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12 Surprising Symptoms of an Underactive Thyroid

Unexpected ways your thyroid can impact your health.
12 Surprising Symptoms of an Underactive Thyroid
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The thyroid is the butterfly-shaped gland at the base of your neck. Its job is to regulate the body’s metabolism in the form of blood pressure, blood temperature, and heart rate.

When your thyroid hormone production drops, your body processes slow down and change, affecting virtually every system in your body. Undiagnosed thyroid disease puts patients at risk for other ailments, such as cardiovascular diseases, osteoporosis, and infertility.

The list of symptoms of hypothyroidism is surprisingly long. But symptoms vary from person-to-person, and there are some that you may not suspect.

Check out these 12 lesser-known symptoms:

1. Headaches

The Journal of Headache and Pain found a high prevalence of hypothyroidism in those who experience migraine headaches. Around 30% of people with an underactive thyroid experience headaches. It's still unclear whether hypothyroidism is the cause of headaches, though this is a reasonable assumption since an underactive thyroid may slow blood circulation to the brain. Additionally, fatigue, a common symptom of hypothyroidism, is often associated with migraines and may play a role in triggering migraine headaches.

2. Memory Changes

Overt hypothyroidism (characterized by an increased TSH and decreased T4 level) may negatively affect several cognitive functions. These may include but are not limited to attention and concentration, memory, perceptual function, language, psychomotor function, and executive function. This troubling symptom is mostly reversible with levothyroxine treatment.

Mild hypothyroidism (characterized by an increased TSH only), on the other hand, is not associated with significant cognitive decline. Patients with mild (or subclinical) hypothyroidism may experience "brain fog," which is a subtle decline in planning, memory, attention and concentration, or multitasking ability.

3. Mood Swings

Low thyroid hormone levels may contribute to depression and sadness. Thyroid hormones control our body's metabolism and energy production. Without proper levels, mental health symptoms such as depression, anxiety, mood swings, and brain fog may become more noticeable.

Alternatively, symptoms of overt hypothyroidism, such as slowed thought and speech, decreased attentiveness, or apathy, mimic the symptoms of depression. These similarities sometimes lead to missed diagnosis or misdiagnosis of clinical depression.

Try this questionnaire to check your own symptoms: 

4. Digestive Issues

Your digestive system can be impacted by thyroid health in different ways. Too little thyroid hormone slows the movement of food through your digestive tract, which can leave your belly bloated or contribute to constipation. It also slows the body's metabolism, which can lead to weight gain.

In more severe cases, illnesses such as Irritable Bowel Syndrome (IBS) and Small Intestinal Bacterial Overgrowth (SIBO) can develop. Getting these issues diagnosed and treated will also greatly help in managing your thyroid issues.

5. Heartburn

Research suggests that overt hypothyroidism may be associated with an esophageal motility disorder that presents as heartburn. What is esophageal motility, you ask? John Hopkins Medicine explains this as the contractions that occur in the esophagus, the muscular tube that propels food from the throat to the stomach. Esophageal dysmotility is when contractions in the esophagus become irregular.

It's unclear exactly why thyroid hormones may have this effect on the esophagus. Perhaps a slowed digestive system could lead to acid reflux and heartburn, or a food sensitivity (like gluten) could be to blame.

6. Dry Skin

Low thyroid hormone levels directly affect the skin, causing a variety of changes, including dryness, thickening, and scaling. Patients can suffer from head (dry, flaky scalp) to toe (dry and cracked feet) and everywhere in between.

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7. Sensitivity to Cold

The inability to tolerate cold weather, to the point where you are shaking even when bundled up in the winter, is another symptom of hypothyroidism. You may notice that your hands and feet are frequently cold, and it can be difficult to warm them up due to decreased circulation.

The hypothalamus in the brain essentially acts as a thermostat. It directs the thyroid gland to increase or decrease your body's metabolism to regulate body temperature. The thyroid needs to function appropriately to burn calories in the body to create heat and fuel.

