By Jillian Foglesong Stabile MD, FAAFP, DABOM
Your thyroid gland is responsible for controlling metabolic function and affects most systems in your body.[1] Abnormalities in thyroid hormone levels can cause a significant number of symptoms that can impact your quality of life. But how do you know if your thyroid is functioning properly? This article will discuss signs of thyroid dysfunction and how to recognize the symptoms.
Functions of the Thyroid Gland
The thyroid gland produces three hormones. The first two, triiodothyronine (T3) and thyroxine (T4) are generally what you think of when you discuss thyroid hormones. The third hormone is calcitonin, which is produced in the C-cells of the thyroid gland and regulates calcium and bone metabolism.[2] T3 and T4 play a role in increasing the basal metabolic rate (BMR), the amount of energy your body uses for basic bodily functions. These thyroid hormones also regulate [1]:
- Body temperature
- Pulse rate and blood pressure
- Digestion rate
- Growth and brain maturation in children
- Concentration
- Reflexes
Thyroid hormones may also affect mental health and cognitive function. People with thyroid dysfunction can display symptoms of psychosis.[3] Thyroid dysfunction can come in various forms.
Signs of Thyroid Dysfunction
There are several forms of thyroid dysfunction, each of which can come with its own signs and symptoms.
Hyperthyroidism
Hyperthyroidism is caused by an overactive thyroid gland. This type of thyroid dysfunction can cause both short-term and long-term health impacts. Some of the symptoms of hyperthyroidism include [4,5]:
- Mood swings and irritability
- Increased feelings of anxiousness
- Difficulty sleeping
- Fatigue
- Weakness
- Intolerance to heat
- Swelling of the thyroid gland (goiter)
- Changes in weight
- Feeling like your heart is racing or beating irregularly
- Bulging eyes
- Bowel changes such as diarrhea
- Problems in pregnancy
Hyperthyroidism can also worsen other chronic conditions as well. Hyperthyroidism can have several causes.
Graves' disease is the most common cause of hyperthyroidism and is a type of autoimmune condition.[4] This type of thyroid dysfunction is around ten times more common in women people assigned female at birth.[6] People with Graves' disease are often hyperthyroid, but late in the condition can have hypothyroidism. Graves' disease may cause symptoms including [7]:
- Changes in weight, usually weight loss
- Increased irritability or anxiety
- Tremors, especially in the hands
- Intolerance of heat
- Goiter
- Abnormal menstrual periods
- Diarrhea or bowel changes
- Changes in energy level, usually fatigue
- Skin changes
- Palpitations
- Insomnia
- Thyroid eye disease (TED), which can cause eye symptoms such as bulging, feeling dry, pressure or pain, puffiness, redness, sensitivity to light, vision loss, or double vision
Toxic multinodular goiter (TMNG) is another potential cause of hyperthyroidism. In this condition, people develop many nodules in the thyroid gland. Nodules larger than 3 cm are more likely to result in the overproduction of thyroid hormones and lead to hyperthyroidism.[5] Similar to TMNG, a single toxic nodule can also cause abnormal thyroid hormone production.
Hyperthyroidism can also be caused by medication or other conditions that can cause inflammation or destruction of the cells responsible for producing thyroid hormone. This can be caused by autoimmune conditions, medications, and even some types of infection.[5]
Hypothyroidism
Hypothyroidism is an underactive thyroid gland. The thyroid doesn't produce enough thyroid hormone. Hypothyroidism is associated with [8]:
- Weight changes (usually gain)
- Muscle and joint aching
- Intolerance to cold
- Changes in hair, such as hair loss or drying
- Changes in menstrual periods
- Dry skin
- Infertility and pregnancy loss
- Depression and other mental health changes
- Memory loss and feelings of brain fog
- Slow heart rate and palpitations (less common)
Hypothyroidism is the most common form of thyroid disease seen and is also more common in women and people AFAB. In severe cases, hypothyroidism can cause severe swelling (myxedema) and send people into a coma.[9] Like hyperthyroidism, there are many potential causes of hypothyroidism.
Like Graves' disease, Hashimoto's thyroiditis is an autoimmune thyroid disease, also called chronic lymphocytic thyroiditis. Hashimoto's is more common in women and people AFAB. Hashimoto's is also more common if you have a family history of the disease.[10] As mentioned, Hashimoto's is an autoimmune disease that can cause inflammation in the thyroid gland. This may initially cause hyperthyroidism, but as the thyroid gland is destroyed by the antibodies, thyroid hormone levels fall. Most of the symptoms of Hashimoto's are the symptoms of hypothyroidism listed above, though even with well-treated Hashimoto's disease and thyroid hormone levels in the normal range, patients with Hashimoto's may still have symptoms.
