The thyroid gland, a small butterfly-shaped structure located in the neck, controls a number of metabolic functions through the release of two types of thyroid hormones, thyroxine, or T4, and triiodothyronine, known as T3. Although more T4 is produced by the thyroid, most of it is converted into the more active hormone, T3. Release of thyroid-stimulating hormone, TSH, from the pituitary stimulates the thyroid to produce hormones. Abnormal levels of TSH, T3 or T4 upset the metabolic functions of the body. Around 20 million people, more women than men, suffer from thyroid disease, the Cleveland Clinic states.
Types
When the thyroid produces too much T3 and T4, the body uses up energy faster than normal, a condition known as hyperthyroid. When the thyroid produces too little of the hormones, the body's energy use drops, resulting in a slow metabolism, or hypothyroid. TSH levels often indicate a thyroid imbalance even if T3 and T4 levels are normal, because the amount of TSH is adjusted up or down to compensate for deficiencies or excesses in the thyroid.
Causes
Thyroid disease has many causes. Hypothyroid due to lack of iodine, a necessary substance for thyroid hormone production, affects around 100 million people around the world, the Cleveland Clinic states. Around one in 4,000 newborns has a non-functioning thyroid gland. Inflammation of the thyroid and Hashimoto's thyroiditis, a hereditary autoimmune disorder, also cause hypothyroid. Between 5 and 9 percent of postpartum women experience temporary hypothyroid disease. Removal of cancerous tumors on the thyroid can also result in hypothyroidism.
Hyperthyroid is caused by an overdose of iodine, Grave's disease, an overactive thyroid caused by autoimmune disease, nodules within the thyroid or thyroiditis in postpartum women.
Symptoms
Hypothyroid and hyperthyroid have very different symptoms. Hypothyroid causes weight gain, puffiness in the face, slow speech, dull facial expression and droopy eyelids. Constipation and cold intolerance often develop, along with hair loss, heavy menstrual period, fatigue and slow pulse. Skin becomes thick, dry and scaly. Hyperthyroid causes weight loss (or rarely, weight gain), rapid heartbeat, irritability, sweating, increased appetite and sleep difficulties, as well as scant or absent menstrual periods.
Treatments
Medication to replace low levels of thyroid hormone may be used to treat hypothyroid. Hyperthyroid is treated with medication to slow hormone production or with radiation to destroy the overactive gland. Surgical removal of the gland may also be recommended, followed by medication to replace thyroid hormones.
Complications
Hyperthyroid can cause the eyes to bulge out or become light sensitive, red or swollen. Vision problems can occur. Brittle bones and heart problems can also occur. Thyrotoxic crisis, sudden intensification of symptoms with fever, a racing heartbeat and possibly delirium requires immediate medical attention. Hypothyroid can lead to myxedema coma, severe hypothyroidism characterized by confusion, seizures, coma and heart failure.
