Hypothyroidism: What You Need to Know

What is hypothyroidism?

Also known as an underactive thyroid, hypothyroidism occurs when your thyroid doesn't produce enough thyroid hormones to help other systems in your body function properly.

For many people, hypothyroidism can go unnoticed in its early stages. The good news is that hypothyroidism can be treated by taking regular medications, having blood work performed, and scheduling follow-up appointments with your doctor as directed. When left untreated, however, hypothyroidism can lead to several other health conditions, both minor and severe, including weight gain, hair loss, infertility, and heart disease.

What does your thyroid do?

The thyroid gland is a small, butterfly-shaped organ located in the front of the neck. Like other glands in your body, your thyroid is responsible for creating and releasing hormones that help different systems in your body function, enabling it to use energy. Your thyroid affects your weight, heart rate, digestion, and mood, among other vital bodily functions.

Thyroid disease occurs when the thyroid does not function properly, releasing too many or too few hormones. There are many variations of thyroid disease, including hypothyroidism, hyperthyroidism, Hashimoto's disease, and thyroiditis.

If you are diagnosed with thyroid disease, it's important to take it seriously. Finding an experienced medical team to help treat and manage your condition is important to ensure your long-term health.

What's the difference between hypothyroidism and hyperthyroidism?

The difference between hypothyroidism and hyperthyroidism lies in the amount of thyroid hormone that your body produces. In hypothyroidism, your thyroid doesn't make enough thyroid hormone, which can slow down your metabolism. On the other hand, your thyroid makes too much thyroid hormone if you have hyperthyroidism, causing your metabolism to speed up.

In many ways, these two thyroid conditions cause opposing symptoms. Hypothyroidism can make you sensitive to cold, while hyperthyroidism can make you sensitive to heat. Hypothyroidism can cause you to gain weight, while hyperthyroidism can make gaining weight difficult.

Both of these conditions can lead to a number of symptoms, ranging from minor to severe, and impact the proper function of normal bodily functions. For these reasons, treating either condition is critical.

Other related conditions


The symptoms of hypothyroidism can vary from person to person, depending on how low your thyroid hormone levels are. Typically, the signs of hypothyroidism develop slowly over time, sometimes over many years.

In its earliest stages, you may notice symptoms, including fatigue and weight gain, that can be attributed to other health conditions or life circumstances, including simply getting older. If the symptoms result from hypothyroidism, they will likely worsen and become more obvious over time.

Common symptoms of hypothyroidism include:¹

  • Weight gain

  • Fatigue

  • Dry skin

  • Constipation

  • Sensitivity to cold

  • Hair loss or thinning

  • Joint pain or stiffness

  • Puffy face

  • Depression

  • Muscle weakness

  • Muscle aches

  • Irregular menstrual cycles

  • Slowed heart rate

  • Memory loss

  • Enlarged thyroid gland (goiter)

  • Infertility

If you notice one or more symptoms of hypothyroidism, it's important to seek medical attention immediately. If left untreated, hypothyroidism can lead to more serious health conditions, impacting how you look and feel and, most importantly, your long-term health.

For instance, hypothyroidism can lead to high cholesterol and even myxedema coma, in which your normal bodily functions slow down to a point where your life is put at risk.

Untreated hypothyroidism can lead to complications for pregnant women, including premature birth, fetal growth and development issues, and miscarriage.

  1. Hypothyroidism (underactive thyroid) | National Institute of Diabetes and Digestive and Kidney Diseases


The two main hormones produced by your thyroid are triiodothyronine (T3) and thyroxine (T4). Along with controlling your body temperature and heart rate, these hormones help you maintain a healthy metabolism. When either of these hormones is out of balance, it can significantly impact your overall health.

Hypothyroidism can result from a variety of factors, including:

Thyroid surgery (thyroidectomy)

Removing some or all of your thyroid gland can cause your thyroid hormone production to decrease or stop altogether. People missing some or all of their hormones will have to take a replacement thyroid hormone for the rest of their lives to maintain healthy T3 and T4 levels.

Autoimmune disease

Hashimoto's thyroiditis is an autoimmune disease that is the most common cause of hypothyroidism.² It occurs when your body creates antibodies that attack your thyroid gland, preventing it from working as it should.

Radiation therapy

In some cases, radiation therapy used to treat cancer of the head, neck, or thyroid can lead to hypothyroidism.

Certain medications

Medications, such as lithium used to treat psychiatric disorders, can prevent the thyroid from producing enough hormones.

A side effect of hyperthyroidism treatment

People who produce too many thyroid hormones (hyperthyroidism) are often given anti-thyroid medications. Sometimes, these can harm the thyroid and prevent it from ever making an adequate amount of thyroid hormones again.

Congenital hypothyroidism

In rare cases, babies are born with a low functioning thyroid that lasts throughout their lives.

Who is at risk of developing hypothyroidism?

For many people, preventing thyroid disease, including hypothyroidism, is impossible. While this is true, some factors make some people more likely to develop hypothyroidism than others. These include:

  • Women

  • People over the age of 60

  • Those with  a family history of thyroid disease

  • Women who are pregnant or who are up to 6 months postpartum

  • Those who have type 1 diabetes

  • People with lupus

  • People with rheumatoid arthritis

  • Those with a history of thyroid problems, such as a goiter or thyroid surgery

  • People treated with radioactive iodine or anti-thyroid medications

How is hypothyroidism diagnosed?

