Hypothyroidism is the most common type of thyroid disorder. It means your thyroid gland is not active enough. This tiny gland is found in the front of your neck. Its job is to make thyroid hormone. If the gland is underactive, it may not make enough thyroid hormone.

Thyroid hormones control how your body uses energy to do its work. These hormones affect almost every organ in your body. When your thyroid doesn't make enough of these hormones, parts of your body slow down.

The most common cause of hypothyroidism is an autoimmune disorder. This means your immune system sees your normal tissues as strange and starts to attack itself. It makes antibodies against the thyroid gland. The normal thyroid cells are overrun by white blood cells and scar tissue. Another cause may be treatment for an overactive thyroid gland. That may include radioactive iodine therapy or surgery. Hypothyroidism may also develop shortly after pregnancy.

A condition called secondary hypothyroidism can also sometimes happen. It's when your pituitary gland does not make enough thyroid stimulating hormone. The pituitary gland then no longer tells the thyroid gland to make enough thyroid hormones.

Newborns are tested at birth for hypothyroidism. This condition is called congenital hypothyroidism. It must be treated right away. It can affect a baby's brain and nervous system.

You may be more likely to have hypothyroidism if you:

• Are biologically female.
• Are older than age 60.
• Have had thyroid problems or thyroid surgery in the past.
• Have a family history of thyroid problems.
• Have certain conditions, such as type 1 diabetes or rheumatoid arthritis.
• Have Turner syndrome, a genetic condition that affects females.
• Are pregnant or have had a baby within the last 6 months.
• Have an iodine deficiency. Your body needs iodine to make thyroid hormone.

Symptoms are different for each person. They are often hard to notice and start slowly. They may be mistaken for symptoms of depression. Here are the most common symptoms and signs:

• Dull facial expressions
• Tiredness and lack of energy (fatigue)
• Not being able to handle cold
• Hoarse voice
• Slow speech
• Droopy eyelids
• Puffy and swollen face
• Weight gain
• Constipation
• Sparse, coarse, and dry hair
• Coarse, dry, and thickened skin
• Hand tingling or pain (carpal tunnel syndrome)
• Slow pulse
• Muscle cramps
• Joint pain
• Sides of eyebrows thin or fall out
• Confusion
• Increased or irregular menstrual flow

These symptoms may look like other health problems. Always see your doctor for a diagnosis.

Your doctor will ask about your past health. You will also need a physical exam. Blood tests can also help diagnose hypothyroidism. They can measure the amount of thyroid hormone and thyroid-stimulating hormones in your blood. Other blood tests can measure certain substances called antibodies that attack the thyroid gland.

Treatment will depend on your symptoms, age, and general health. It will also depend on how severe the condition is.

The goal of treatment is to return your level of thyroid hormone back to normal. You may need to take medicine that gives you a dose of thyroid hormones. This dose may need to be changed over time. You will likely need to take this medicine for the rest of your life. You will need follow-up blood tests to make sure you are taking the correct dose of thyroid hormone replacement. Always check with your doctor before switching brands of medicine.

If your hypothyroidism is not treated, these complications may happen:

• Anemia
• Low body temperature
• Heart failure
• High (elevated) cholesterol levels

Contact your doctor if your symptoms get worse or you have new symptoms. If you are of childbearing age and want to become pregnant, talk with your doctor first.

• Hypothyroidism means your thyroid gland is underactive. It isn't making enough thyroid hormone. The most common cause is when your immune system starts to attack itself.
• Symptoms include dull facial expressions, tiredness, and weight gain.
• Blood tests help to diagnose this condition. They can measure the amount of thyroid hormone, thyroid-stimulating hormone, and antibodies that attack your thyroid.
• The goal of treatment is to return your levels of thyroid hormone back to normal.
• Untreated hypothyroidism may lead to anemia, low body temperature, and heart failure.
• Treatment may include medicine that replaces lost thyroid hormones. You may need to take thyroid hormones for the rest of your life.

Tips to help you get the most from a visit to your doctor:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your doctor tells you.
• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new directions your doctor gives you.
• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your doctor if you have questions.