What is thyroid disease?

Thyroid disease is a general term for a medical condition that keeps your thyroid from making the right amount of hormones. It can affect people of all ages.

Your thyroid is a small, butterfly-shaped gland located at the front of your neck under your skin. It’s a part of your endocrine system and controls many of your body’s important functions by producing and releasing thyroid hormones, like thyroxine (T4) and triiodothyronine (T3).

Your thyroid’s main job is to control the speed of your metabolism (metabolic rate). This is the process of how your body transforms the food you consume into energy. All the cells in your body need energy to function. When your thyroid isn’t working properly, it can impact your entire body.

Types of thyroid disease

The two main types of thyroid disease are hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid). But they each have several conditions that can cause them.

Conditions that can cause hypothyroidism include:

• Hashimoto’s disease: This is a lifelong (chronic) autoimmune condition that can cause an underactive thyroid. It’s the most common cause of hypothyroidism in countries with widely available iodized salt and other iodine-enriched foods.
• Iodine deficiency: Your thyroid needs iodine to make thyroid hormone, so a lack of the mineral in your diet can lead to hypothyroidism. It’s the most common cause of   in countries that don’t have iodized salt widely available. It often causes goiter (enlarged thyroid).
• Congenital hypothyroidism : Sometimes, babies are born with a missing or underactive thyroid. “Congenital” means “present from birth.” About 1 in every 2,000 to 4,000 babies have congenital hypothyroidism.

Conditions that can cause hyperthyroidism include:

• Graves’ disease: This is a chronic autoimmune condition that causes an overactive thyroid. It’s the most common cause of hyperthyroidism.
• Thyroid nodules: These are abnormal lumps on your thyroid gland. If the nodules are hyperfunctioning, they can lead to hyperthyroidism.
• Excessive iodine: When you have too much iodine in your body, your thyroid makes more thyroid hormones than you need. You may develop excessive iodine by taking certain medications, like amiodarone (a heart medication).

Conditions that can cause both hypothyroidism and hyperthyroidism at different times include:

• Thyroiditis: This is inflammation (swelling) of your thyroid gland. It typically causes temporary  hyperthyroidism at first and then temporary or chronic hypothyroidism Postpartum thyroiditis: This is a relatively rare condition that affects some birthing parents after pregnancy. An estimated 5% of people may experience this in the year after giving birth. It typically causes hyperthyroidism first, followed by hypothyroidism. It’s usually temporary.

How common is thyroid disease?

Thyroid disease is very common. About 20 million people in the United States have some type of thyroid condition.

What are the symptoms of thyroid disease?

There are a variety of symptoms you could experience if you have thyroid disease. Unfortunately, symptoms of a thyroid condition are often very similar to the signs of other medical conditions and stages of life. This can make it difficult to know if your symptoms are related to a thyroid issue or something else entirely.

For the most part, the symptoms of thyroid disease can be divided into two groups — those related to having too much thyroid hormone (hyperthyroidism) and those related to having too little thyroid hormone (hypothyroidism). The symptoms are often “opposites” between the two conditions. This is because hyperthyroidism speeds up your metabolism, and hypothyroidism slows down your metabolism.

Symptoms of hypothyroidism include:

• Slower-than-usual heart rate.
• Feeling tired (fatigue).
• Unexplained weight gain.
• Feeling sensitive to cold.
• Dry skin and dry and coarse hair.
• Depressed mood.
• Heavy menstrual periods (menorrhagia).

Symptoms of hyperthyroidism include:

• Faster-than-usual heart rate (tachycardia).
• Difficulty sleeping.
• Unexplained weight loss.
• Feeling sensitive to heat.
• Clammy or sweaty skin.
• Feeling anxious, irritable or nervous.
• Irregular menstrual cycles or a lack of periods (amenorrhea).

Both conditions can cause an enlarged thyroid (goiter), but it’s more common in hyperthyroidism.

What are the risk factors for thyroid disease?

You may be at a higher risk of developing a thyroid condition if you:

• Are assigned female at birth (AFAB). People AFAB are five to eight times more likely to have a thyroid condition than people assigned male at birth (AMAB).
• Have a family history of thyroid disease.
• Have Turner syndrome.
• Take a medication that’s high in iodine.
• Live in a country or area that doesn’t have iodized table salt, which can lead to iodine deficiency.
• Are older than 60, especially if you’re AFAB.
• Have received radiation therapy to your head and/or neck.

Having an autoimmune disease also increases your risk, especially if you have:

• Pernicious anemia.
• Type 1 diabetes.
• Celiac disease.
• Addison’s disease (primary adrenal insufficiency).
• Lupus.
• Rheumatoid arthritis.
• Sjogren’s syndrome.

How is thyroid disease diagnosed?

Your healthcare provider will start by asking about your symptoms and medical history and doing a physical exam. During the exam, they’ll gently feel your thyroid gland to check if it’s enlarged or if there are noticeable nodules.

Your provider will need to use some thyroid tests to confirm a diagnosis. These include:

• Blood test: These tests can tell you if you have hypothyroidism or hyperthyroidism. There are several types of thyroid blood tests, including thyroid simulating harmones TSH, T3 and T4, and thyroid antibodies.
• Imaging tests: Imaging tests, like a thyroid ultrasound, help your provider look for nodules (lumps) and/or goiter. Nuclear medicine imaging like a thyroid uptake and scan can help show if nodules are overactive.