8. Menstrual Irregularities

Hypothyroidism may cause several menstrual irregularities, from heavy, prolonged periods to infrequent or absent. The American College of Obstetricians and Gynecologists defines heavy menstrual bleeding as:

  • Bleeding that lasts more than seven days
  • Bleeding that soaks through one or more tampons or pads every hour for several hours in a row
  • Needing to wear more than one pad at a time to control flow
  • Needing to change pads or tampons during the night
  • Menstrual flow with blood clots that are as big as a quarter or larger

If you experience heavy bleeding, you may want to visit your gynecologist to determine what's going on. Tests like a pelvic exam, ultrasound, or TSH blood test may help with a diagnosis.

Possibly more common is absent or infrequent menstruation, which can occur from the possible increase in thyrotropin-releasing hormone (TRH) in those with underactive thyroid function. TRH releases from the hypothalamus, which then triggers the release of thyroid-stimulating hormone (TSH) and prolactin from the pituitary gland. Too much prolactin, often referred to as the "milk hormone," can interfere with estrogen production, causing infrequent or absent periods, unwanted milk production, and symptoms of menopause.

Of course, while hypothyroidism is one potential cause of menstrual irregularities, there are other possible diagnoses, and you should consult with your care team.

9. Fertility Issues

Many of our hormones are part of a regulatory hormonal cascade, so when thyroid hormone production drops, luteinizing hormone (LH) levels may also remain low. LH helps to regulate the menstrual cycle and egg production; therefore, ovulation may not occur or may not happen with any regularity.

Irregular ovulation may make it difficult to get pregnant. Normal thyroid function is necessary for fertility and a healthy pregnancy, and you should test your thyroid function if:

  • You plan to get pregnant
  • Have a history of thyroid problems or irregular periods
  • Have miscarried
  • Are unable to conceive after one year of unprotected sex

This thyroid evaluation should include TSH, T4, T3, and TPO antibodies. Thyroid antibodies are not always included in the initial fertility workup, though it is important because their presence may double the risk of recurrent miscarriage.

10. Muscle Aches & Weakness

A recent study shows that 79% of patients with hypothyroidism experience muscle pain and weakness, confirmed by an increase of creatine kinase (CK) in patient's blood. CK is an enzyme found in the heart, brain, skeletal muscle, and other tissues that increases when there is muscle damage. Locations of pain and weakness may vary but are thought to be most common in the shoulder and hip areas. Cramping can also be a problem, as well as Carpal Tunnel Syndrome. Untreated hypothyroidism may lead to significant muscle disease, causing severe functional limitations.

11. Thinning Hair

A very frustrating symptom for women with thyroid disease can be thinning hair or hair loss. Similarly, you may experience thinning of your eyebrow hair, especially on the outer third of your brow.

When the thyroid doesn't function properly, the body does not get the energy it needs for all of its normal bodily functions. This slowdown includes follicle stimulation. Untreated hypothyroidism can lead to hair loss. Because the severity of symptoms can vary, it's possible not even to realize you're losing hair because it falls out so sparsely and uniformly. It may be three to four months after the onset of hypothyroidism before noticing hair loss due to the long hair cycle.

12. Throat Tightness

Inflammation or swelling of the thyroid gland can cause tightness to occur in your throat. It may feel like when you wear a turtleneck or a tight collar on your shirt. You may also notice a difficulty swallowing. You can perform a simple at-home neck check to help with early detection. A self-exam can help you find lumps or enlargements that may indicate a thyroid condition.

If you have persistent symptoms as described above, a thyroid blood test can help you understand how your thyroid is functioning and determine if there is a need for further evaluation by a thyroid doctor.

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Julia Walker, RN, BSN

Clinical Nurse

Julia Walker, RN, BSN, is a clinical nurse specializing in helping patients with thyroid disorders. She holds a Bachelor of Science in Nursing from Regis University in Denver and a Bachelor of Arts in the History of Medicine from the University of Colorado-Boulder. She believes managing chronic illnesses requires a balance of medical interventions and lifestyle adjustments. Her background includes caring for patients in women’s health, critical care, pediatrics, allergy, and immunology.

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