Thyroid glandThe                       thyroid gland , a part of the endocrine (hormone ) system, plays a major role in regulating the body's metabolism.

Endocrine glands The endocrine system is the chemical control center of the body. The pituitary gland is often considered the master control; sending out hormones that regulate the function of the thyroid, adrenal glands, ovaries, and testis. Over- or under-production of hormones from any of these glands is associated with many different types of disease.

Hypothyroidism

[Alternative Names]  [Definition]  [Causes, Incidence and Risk Factors]  [Symptoms]  [Signs And Tests]  [Treatment]  [Expectations (Prognosis)]  [Complications]  [Calling Your Health Care Provider]  [Prevention] 

Alternative Names

adult hypothyroidism; myxedema

Definition

A condition of decreased activity of the thyroid gland. See also hypothyroidism; primary and hypothyroidism; secondary.

Causes, Incidence and Risk Factors

The thyroid gland is located in the front of the neck just below the larynx. The thyroid gland secretes several hormones which control body metabolism and regulate calcium balance. These hormones are thyroxine (T4), triiodothyronine (T3), and calcitonin.
The secretion of T3 and T4 by the thyroid is controlled by an endocrine feedback system involving the pituitary gland and the hypothalamus in the brain. Calcitonin is regulated by the amount of calcium in the blood and acts in conjunction with the parathyroid gland to control calcium levels. Since the thyroid gland is regulated by the pituitary gland and the hypothalamus, thyroid disorders may result not only from defects in the gland itself, but also from disruption of the control system. Thyroid disorders caused by overproduction of thyroid hormones are called hyperthyroidism, and underproduction of these hormones is known as hypothyroidism.
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, with the most severe form called myxedema, which is a medical emergency.
The causes may be due to disease of the thyroid gland (primary hypothyroidism) such as Hashimoto's disease where the body's immune system attacks the thyroid gland, or from failure of the pituitary gland to secrete a hormone to stimulate the thyroid gland (secondary hypothyroidism). Other causes are congenital defects, surgical removal of the thyroid gland, irradiation of the gland, or inflammatory conditions. Risk factors include being over 50 years old, being female, obesity, thyroid surgery, and x-ray or radiation treatments. The incidence is 2 out of 100 people.

Symptoms

Early symptoms:

• weakness
• fatigue
• cold intolerance
• constipation
• weight gain (unintentional)
• depression
• joint or muscle pain
• thin, brittle fingernails
• thinning of hair
• pale color

Late symptoms:

• slow speech
• dry flaky skin
• thickening of the skin
• puffy face, hands and feet
• decreased taste and smell
• thinning of eyebrows
• hoarseness
• menstrual periods, abnormal

Additional symptoms that may be associated with this disease:

• tongue problems
• swelling, overall
• skin color, patchy
• nipple discharge, abnormal
• muscle spasms (cramps)
• muscle pain
• muscle atrophy
• movement, uncoordinated
• menstruation, absent
• joint stiffness
• hearing loss
• hair, dry
• hair loss
• facial swelling
• ear noise/buzzing
• drowsiness
• breast development in males
• blood pressure, high
• appetite, loss
• ankle, feet, and leg swelling
• short stature
• sutures - separated
• teeth - delayed or absent formation

Signs And Tests

A physical examination reveals delayed muscle reflexes. Vital signs (temperature, pulse, rate of breathing, blood pressure) reveal slow heart rate, low blood pressure, and low temperature.
A chest X-ray may reveal an enlarged heart.
Laboratory tests to determine thyroid function include:

• T4 test
• T3 resin uptake
• serum TSH

Additional laboratory abnormalities may include:

• increased cholesterol levels
• increased liver enzymes
• increased serum prolactin
• low serum sodium
• low blood glucose
• a CBC that shows anemia

This disease may also alter the results of the following tests:

• uric acid
• triglycerides
• T3
• sodium, urine
• Schilling test
• radioactive iodine uptake
• glucose test
• antithyroglobulin antibody

Treatment

The purpose of treatment is to replace the deficient thyroid hormone. Levothyroxine is the most commonly used medication, but others are available. The lowest dose effective in relieving symptoms is used. Life-long therapy is indicated as relapses will occur if therapy is interrupted. Medication must be continued even when symptoms subside.
After replacement therapy has begun, report any symptoms of increased thyroid activity (hyperthyroidism) such as restlessness, rapid weight loss, and sweating.
A high-fiber, low-calorie diet, and moderate activity help relieve constipation and promote weight loss.
Myxedema coma is treated by intravenous thyroid replacement and steroid therapy. Supportive therapy of oxygen, assisted ventilation, fluid replacement, and intensive-care nursing may be indicated.

Expectations (Prognosis)

With early treatment, return to the normal state is usual. However, relapses will occur if the medication is not continued. Myxedema coma can result in death.

Complications

Myxedema coma, the most severe form of hypothyroidism, is rare. It may be caused by an infection, illness, exposure to cold, or certain medications. Symptoms and signs of myxedema coma include unresponsiveness, decreased breathing, low blood pressure, low blood sugar, and below normal temperature.
Other complications are heart disease, increased risk of infection, infertility, miscarriage in pregnant women, and pituitary tumors.

Calling Your Health Care Provider

Call your health care provider if signs of hypothyroidism (or myxedema) are present.
Call your health care provider if chest pain or rapid heart beat occur, infection occurs, symptoms worsen or do not improve with treatment, or new symptoms develop.

Prevention

There is no prevention for hypothyroidism; however, screening tests in newborns can detect congenital hypothyroidism.