Hypothyroidism (underactive thyroid)

What is Hypothyroidism?

The thyroid gland is an important organ that regulates metabolism. The thyroid gland makes two forms of thyroid hormone – thyroxine (T4) and triiodothyronine (T3). Hypothyroidism is when the thyroid gland is not producing enough of these hormones. Primary hypothyroidism affects the whole body and may cause a variety of symptoms.

Having too little thyroid hormone can affect the whole body. The body's normal rate of functioning slows, causing mental and physical sluggishness. Symptoms may vary from mild to severe.

What Are Signs and Symptoms Hypothyroidism?

Symptoms are different for each person. They are usually 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 in women

How is Hypothyroidism Diagnosed?

At the UCLA Endocrine Center, you will meet with an endocrinologist who will ask about your past health and perform a comprehensive physical exam.

Blood tests can help diagnose hypothyroidism. Laboratory tests to determine thyroid function include:

Thyroid Stimulating Hormone (aka TSH) helps indicate whether the thyroid is working correctly
Measurements of the two forms of thyroid hormone, T4 and T3

What Causes Hypothyroidism?

The most common cause of hypothyroidism is an autoimmune disorder called Hashimoto’s Thyroiditis. This means your immune system starts to attack itself. It makes antibodies against the thyroid gland. The normal thyroid cells are overrun by white blood cells and scar tissue. Sometimes hypothyroidism occurs after 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 stops working. The pituitary gland then no longer tells the thyroid gland to make thyroid hormones.

There are special considerations for women who have had thyroid disease in the past or currently, and who might be considering pregnancy or are already pregnant. Increased monitoring and adjustment of thyroid-related medications is recommended during this period for the health of both the mother and her baby. Special planning might also be necessary for women with a condition in which thyroid surgery and/or radioactive iodine are required.

Hashimoto’s Thyroiditis

Hashimoto’s thyroiditis is a type of inflammation of the thyroid gland that results from an autoimmune process. It is the most common cause of Hashimoto’s hypothyroidism in the U.S. However, some individuals with Hashimoto's thyroiditis may never develop hypothyroidism and thus never have any symptoms.

How is Hypothyroidism Treated?

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.