Other potential causes for hypothyroidism include [11]:
- Surgery on the thyroid gland
- Radiation used to treat cancer of the head or neck or
- Medications
- Congenital hypothyroidism (present from birth)
- Pituitary problems
- Pregnancy
- Iodine deficiency
Iodine deficiency is rare in the United States because foods such as table salt are fortified with iodine. Hypothyroidism is more common in people with other autoimmune diseases such as celiac disease or type 1 diabetes.[11]
Complications of Thyroid Dysfunction
Hyperthyroidism is associated with a number of potential complications. Poorly treated hyperthyroidism can lead to a condition called thyroid storm. Thyroid storm can cause rapid heart rate, diarrhea, shortness of breath, anxiety, fever, and problems in multiple other organs. This condition is life-threatening and needs to be treated immediately or the mortality rate is very high.[5]
Other potential complications of hyperthyroidism include [5]:
- Increased risk of heart attack and stroke
- Abnormal heart rhythms such as atrial fibrillation
- Problems with fertility and pregnancy
- Osteoporosis
Hypothyroidism can also potentially cause long-term complications. The most serious potential complication of hypothyroidism is myxedema coma. This condition is a medical emergency and usually requires admission to intensive care. Even with aggressive care, myxedema coma may cause death up to 60% of the time.[12]
Other complications of hypothyroidism include [11]:
- Goiter
- Heart failure
- High cholesterol
- Peripheral neuropathy
- Infertility
- Birth defects and developmental problems in infants
Thyroid dysfunction can cause significant health concerns; fortunately, testing for thyroid dysfunction is readily available.
Testing for Thyroid Dysfunction
Thyroid hormones can be tested through the blood. The most common types of thyroid testing are thyroid stimulating hormone (TSH), T4, and T3. In certain circumstances, other testing may be indicated, such as thyroid stimulating immunoglobulin (TSI) and thyroid antibodies such as thyroglobulin and thyroid peroxidase. Interpreting thyroid hormone tests can be challenging, and it is important to consult a healthcare provider to determine which tests are necessary and what they may mean. The following table will give you a general idea of what different thyroid test results may mean.
| Condition | TSH level | Free T4 level | Free T3 level | Comments |
|---|---|---|---|---|
| Primary hypothyroidism | High | Low | Low or normal | |
| Subclinical hypothyroidism | High | Normal | Normal | |
| Primary hyperthyroidism | Low | High | High or normal | With Grave’s disease, the TSI will be elevated |
| Mild hyperthyroidism | Low | Normal | Normal | |
| Inflammation of thyroid | Initially low then high | Initially high then low | Varies | Antibody levels can be high |
| Pituitary problems | Low | Low | Low | |
| Peripheral thyroid hormone resistance | High | High | High |
Thyroid testing may be affected by certain substances, including biotin, a common B vitamin that many people take for their hair or nails. Biotin can increase T3 and T4 as well as decrease TSH levels, which can lead to a false diagnosis of hyperthyroidism.[13]
Birth control may also affect thyroid hormone testing by affecting the balance of bound and free thyroid hormones. Birth control won't cause thyroid disease, but it does have the potential to affect the lab results and make diagnosis more difficult.[14]
Pregnancy is another condition that can affect thyroid hormone testing. People with thyroid disease also need to be closely monitored in pregnancy because medication doses often need to be adjusted.[15]
When Should You Test for Thyroid Disease?
If you are having symptoms of hyperthyroidism or hypothyroidism, it is reasonable to get your thyroid hormones tested. The American Thyroid Association recommends checking thyroid hormone levels every five years starting at age 35 in average-risk people, though other groups such as the American Academy of Family Physicians doesn't recommend screening asymptomatic people under age 60.[16] Thyroid hormone testing may also be done at regular intervals in people with known thyroid disease to monitor treatment.
Learn More About Your Thyroid Function with Everlywell
The thyroid gland plays a vital role in multiple aspects of your health. Thyroid dysfunction can make you feel poorly and affect your quality of life. You can check your thyroid hormone levels to keep tabs on your thyroid function and gain valuable insight into your health. Knowing your thyroid function is key to understanding your metabolic health.
Everlywell offers a range of lab tests to guide you in your healthcare journey. With the Everlywell at-home Thyroid Test, you can find out about your thyroid function in a few days with a simple blood sample. If you need help interpreting your results or have further questions, consider a virtual appointment with one of our credentialed healthcare providers.