Could It Be My Thyroid?

When the thyroid isn't working properly it can affect our energy levels, muscle strength, body weight, skin health, menstrual cycle, memory, heart rate and cholesterol levels.

"One might think of the hormone as a pacesetter," says Dr. James Cerletty, Professor of Medicine (Endocrine) at the Medical College of Wisconsin. "Too little and everything slows down. Too much and everything accelerates."

The thyroid, a butterfly-shaped gland that lies across the trachea (windpipe) below the Adam's apple, is controlled by the pituitary, a small gland at the base of the brain that sends out Thyroid Stimulating Hormone (TSH). A healthy thyroid is a little larger than a quarter, and usually can't be felt through the skin. A swollen thyroid - a condition called goiter - can be caused by a lack of iodine in the diet. (Iodine, found primarily in shellfish and iodized salt, is in short supply in some developing countries.) A swollen lobe might look or feel like a lump in the front of the neck.

The thyroid gland produces substances called T3 (triiodothyronine) and T4 (thyroxine), which have identical effects on cells. Together, T3 and T4 constitute thyroid hormone, which affects body functions including heart rate, blood pressure, body temperature and weight.

TSH is a very sensitive indicator of thyroid function, and can be checked by a simple blood test. "The TSH changes 50-fold for every one-fold change in circulating thyroid hormone levels," reports Dr. Cerletty. "When the patient is hypothyroid, TSH is elevated; when hyperthyroid, TSH is suppressed. Fortunately, the TSH test can detect problems early in the evolution of thyroid dysfunction."

The two major types of thyroid disorders are hypothyroidism and hyperthyroidism. Failure to produce adequate amounts of thyroid hormone is termed hypothyroidism. Excessive thyroid hormone production is called hyperthyroidism.

Hypothyroidism
Hypothyroidism is more common in women than in men, and more common in older women than younger women. "About 2% of 20-year-old women have hypothyroidism," Dr. Cerletty reports, "but the incidence in women over the age of 60 is greater than 10%."

The symptoms of hypothyroidism are fairly nonspecific, with fatigue, dry skin and hair, cold intolerance and modest weight gain being most common. Menstrual abnormalities also occur frequently. "Someone once noted that the symptoms are the same ones that occur when we hit the age of forty," says Dr. Cerletty. Less-common signs of hypothyroidism, or underactive thyroid, include:

• Mood swings
• Forgetfulness
• Hoarse voice
• Trouble swallowing
• Increased cholesterol
• Heavy or irregular periods or trouble getting pregnant
• An enlarged thyroid (goiter)

Hypothyroidism often results from Hashimoto's Thyroiditis, an autoimmune disease in which antibodies attack - and sometimes destroy - the thyroid gland. Since the thyroid helps set the body's metabolic rate, people with Hashimoto's don't have enough thyroid hormone for the body to do its work effectively. "There is a hereditary predisposition to this disease," Dr. Cerletty notes. "A patient with a family history of hypothyroidism and symptoms should be tested."

Although some patients with Hashimoto's may have no symptoms, most will experience some degree of fatigue, depression, sensitivity to cold, weight gain, muscle weakness, skin coarsening, dry or brittle hair, constipation, muscle cramps, increased menstrual flow and goiter.

Hypothyroidism is readily treated with Synthroid, an oral tablet of synthetic thyroid hormone.

Patients who have part or all of the thyroid gland removed may briefly experience hypothyroidism until they are stabilized with Synthroid, which mimics the actions of thyroid hormone.

Hyperthyroidism
Hyperthyroidism - an overactive thyroid - is less common than hypothyroidism. The most common cause of hyperthyroidism is Graves disease.

"Symptoms of hyperthyroidism are much more pronounced and specific than those of hypothyroidism," Dr. Cerletty says. "Heat intolerance and weight loss, despite a normal or even increased caloric uptake, are common. The heart rate is increased. Emotional instability is common, often manifest by a 'short fuse.'"

Additional signs of hyperthyroidism include:

• Muscle weakness and tremors
• Irregular menstrual periods
• Sleep disturbances
• Vision problems or eye irritations (Prominent or bulging eyes occur in some patients with Graves disease.)
• Frequent bowel movements
• Enlarged thyroid

Treatments for hyperthyroidism include a medication that interferes with hormone production, destruction of the gland with a radioactive form of iodine, or surgical removal of the overactive thyroid.

Other thyroid disorders
It's important to note that an enlarged thyroid always should be evaluated; the condition might be due to any of several different thyroid disorders.

In addition to hypothyroidism and hyperthyroidism, thyroid nodules also occur quite frequently - in fact, some studies suggest that as many as 4% of adults have them. The nodules should be inspected by ultrasound, a noninvasive test that provides a 3-dimensional look at the thyroid. The current recommendation, according to Dr. Cerletty, is to perform a biopsy of any nodule larger than 1.0 centimeter. "The vast majority of these - some say up to 99% - are benign, not cancerous," he reports. When thyroid cancers do occur they tend to be low-grade, and rarely cause death.

Another fairly common thyroid disorder is Postpartum Thyroiditis. After giving birth, a woman's thyroid can swell or become inflamed. This can cause changing levels of thyroid hormone in the body - either too high or too low - sometimes followed by permanently lowered levels. After 6 months or less, the condition typically goes away with no permanent damage to the thyroid, but for the estimated 25% of the women affected whose thyroid hormones remain low, the disorder can be managed with the synthetic thyroid hormone.

Overall, Dr. Cerletty assures us that even people who have thyroid disorders can maintain their health with appropriate and regular care. "Patients with Graves disease, an enlarged thyroid or thyroid nodules should have an evaluation by an endocrinologist," he says. Those who have ever experienced a thyroid disorder should schedule regular check-ups - including thyroid level tests - with their health care provider.

P.J. Early
HealthLink Contributing Writer

This article includes information from the National Women's Health Information Center, the National Cancer Institute and MedLine Plus.

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.