Hypothyroidism
Hypothyroidism is a condition in which the thyroid gland fails to produce enough thyroid hormone.
Causes, incidence, and risk factors
The thyroid gland, located in the front of the neck just below the larynx, secretes hormones that control metabolism. These hormones are thyroxine (T4) and triiodothyronine (T3). The secretion of T3 and T4 is controlled by the pituitary gland and the hypothalamus, which is part of the brain. Thyroid disorders may result not only from defects in the thyroid gland itself, but also from abnormalities of the pituitary or hypothalamus. Hypothyroidism, or underactivity of the thyroid gland, may cause a variety of symptoms and may affect all body functions. The body's normal rate of functioning slows, causing mental and physical sluggishness.
The symptoms may vary from mild to severe. The most severe form, called myxedema coma, is a medical emergency. The most common cause of hypothyroidism is Hashimoto's thyroiditis, a disease of the thyroid gland where the body's immune system attacks the gland. Failure of the pituitary gland to secrete a hormone to stimulate the thyroid gland (secondary hypothyroidism) is a less common cause of hypothyroidism. Other causes include congenital (birth) defects, surgical removal of the thyroid gland, irradiation of the gland, or inflammatory conditions. Risk factors include age over 50 years, female gender, obesity, thyroid surgery, and exposure of the neck to X-ray or radiation treatments.
Symptoms
Early symptoms:
- Weakness
- Fatigue
- Cold intolerance
- Constipation
- Weight gain (unintentional)
- Depression
- Joint or muscle pain
- Thin, brittle fingernails
- Thin and brittle hair
- Paleness
- Slow speech
- Dry flaky skin
- Thickening of the skin
- Puffy face, hands and feet
- Decreased taste and smell
- Thinning of eyebrows
- Hoarseness
- Abnormal menstrual periods
- Overall swelling
- Muscle spasms (cramps)
- Muscle pain
- Muscle atrophy
- Uncoordinated movement
- Absent menstruation
- Joint stiffness
- Dry hair
- Hair loss
- Drowsiness
- Appetite loss
- Ankle, feet, and leg swelling
- Short stature
- Separated sutures
- Delayed formation or absence of teeth
The purpose of treatment is to replace the deficient thyroid hormone. Levothyroxine is the most commonly used medication. The lowest dose effective in relieving symptoms and normalizing the TSH is used. Life-long therapy is needed. Medication must be continued even when symptoms subside. Thyroid hormone levels should be monitored yearly after a stable dose of medication is determined. After replacement therapy has begun, report any symptoms of increased thyroid activity (hyperthyroidism) such as restlessness, rapid weight loss, and sweating. Myxedema coma is a medical emergency that occurs when the body's level of thyroid hormones becomes extremely low. It is treated with intravenous thyroid hormones replacement and steroid therapy. Supportive therapy (oxygen, assisted ventilation, fluid replacement) and intensive-care nursing may be indicated.
Credit: National Institute of Health.