Endocrinology and Diabetes
Hypothyroidism (Underactive Thyroid)
We help you manage an underactive thyroid to keep you leading a healthy, active life.
Medically reviewed by Jose Joaquin Lado Abeal, M.D. on Nov. 19, 2024.
What Is Hypothyroidism?
Hypothyroidism is an underactive thyroid gland. The thyroid is a butterfly-shaped gland in your neck. It makes and releases hormones that your body needs for many important functions.
With hypothyroidism, the thyroid does not create enough of a hormone called thyroxine (T4). Bodily functions such as your breathing, heart rate and metabolism can slow down. In most cases, hypothyroidism is a lifelong condition.
At UC Davis Health, our hormone specialists diagnose and treat an underactive thyroid as soon as possible. You can find expert care in our Division of Endocrinology, Diabetes and Metabolism.
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Symptoms of a Hypoactive Thyroid
Low thyroid hormone levels can cause a range of symptoms. People with hypothyroidism tend to have mild symptoms that may not obviously point to an underactive thyroid.
Common Symptoms
Talk with your provider if you experience any symptoms of hypothyroidism, such as:
- Changes in your menstrual cycle
- Constipation
- Extreme tiredness
- Feeling cold all the time or sensitivity to cold
- Hair loss
- Hoarse voice
- Lack of sweat
- Muscle cramps
- Swelling or puffiness in your face
- Trouble sleeping
- Unexplained weight gain
Emergency Symptoms
Extremely severe hypothyroidism, called myxedema crisis, needs emergency treatment. Seek medical help if you experience:
- Loss of consciousness
- Low blood pressure
- Low blood sugar
- Low body temperature
- Slowed breathing
- Strange changes in mood or behavior
Causes of an Underactive Thyroid
Sometimes people are born with an underactive thyroid, a condition called congenital hypothyroidism. Other people develop the condition later in life for a range of reasons, including:
Hashimoto’s Disease
Hashimoto’s disease causes your immune system to attack your thyroid. It leads to inflammation that keeps your thyroid from making thyroid hormones.
Medications
Certain medications may affect how your thyroid works. Your provider can review and adjust your medications to bring your thyroid hormone levels back to normal.
Other Autoimmune Diseases
Inflammation from autoimmune diseases such as rheumatoid arthritis, lupus or type 1 diabetes can cause hypothyroidism.
Pituitary Diseases
The pituitary gland plays a role in making your thyroid create thyroid hormones. Diseases that affect how well your pituitary gland works can cause hypothyroidism.
Pregnancy
Some people develop an underactive thyroid after pregnancy and giving birth. Postpartum hypothyroidism usually goes away with treatment and time.
Smoking
The nicotine in cigarettes can cause long-term changes to how your body produces thyroid hormone.
Thyroid Removal or Radiation Therapy
Surgery or radiation therapy to treat thyroid diseases — such as thyroid cancer or nodules (growths) — lead to low levels of thyroid hormone. Some procedures remove the thyroid completely Others may only destroy harmful cells or remove parts of the gland.
Viral Infections
Viral illnesses can affect your thyroid and lower your thyroid hormone levels. This form of hypothyroidism usually goes away over time.
Risk Factors for an Underactive Thyroid
Certain factors increase your risk of developing an underactive thyroid, including:
Age
People older than 60 face a higher risk.
Biological Sex
Women are more likely than men to develop hypothyroidism.
Certain Health Conditions
You face a higher risk for hypothyroidism if you have an autoimmune disease or Turner’s syndrome.
Family History
Hypothyroidism can run in families. Having a family member with the condition can increase your risk.
Past Radiation Therapy
Receiving radiation therapy to your thyroid or nearby areas, including your neck and chest, can increase your risk.
Previous Thyroid Disorders and Treatment
Your chances of developing hypothyroidism increase if you have had other issues with your thyroid. Any past treatments for thyroid disorders can also increase your risk for an underactive thyroid.
Pregnancy
Pregnancy can place you at a higher risk for an underactive thyroid during postpartum time.
Diagnosis and Testing for Low Thyroid Hormone
We do a complete evaluation to check for hyperthyroidism and low thyroid hormone levels. Our endocrinologists know what symptoms, signs and test results to look for.
Your provider will do a physical exam to check for signs of an underactive thyroid and an enlarged thyroid gland. They will also review your medical history to understand any existing conditions and medications you take.
We also get several blood tests to help diagnose hypothyroidism, including:
- Thyroid-stimulating hormone (TSH) test: TSH is a hormone that your pituitary gland makes. It signals to your thyroid to produce thyroid hormone. A TSH test shows the amount of TSH in your blood. More TSH means you don’t have enough thyroid hormone.
- Thyroxine (T4) test: A T4 test measures the amount of the thyroid hormone thyroxine in your blood.
- Thyroid antibody test: An antibody test can check for autoimmune diseases that cause hypothyroidism.
Hypothyroidism Treatments
At UC Davis Health, our endocrinologists offer expert thyroid care. We strive to restore your thyroid health and help you feel like yourself again.
Medication is the main treatment to control hypothyroidism. The medication has a synthetic (artificial) form of thyroid hormone.
You will need to take the thyroid replacement medication daily to keep your thyroid hormone healthy. Our endocrinologists figure out what dose works best for you. We work with you to understand and manage any side effects while optimizing your well-being.
Your treatment plan may include:
Thyroid Hormone Replacement
We prescribe a medication that gives your body the thyroid hormone it needs. The medication, called levothyroxine, is taken daily and in pill form. In emergency cases, you may need a levothyroxine injection.
Physical Exams
During routine physical exams, we check for signs of abnormal thyroid hormone levels. Signs such as an enlarged thyroid gland or changes to your movement may mean we need to adjust your medication.
Blood Tests
We test your blood for TSH or thyroid hormone at least once a year to ensure your levels are normal. We do more frequent blood tests early on in your treatment. As needed, we adjust your medication based on the results.
Who does it affect?
5 in 100People in the United States older than 11
Most common age
60+Hypothyroidism most commonly develops in people older than 60.
Source: National Institute of Diabetes and Digestive and Kidney Diseases: Hypothyroidism (Underactive Thyroid)
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