Hypothyroidism must be diagnosed by your doctor. If you're experiencing one or more of the signs of hypothyroidism, your doctor may use a variety of tests and techniques to determine their cause. In some cases, your doctor may diagnose you with hypothyroidism before you ever experience symptoms.

Your doctor may diagnose you with hypothyroidism after:

  • Asking about your symptoms and medical history

  • Performing a physical exam

  • Doing blood work to test your T3, T4, and TSH (thyroid-stimulating hormone) levels

  • Using an ultrasound machine to look at the size and condition of your thyroid gland

Be sure to tell your doctor about any symptoms you're experiencing, as well as your family medical history and any medications you're taking. It's important to note that some medications can alter the results of blood tests used to check thyroid hormone levels, including heparin used as blood thinner and biotin, which is in many multivitamins.

  1. Hashimoto's disease | National Institute of Diabetes and Digestive and Kidney Diseases


Most patients with a hypothyroidism diagnosis need to take a daily dose of synthetic thyroid hormone levothyroxine, such as Synthroid. Synthetic thyroid hormone is taken orally and can restore healthy hormone levels. It usually reverses the negative symptoms of hypothyroidism, including fatigue and hair loss.

If hypothyroidism is causing you to feel weak or tired, you'll likely feel back to normal soon after taking a synthetic thyroid hormone medication. However, for some people, it can take months for symptoms to subside.

Most people with hypothyroidism can expect to take a replacement thyroid hormone medication for the rest of their lives. However, your dosage may need to be adjusted at different times, so your doctor will likely check your TSH levels at least yearly, depending on your symptoms.

Finding the right dosage of levothyroxine

When you begin taking levothyroxine, it's normal for your doctor to check your TSH levels every six to eight weeks through blood work. If your dosage is too high, you may experience one or more of the following side effects:

  • Insomnia

  • Heart palpitations

  • Anxiety

  • Shakiness

  • Increased appetite

  • Weight loss

Levothyroxine is an inexpensive medication with virtually no side effects when taken correctly. It's important to let your doctor know if you switch brands of levothyroxine, as this may require a change in dosage.

It's never a good idea to skip a dose or stop taking levothyroxine just because you start to feel normal again. If you do, your hypothyroidism symptoms could gradually return.

Promoting proper absorption of levothyroxine

Consuming different foods, supplements, and vitamins can affect your body's ability to absorb levothyroxine properly. Be sure to let your healthcare provider know if you eat a lot of high-fiber or soy products, as well as if you take other medications or supplements, including:

  • Calcium

  • Iron

  • Aluminum hydroxide (found in some antacids)

It's recommended that levothyroxine be taken at the same time every day on an empty stomach. Most people find that the best time to take levothyroxine is when they wake up and then wait an hour to eat or take other medications. If you prefer to take it at night, be sure to wait at least four hours after eating a snack or meal. If you miss a dose of levothyroxine, simply resume with your regular dose the next day.

Doctors & specialists

Once you first notice the signs of hypothyroidism, you'll likely begin your journey to recovery by making an appointment with your primary healthcare provider or family doctor. If your doctor suspects that you have thyroid disease or confirms it through blood tests, they’ll likely refer you to a doctor who specializes in thyroid conditions, called an endocrinologist.

Infants, children, and teenagers will need to see a pediatric endocrinologist to ensure their treatment and levothyroxine dosage is catered to their health needs.

To help you prepare for your appointment with your doctor, keep these tips in mind:

  • Ask the doctor's office if there are any steps you need to take before arriving for your appointment.

  • Write down any symptoms you have been or are currently experiencing, even if you think they are unrelated to your thyroid.

  • Write down any recent causes of stress in your personal life that may be relevant to your condition, such as changes at work or home.

  • Write down all current medications you're taking, including supplements and vitamins.

  • Write down questions you have for the doctor about your symptoms or treatment.

  • Bring a friend or family member with you who can remind you of things you forget and listen to the doctor's instructions.

Bringing a list of questions to ask your doctor about hypothyroidism is one of the most proactive steps you can take to receive the appropriate care, improve your symptoms, and restore your health as quickly as possible. Here are some helpful questions to ask your doctor during your appointment:

  • What do you suspect is causing my symptoms?

  • What tests do you recommend I have done?

  • What treatment options are available? Which do you recommend?

  • Should I see an endocrinologist? Why or why not?

  • Will this diagnosis affect my other health conditions? If so, how?

  • Are there lifestyle changes I need to make?

  • Is there a generic option for the medication you're prescribing?

  • What literature or websites do you recommend to teach me more about hypothyroidism?

  • Is this condition temporary or long-term?

Your healthcare provider is likely to have a number of questions for you as well. Make sure to answer any questions they may have so they know exactly what your condition is and any possible causes. Some questions your doctor is likely to ask you include:

  • When did your symptoms begin?

  • Have your symptoms happened on and off or consistently?

  • Are your symptoms mild or severe?

  • Does anything improve your symptoms?

  • Does anything seem to make your symptoms worse?

  • Does thyroid disease run in your family?