What is hypothyroidism?
The thyroid gland is a butterfly-shaped organ situated on the front of the neck that secretes two hormones, thyroxine (also known as T4) and triiodothyronine (called T3), that are important in the control of metabolism. Hypothyroidism is a condition in which the thyroid gland does not produce adequate levels of these critical hormones.
Hypothyroidism is very common and is estimated to affect 3% to 5% of the adult population. It is more common in women than in men, and the risk of developing hypothyroidism increases with advancing age.
Hypothyroidism is most commonly a result of an autoimmune condition known as Hashimoto's thyroiditis, in which the body's own immune cells attack and destroy the thyroid gland. Since the activity of the thyroid gland is controlled by other hormones from the pituitary gland and the hypothalamus of the brain, defects in these areas can also cause underactivity of the thyroid gland. Previous surgeries on the thyroid or a history of irradiation to the neck are other causes of hypothyroidism.
Symptoms of hypothyroidism
Symptoms of hypothyroidism can be mild or severe, but are often very subtle. People with a mild form of the condition may not have any symptoms at all. The most serious form of hypothyroidism is called myxedema, which can lead to coma and even death. An underactive thyroid gland affects all organs and functions within the body, leading to both physical and emotional symptoms. Some of the most common symptoms of hypothyroidism in adults are:
- Tiredness and weakness; feeling "run down"
- Weight gain or difficulty losing weight
- Thinning or brittleness of the hair or nails
- Cold intolerance
- Memory loss
- Decreased libido
- Muscle aches and pains
Those affected by more advanced cases of hypothyroidism may notice dryness or thickening of the skin; slow speech; abnormal menstrual cycles; puffiness of the face, hands, or feet; and decreased capacity for taste and smell.
If you are experiencing symptoms of hypothyroidism, your doctor can order simple blood tests to diagnose the condition. An underactive thyroid gland is in most cases easily and completely treated by daily administration of thyroid hormones in tablet form.
Medically reviewed by John A. Seibel, MD; Board Certified Internal Medicine with a subspecialty in Endocrinology & Metabolism