create more energy. You’d likely feel weakness in the muscles because of this, as well as aching, muscle cramps, or soreness — as if you’ve had a hard workout, even when you haven’t.

Other signs of hypothyroidism include hair loss, mood changes, dry skin, difficulty concentrating, or digestive problems like constipation.


When your thyroid gland swings in the other direction and is producing too much thyroxine, you can also have weight issues, but on the opposite end of the spectrum. People with this condition often experience unintentional weight loss, even when they attempt to add calories to make up for it. Other signs include:

  • Infertility: If you’ve been struggling to get pregnant, it’s possible even mild thyroid dysfunction could be a factor, according to a study women with unexplained infertility were nearly twice as likely to have higher levels of thyroid-stimulating hormones.
  • Bulging eyes: The most common form of hyperthyroidism is called Graves’ Disease, and one hallmark symptom is elevation of the upper eyelids — which causes eyes to take on a bulging appearance.
  • Rapid heartbeat: The thyroid has a strong effect on the heart’s function, so overactivity in the thyroid can lead to a similar issue in the heart. That might lead to mild symptoms like a faster resting heart rate, but it could also be more serious, like causing atrial fibrillation.

Much like hypothyroidism, you may also experience issues with your skin and hair, fatigue, difficulty sleeping, mood changes and problems concentrating. Irritability, nervousness and anxiety are more common with hyperthyroidism, while depression and a sense of joylessness are seen more often with hypothyroidism.


Whether you have just a couple of these symptoms or maybe just one, like struggles with weight gain, it’s worth getting your thyroid levels checked. Sometimes, thyroid problems can lead to more serious issues like thyroid cancer, brittle bones, vision loss or autoimmune difficulties.

About the Author

Elizabeth Millard
Elizabeth Millard

Elizabeth is a freelance journalist specializing in health and fitness, as well as an ACE certified personal trainer and Yoga Alliance registered yoga teacher. Her work has appeared in SELF, Runner’s World, Women’s Health and CNN.


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