Hypothyroidism results from failure to maintain adequate tissue levels of thyroid hormone.
Hypothyroidism is divided into primary hypothyroidism (failure of the thyroid gland to produce hormones). Secondary hypothyroidism (the thyroid gland is normal and the pituitary fails to secrete adequate thyrotropin [TSH]) and tertiary hypothyroidism (failure to secrete thyrotropin releasing-hormone [TRH]). Cretinism refers to congenital hypothyroidism, and myxedema coma refers to the most severe form of hypothyroidism.
Your thyroid is a butterfly-shaped gland located at the base of your neck, just below your Adam's apple. Although it weighs less than an ounce, the thyroid gland has an enormous effect on your health. All aspects of your metabolism, from the rate at which your heart beats to how quickly you burn calories, are regulated by thyroid hormones.
As long as your thyroid releases the proper amounts of these hormones, your system functions normally. But sometimes your thyroid doesn't produce enough hormones, upsetting the delicate balance of chemical reactions in your body. This condition is known as hypothyroidism.
Signs and symptoms
The signs and symptoms of hypothyroidism vary widely, depending on the severity of the hormone deficiency. But in general, any problems you do have tend to develop slowly, often over a number of years.
At first, you may barely notice symptoms such as fatigue and sluggishness, or you may simply attribute them to getting older.
But as your metabolism continues to slow, you may develop more obvious signs and symptoms, including:
When hypothyroidism isn't treated, symptoms can gradually become more severe. Constant stimulation of your thyroid to release more hormones may lead to an enlarged thyroid (goiter). In addition, you may become more forgetful, your thought processes may slow or you may feel depressed.
Advanced hypothyroidism, known as myxedema, is rare, but when it occurs it can be life-threatening. Symptoms include drowsiness and intense intolerance to cold followed by profound lethargy and unconsciousness. In some cases, myxedema can be fatal.
Hypothyroidism in children and teens
As the disease progresses, infants are likely to have trouble feeding and may fail to grow and develop normally. They may also have:
Left untreated, even mild hypothyroidism in infants can lead to severe physical and mental retardation.
In general, children and teens who develop hypothyroidism have the same signs and symptoms as adults do, but they may also experience:
Your thyroid gland produces two main hormones, thyroxine (T-4) and triiodothyronine (T-3). They maintain the rate at which your body uses fats and carbohydrates, help control your body temperature, influence your heart rate and help regulate the production of protein. Your thyroid gland also produces calcitonin, a hormone that regulates the amount of calcium in your blood.
The rate at which thyroxine and triiodothyronine are released is controlled by your pituitary gland and your hypothalamus — an area at the base of your brain that acts as a thermostat for your whole system. Here's how the process works:
The hypothalamus signals your pituitary gland to make a hormone called thyroid-stimulating hormone (TSH). Your pituitary gland then releases TSH — the amount depends on how much thyroxine and triiodothyronine are in your blood. Finally, your thyroid gland regulates its production of hormones based on the amount of TSH it receives.
Although this process usually works well, the thyroid sometimes fails to produce enough hormones. This may be due to a number of different factors, including:
Less often, hypothyroidism may result from one of the following:
Although anyone can develop hypothyroidism, it occurs mainly in women older than 40, and the risk of developing the disorder increases with age. You also have an increased risk if you:
When to seek medical advice
See your doctor if you're feeling tired for no reason or have any of the other symptoms of hypothyroidism, such as dry skin, a pale, puffy face, constipation or a hoarse voice.
You'll also need to see your doctor for periodic testing of your thyroid function if you've had previous thyroid surgery, treatment with radioactive iodine or anti-thyroid medications, or radiation therapy to your head, neck or upper chest.
If you have high blood cholesterol, talk to your doctor about whether hypothyroidism may be a cause. And if you're receiving hormone therapy for hypothyroidism, schedule follow-up visits as often as your doctor recommends. Initially, it's important to make sure you're receiving the correct dose of medicine. And over time, the dose you need to keep your thyroid functioning normally may change.
To learn about ways to cure this condition continue reading.