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20 Signs of an Underactive Thyroid

9 min read

By Katherine George

Medically Reviewed by Dr. Gerald Morris

According to the American Thyroid Association (ATA), roughly 5-percent of U.S. adults suffer from hypothyroidism, or an underactive thyroid, making it the most prevalent immune disease in North America. An underactive thyroid results when the body doesn’t produce adequate thyroid hormone, thus affecting both normal brain, mood, and body function. Sadly the National Academy of Hypothyroidism, reports that 60-percent of those with thyroid disease don’t realize that they have a health issue due to a presentation of very commonplace symptoms, such as weight gain, moodiness, extreme fatigue, and digestive upset.

The following 20 symptoms could indicate an underactive thyroid, but it’s important to remember that symptoms occur on an individual basis. Each person will experience a different number of these symptoms and to varying degrees. Let’s take a look at what these symptoms are…

1. Unexplained Fatigue

Unexplained fatigue is one of the most common side effects of hypothyroidism. This is because the thyroid hormone controls energy levels and is responsible for letting the body know when it needs a nap. A perfect example (which is also on the extreme end) is when animals go into hibernation, they’ll experience low thyroid levels leading up to their seasonal nap. If you get an adequate amount of sleep (roughly 8 hours per night) and still struggle to get up in the morning, you may suffer from hypothyroidism. Many diagnosed patients report dealing with unexplained and severe forms of exhaustion throughout the day, even after a night of restful sleep.

“Thyroid hormone receives signals from the brain and coordinates cells to change their functions, depending on what else is going on in your body,” says Healthline. “Those with high levels of thyroid hormone feel nervous and jittery. In contrast, people with low levels of thyroid hormone feel exhausted and sluggish.”

2. Digestive Upset

If you suffer from chronic indigestion almost every single time you eat, it could indicate an underactive thyroid. The condition may even cause you to suffer gas, bloating, and abdominal cramps with foods that you’ve eaten for years without any issues. (Check out the article “Hypothyroidism Diet: 6 Foods to Eat and 6 Foods to Avoid” to find out more about what to eat).

3. Irritability

Individuals who have an underactive thyroid share common mood imbalances. For instance, a co-study conducted by researchers at the University of Toronto and the Department of Psychiatry at Toronto’s Western Hospital linked hypothyroidism to dangerous and permanent effects on brain function and mental processes—including a gradual loss of interest and motivation, paranoia, irritability and poor short-term memory.

4. Baffling Weight Gain

Unexpected weight gain is another very common side effect of hypothyroidism. This is best noticed when a person’s diet hasn’t changed at all and their activity level is the same as it always was, but they continue to gain weight without any practical reason behind it. The same goes for trying to shed said unexplained weight. If you increase your activity level, cut calories and still don’t shed a pound, hypothyroidism may explain it.

“When thyroid levels are low, metabolism switches modes. Instead of burning calories for growth and activity, the amount of energy you use at rest, or your basal metabolic rate, decreases. As a result, your body tends to store more calories from the diet as fat,” says Healthline. “Because of this, low thyroid hormone levels can cause weight gain, even if the number of calories eaten remains constant.”

5. Depression

A 2004 study published by the National Institutes of Health linked hypothyroidism and depression. It’s still very unclear why depression and thyroid hormone levels are linked, but Healthline notes it could be a side effect of an overall decrease in energy and health. On one side, patients who suffer with depression have an increased risk of hypothyroidism, but the opposite was also found true in a study group of 192 people between the ages of 60 and 79-years-old. Approximately 38-percent of participants with hypothyroidism were also found to be clinically depressed or diagnosed with anxiety disorder.

6. Constipation

The onset of constipation is also considered a sign of an underactive thyroid. Many patients complain of irregular, decreased, and even difficult bowel movements that reduce their number 2 bathroom task to only once per week.

7. Hair Loss

Hypothyroidism can cause hair to thin or even fall out in clumps, because like skin cells, our hair follicles are regulated by the thyroid hormone. Someone with a low or inactive thyroid will notice that their hair follicles have stopped or slowed in their regeneration, which is what causes this hair loss. It could be something as subtle as when you comb your hair there is a lot more left in the brush or as drastic as hair falling out in tufts overnight.

8. Is It Chilly In Here?

One of the more common signs of hypothyroidism is cold sensitivity, meaning you’re always chilly, throwing on a blanket or sweater, turning up the thermostat, and wearing fuzzy socks to bed—even when it’s comfortably warm inside. If you have an oral thermometer, scientists from the ATA recommend a simple temperature test, once per week, upon waking. If your temperature is consistently below 98.6-degrees Fahrenheit (considered below normal human body temperature), it may indicate hypothyroidism.

9. Muscle Weakness

The low amount of thyroid hormone in the body causes the body to switch to catabolism, which is defined by Merriam-Webster as “degradative metabolism involving the release of energy and resulting in the breakdown of complex materials (such as proteins or lipids) within the organism).”

Catabolism causes muscle weakness as the body begins to break down muscle tissue. This leads to feelings of weakness and muscle aching. The average person has these feelings after strenuous activity, but for someone who has hypothyroidism, they will experience these symptoms after no activity at all. For example, according to Healthline, “34 percent of low-thyroid individuals get muscle cramps in the absence of recent activity.”

10. Dry and Itchy Skin

Similar to the symptom of hair loss, people who suffer from an underactive thyroid will experience dry and itchy skin, because like hair follicles, skin cells have rapid turnover. When the thyroid isn’t working properly, they aren’t given growth signals from the thyroid hormone, which means it takes much longer for new skin cells to regrow.

“This means the outer layer of skin has been around longer, accumulating damage. It also means that dead skin may take longer to shed, leading to flaky, dry skin,” says Healthline. This source also notes that as long as these skin changes cannot be blamed on allergies, they are likely due to thyroid problems.

