If you've been diagnosed with hypothyroidism, you may be confused about what the disease means for you and your health. Hypothyroidism is a condition in which your thyroid gland is underactive, or doesn't make enough of the thyroid hormone. But do you know where your thyroid is or how it's supposed to function? If you don't there's no need to worry: we're here to help.

Hover your mouse over the most commonly used terms to learn what they mean and how they're related to hypothyroidism.


Words You Should Know

Contrast hydrotherapy:

A form of treatment in which hot and cold are alternated as part of the healing process. People with hypothyroidism may alternate hot and cold towels around their necks to increase blood flow and stimulate thyroid function.


A condition in which the thyroid gland does not make enough thyroid hormone.

Underactive or low thyroid:

These are terms used to refer to hypothyroidism.


They are chemical messengers in your body that travel through your bloodstream and affect your tissues and organs.

Thyroid hormones:

These are the hormones responsible for the regulation of metabolism in the body, specifically T4 and T3. Levels are tested through blood screening to determine hypothyroidism.

Thyroxine (T4):

The main hormone secreted by the thyroid. It's inactive until converted by the liver and kidneys. T4 is usually the hormone replaced using medication in someone with hypothyroidism.

Triiodothyronine (T3):

TA secondary hormone secreted by the thyroid.

Pituitary gland:

A gland at the base of the brain that makes, stores, and releases thyroid-stimulating hormone (TSH).

Thyroid-stimulating hormone (TSH):

A hormone that causes the thyroid to release T3 and T4 hormones.

Endocrine disorder:

A disease in which hormone levels are too low or too high. Hypothyroidism is an endocrine disorder.


A specially trained doctor who deals with metabolic disorders such as hypothyroidism.


It is the way that cells in your body use energy, for example, burning calories, breathing, circulating blood, and processing your food.


Hypothyroidism is a deficiency of the production of thyroid hormones.


It is swelling and inflammation that damages the thyroid gland.


A general feeling of tiredness, which is a symptom of hypothyroidism.


It is reduced strength in one or more muscles and a symptom of hypothyroidism.

Weight gain:

It is increased body weight — particularly fatty tissue — and a symptom of hypothyroidism.

Hair loss:

Hair loss may be symptomatic of hypothyroidism. Excessive hair loss from the scalp is known as baldness.

Dry skin:

It is itching, red, cracked or flaky skin, which may be a symptom of hypothyroidism.

Cold intolerance:

Extreme sensitivity to cold temperatures or feeling cold more often is a symptom of hypothyroidism.

Muscle aches:

Soreness, tenderness, or pain in muscles, even while at rest, may be symptomatic of hypothyroidism.


A decrease in heartbeat below the average of 60 to 100 beats per minute. People with hypothyroidism typically have 10 to 20 fewer beats per minute.

Shortness of breath:

It is also known as dyspnea. This may result from weakened skeletal muscles in people with hypothyroidism.


Infrequent bowel movements or difficulty passing stools are symptoms of constipation. These symptoms are due to slowed metabolism in people with hypothyroidism.


A feeling of sadness or being "down" that can result from lower T3 levels in those with hypothyroidism.


The tendency to be quick to anger or become overly upset. This may be a symptom of hypothyroidism.

Memory loss:

Unusual forgetfulness may be a symptom of hypothyroidism.

Carpal tunnel syndrome:

Pain and numbness in the wrist and hand. Although very rare, this occurs in hypothyroidism as a result of swollen membranes placing pressure on the nerves. It can indicate hypothyroidism that has been long untreated.

Abnormal menstrual cycles:

Women with hypothyroidism may experience irregular periods. This can mean excessive menstrual bleeding that lasts longer and occurs more frequently or periods that are infrequent or absent.

Decreased libido:

Decreased desire to engage in sexual activity is a symptom of hypothyroidism.


It's the abnormal enlargement of the thyroid gland, often observable to the naked eye as a large mass on the neck. A goiter can impact thyroid function and contribute to hypothyroidism.


A nodule is the enlargement of just one part of the thyroid gland, which appears as a lump. It can impact thyroid function and contribute to hypothyroidism.


It's a synthetic thyroid hormone used to treat hypothyroidism. People with hypothyroidism take a small pill containing levothyroxine once a day to treat the condition.


It's an element needed for the production of thyroid hormones. The required amount is typically met by eating a normal Western diet.

Myxedema coma:

It refers to the loss of brain function resulting in a coma. It is the result of severe hypothyroidism that has gone untreated for a long time.

Thyroid ultrasound:

A diagnostic test used to view the thyroid. It's useful in determining the presence of nodules or irregularities in the thyroid gland.

Blood tests:

Blood work is done regularly in people with hypothyroidism to ensure that replacement therapy is at normal levels.


They are vitamins and herbs used to enhance a diet. They can impact a person's absorption and response to thyroid medications and should be discussed with a healthcare provider.


A gland located at the front of the neck, just above where your collarbones meet. It secretes hormones that regulate your metabolism.

Bradycardia Deficiency Hair loss Hypothyroidism Underactive or
low thyroid
Thyroid Hormones Thyroid
Thyroxine (T4) Triiodothyronine
Pituitary gland Thyroid-stimulating
hormone (TSH)
Endocrinologist Metabolism Thyroiditis Fatigue Weakness Weight gain Dry skin Muscle
of breath
Constipation Depression Irritability Memory
Carpal tunnel
menstrual cycles
Goiter Nodule Levothyroxine Iodine Myxedema
Blood tests Supplements Contrast
Cold intolerance