The thyroid gland is a butterfly-shaped structure in the middle of the neck. The gland is responsible for the production of two important hormones - tri-iodothyronine (T3) and thyroxine (T4). These hormones help regulate growth and development, metabolism and body temperature. The function of the thyroid gland is controlled by another hormone, thyroid-stimulating hormone (TSH), which is produced by the pituitary gland.

The American Association of Clinical Endocrinologists estimates 27 million Americans have thyroid disease, characterized by overproduction or underproduction of thyroid hormones. 80 percent of patients are women. Incidence increases with age. The disease is typically classified into one of two categories: hyperthyroidism and hypothyroidism:

Hyperthyroidism

Overproduction of thyroid hormone leads to a condition, called hyperthyroidism. Higher levels of thyroid hormone can speed up many of the processes in the body. Signs can include: feeling overly warm, sweating, weight loss, nervousness or tremor, irritability, increased heart rate, problems with sleep, fatigue, muscle weakness, thinning of the skin, brittle hair, lighter or missed menstrual periods, fertility problems or enlargement of the thyroid gland.

The Hormone Foundation estimates one percent of women have hyperthyroidism. The most common cause is Graves' disease. This condition occurs when the body produces antibodies that cause the thyroid gland to grow and overproduce thyroid hormones. In toxic nodular or multinodular goiter, lumps or nodules form in the thyroid and contribute to an increased production of hormones. Another condition, called thyroiditis, is an inflammation of the thyroid gland.

Hypothyroidism

Underproduction of thyroid hormones is called hypothyroidism. Lower levels of thyroid hormone can slow down many body processes. Patients may feel cold and experience fatigue, memory problems, depression, dry skin, hair loss, constipation, slowed heart rate, mood swings, hoarse voice, heavy menstruation, increased weight, leg cramps and muscle soreness.

Hypothyroidism is the most common class of thyroid problems in the U.S. The Thyroid Foundation of America estimates more than 10 million Americans have the condition. The most frequent cause is Hashimoto's disease, an autoimmune problem in which the immune system attacks the thyroid gland. Hypothyroidism can also be caused by treatment with surgery or radiation therapy for an overactive thyroid gland or disease/damage affecting the pituitary gland. In some cases, a baby with little or no functioning thyroid gland can have hypothyroidism at birth.

Thyroid Disease During Pregnancy

The March of Dimes estimates two percent of pregnant women have some kind of thyroid problem. The most common cause of hyperthyroidism in pregnancy is Graves' disease (affecting 1 in 1,500 pregnant women). For hypothyroidism, the most common cause is Hashimoto's disease.

In the mom, abnormal levels of thyroid hormone (significantly high or low) can trigger anemia, congestive heart failure, pre-eclampsia and pre-term labor. For the baby, the most serious risk is associated with hypothyroidism. Thyroid hormones are critical for brain development. Infants who are born with an underdeveloped or nonfunctioning thyroid gland can be born with severe cognitive, neurological and developmental problems.

Researchers want to find out if treating pregnant women with mild hypothyroidism may have a beneficial effect for the baby. Investigators are looking for women who have subclinical hypothyroidism (i.e., thyroid function is impaired, but patients may have no symptoms or very mild symptoms). Half the women will get treatment (thyroid replacement therapy) and half will get a placebo. Investigators will then follow at the development of the children after birth. Each child will receive an assessment of development and IQ at one year, 18 months, two years, three years and five years.

The trial is called "Thyroid Therapy for Mild Thyroid Deficiency in Pregnancy." Researchers are recruiting patients through the following sites:

University of Alabama, Birmingham, AL

Northwestern University, Chicago, IL

Wayne State University, Detroit, MI

Columbia University, New York, NY

University of North Carolina, Chapel Hill, NC

Case Western University, Cleveland, OH

Ohio State University, Columbus, OH

Oregon Health & Sciences University, Portland, OR

University of Pittsburgh Magee Womens Hospital, Pittsburgh, PA

Brown University, Providence, RI

University of Texas- Southwest, Dallas, TX

University of Texas- Houston, Houston, TX

University of Texas Medical Branch, Galveston, TX

University of Utah Medical Center, Salt Lake City, UT

For more information, log onto:

http://clinicaltrials.gov/ct/show/NCT00388297?order=1

Currently, the US Preventive Services Task Force doesn't recommend routine screening of women for thyroid disease. However, some health experts recommend women who have a family or personal history of thyroid disease or other type of autoimmune disease be screened for the condition.

For more information about the study, log onto:

http://clinicaltrials.gov/ct/show/NCT00388297?order=1

If you have any questions about thyroid disease or your thyroid function, talk with your health care provider. For general information:

American Association of Clinical Endocrinologists, public website

American Thyroid Association

The Hormone Foundation

Thyroid Foundation of America