11. Trouble Concentrating

According to Healthline, people who have hypothyroidism often complain about not being able to concentrate or a mental “fogginess.” Like all the other symptoms of this list, the degree of which this happens varies individually.

Healthline quotes a 1997 study titled “Do Traditional Symptoms of Hypothyroidism Correlate with Biochemical Disease?” which found that 22 percent of individuals with an underactive thyroid experience difficulty doing everyday math, 36 percent describe not being able to think as fast as usual, and 39 percent have a lower memory. “Although hypothyroidism can cause trouble with memory, the encouraging news is that researches don’t believe it leads to permanent cognitive dysfunction, according to a study published in the journal JAMA Neurology in 2014,” says Everyday Health.

12. Infertility

Women are at a higher risk of having an underactive thyroid. Fortunately, it doesn’t typically develop until after pregnancy or following menopause, because infertility can be one of the symptoms. In an interview conducted by Everyday Health with Gregory Dodell, MD, Assistant Clinical Professor of Medicine, Endocrinology, Diabetes, and Bone Diseases at the Icahn School of Medicine at Mount Sinai in New York City, he confirmed women who suffer from hypothyroidism might experience difficulty getting pregnant and early menopause.

“Therefore, women who are trying to get pregnant or are planning to try and get pregnant in the near future should have their thyroid levels checked. We also monitor women who are being treated for hypothyroidism closely during pregnancy, since the dose of medication may need to be adjusted,” said Dodell.

13. Heavy Periods

Dodell also told Everyday Health that “women may experience a change in their menstrual cycle if their thyroid function is off.” This change includes irregularities and is due to the fact that the thyroid hormone interacts with other hormones that control the menstrual cycle.

In a study conducted way back in 1997, 40-percent of women with hypothyroidism experienced either an increase in menstrual irregularity or heavy bleeding in the frame of a year. This was compared to the 26-percent of women who had the same experience with normal thyroid levels. Healthline also lists another study where “30-percent of women with hypothyroidism had irregular and heavy periods. These women had been diagnosed with hypothyroidism after other symptoms had caused them to get tested.”

14. High Cholesterol

High cholesterol occurs when the thyroid is producing low levels of hormones and high levels of thyroid-stimulating hormone (TSH), which according to Everyday Health, is the hormone “the body produces to stimulate the thyroid gland to secrete more thyroid hormone.”

Two 2012 studies published in the journal Clinical Thyroidology back this claim up when they “found that higher TSH levels were associated with higher cholesterol levels.” Sanjay Dixit, MD, an endocrinologist at the University of Pittsburgh Medical Center told Everyday Health that “minor hypothyroidism, however, usually doesn’t affect cholesterol.”

15. Jaundice

Hypothyroidism is most common in middle-aged and older women, but the Mayo Clinic notes that it can also occur in infants, children, and teens. If a child is born either without a thyroid gland or one that doesn’t work properly, it can be hard to diagnose, because they may not show many symptoms.

The best way to tell is if they start showing signs of jaundice, which presents itself as yellowing of the skin and in the whites of the eyes. “In most cases, this occurs when a baby’s liver can’t metabolize a substance called bilirubin, which normally forms when the body recycles old or damaged red blood cells,” says Mayo Clinic. In addition to jaundice, their face may become puffy, along with their tongue, which creates a choking hazard.

16. Memory Problems

Many patients with hypothyroidism struggle with mental “fogginess” and concentration, which can ultimately lead to issues with memory as well. According to Healthline, in a study of 14 men and women with untreated hypothyroidism, most participants found it challenging to remember verbal cues.

Experiencing trouble with memory can happen to anyone, but if it becomes severe or sudden, this could be a sign of an underactive thyroid.

17. Muscle Aches

Another common symptom of an underactive thyroid is aches in the patient’s muscles and joints. According to Healthline, “A low thyroid hormone flips the metabolic switch toward catabolism, which is when the body breaks down body tissues like muscle for energy.” Muscle strength decreases during catabolism which can lead to feelings of weakness or aches and pains.

It’s typical to feel muscle aches and pains after a strenuous workout, but if you feel this pain without probable cause, it might be a good idea to book an appointment with your physician.

18. Swollen Face

A swollen face is another common symptom of hypothyroidism. Patients have reported that this swelling typically occurs around the eyes, lips, and cheekbones. This symptom is typically a later sign of hypothyroidism and often occurs in tandem with other symptoms including fatigue, weight gain, and constipation.

If you’ve noticed that your face appears more “puffy” or swollen than usual, it could be time to get your thyroid tested.

19. Slow Movements and Thoughts

Patients struggling with an underactive thyroid may notice that their cognitive abilities and movements feel slower. Individuals may feel in a generally weaker state or as though their thinking isn’t as sharp as usual. This can also reflect in movements and energy levels.

fizkes / Shutterstock

20. Trouble Sleeping

Another potential symptom of an underactive thyroid is sudden sleep issues or trouble falling asleep. Thyroid issues affect many bodily processes which can result in both daytime and nighttime symptoms. Often those with an underactive thyroid experience fatigue during the day and difficulty sleeping at night.

“About 30 percent of people with hypothyroidism have sleep apnea,” says Robert S. Rosenberg, DO, medical director of the Sleep Disorders Center of Prescott Valley, Arizona.

MD, Family Medicine, Internal Medicine

Gerald Morris, MD is a family medicine/internal medicine physician with over 20 years expertise in the medical arena. Dr. Morris has spent time as a clinician, clinical research coordinator/manager, medical writer, and instructor. He is a proponent of patient education as a tool in the diagnosis and treatment of acute and chronic medical conditions.

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