|
|
For other articles and previous issues click here. July 4, 2005 Thyroid
Disease in Women Approximately 20 million Americans have some type of thyroid disorder, but 13 million of those people are unaware of its presence. Despite its common occurrence, thyroid disease often goes undiagnosed because symptoms vary in their presentation and severity and may be attributed to another condition. Women in particular are often left frustrated and without a conclusive diagnosis. Symptoms such as fatigue, weight loss or gain, depression and anxiety, constipation or loose bowels, menstrual irregularities, and decreased libido may be treated individually. Thyroid disease is much more prevalent in women than men—women are five to eight times more likely to develop hypothyroidism and eight to 10 times more likely to develop hyperthyroidism. One in eight American women will develop a thyroid disorder sometime during her lifetime. Older women and women who have recently given birth are at increased risk—more than 15% of women are diagnosed with hypothyroidism by the age of 60 and up to 20% of women develop a postpartum thyroid disorder. Another major concern for women: Thyroid disease can increase the risk of cardiovascular disease, infertility, and osteoporosis. Thyroid Function The pituitary gland controls thyroid hormone production by releasing thyroid-stimulating hormone (also called thyrotropin) into the bloodstream in response to low levels of T-4 and/or T-3, which signals the thyroid to manufacture more hormone. To manufacture thyroid hormone, the thyroid gland requires iodine, which is supplied through various foods, including anything with iodized salt and milk. Outside the United States, dietary iodine deficiency is the primary cause of thyroid disease. The hormone produced by the thyroid gland is essential to cellular function throughout the body, controlling chemical reactions such as cell temperature and growth and affecting every tissue and organ. Because the thyroid plays such an important role in metabolism, thyroid disorders can impact body weight, muscle strength, skin health, memory, heart rate, and the menstrual cycle. Patricia Vasconcellos, RD, CDE, LDN, spokesperson for the American Dietetic Association and outpatient dietitian at Falmouth Hospital, Cape Cod, Mass., says, “The thyroid gland is one of the regulating engines of the body. It sends thyroid hormones into the bloodstream that can affect everything from the heart to skin texture, and it helps control metabolic rate.” Thyroid Disorders Goiter, an enlargement of the thyroid, is the gland’s sensitivity response to either too much or too little iodine and can occur in both hypothyroidism and hyperthyroidism. Most often, thyroid problems result from an autoimmune disorder—when the body’s immune system “attacks” its own tissues. Hypothyroidism, the most common thyroid disorder, is often caused by Hashimoto’s thyroiditis, also called chronic thyroiditis or autoimmune thyroiditis. In this condition, inflammation of the thyroid gland results when antibodies attack the thyroid and decrease its hormone production. This condition is most often diagnosed in women between the ages of 30 and 60. Hyperthyroidism, also more common in women than men, is most often caused by Graves’ disease, another autoimmune disorder that causes an overproduction of thyroid hormone. Graves’ disease is most often diagnosed in women in their 20s and 30s. Plummer’s disease, also called toxic nodular goiter, is a more common cause of hyperthyroidism in women over the age of 60 and is caused by an enlarged thyroid with multiple nodules that produce too much hormone. Treatments and Nutrition “If you have a thyroid disorder, certain foods can help or hinder the thyroid function,” Vasconcellos advises. However, she cautions, “you don’t want to use food to treat the thyroid disorder. It should be complementary to medication.” Certain foods contain compounds called goitrogens that interfere with normal thyroid function or, after they are ingested, interact with other substances in the body to form goitrogens. “Natural goitrogens can suppress the thyroid function,” Vasconcellos explains. Goitrogenic foods include the cruciferous vegetables (broccoli, brussels sprouts, cauliflower, cabbage, rutabagas, turnips, kohlrabi, kale), millet, peaches, peanuts, walnuts, pine nuts, radishes, spinach, and strawberries. The isothiocyanates in these foods reduce thyroid function by interfering with the activity of an enzyme called thyroid peroxidase, which helps normal thyroid function by adding iodine atoms onto thyroid hormones. Soy, a staple in the vegetarian diet, is also a goitrogen and appears to increase T-4 without affecting T-3 levels. Isoflavones in soy, such as isothiocyanate, block the activity of thyroid peroxidase. Ultimately, this impairs thyroid function and can lead to weight gain. Nutritionists and physicians recommend limiting intake of natural goitrogens but not eliminating them, since soy and cruciferous vegetables provide other proven benefits. Women with a thyroid condition should limit soy intake to no more than one daily serving, which is equivalent to 4 ounces of tofu, 2 teaspoons of soy sauce, or 8 ounces of soy milk. Cruciferous vegetables and other foods mentioned above should also be limited to 1 cup two to three times per week. “Greater than 1 cup daily is considered excessive for those with a thyroid condition,” Vasconcellos says. She adds that cooking appears to make the goitrogenic compounds in these foods inactive and recommends that women with thyroid disorders consume goitrogenic foods in cooked form rather than raw. If these goitrogenic foods suppress thyroid function, can women with overactive thyroid glands increase the amounts eaten of these foods? Vasconcellos says no. “Eating goitrogens can actually increase the effects of antithyroid medications taken for hyperthyroidism,” she emphasizes. For women with hyperthyroidism, Vasconcellos recommends the following: • a high-calorie balanced diet; • a higher fluid intake, if not contraindicated (eg, renal disease); • appropriate calcium, vitamin D, and phosphorus supplements for bone health; and • avoidance of stimulants such as caffeine (coffee, tea, cola, and chocolate), which can stimulate thyroid function. Vasconcellos says, “One of the main objectives for women with hypothyroidism is controlling body weight through a calorie-controlled diet appropriate for their age and weight.” In addition to a balanced, calorie-controlled diet, Vasconcellos recommends that women with hypothyroidism limit consumption of natural goitrogens and increase fiber and fluid intake. Increasing fiber (fruits and vegetables) and fluids can help with the constipation often experienced by women with hypothyroidism. In addition to foods, minerals are also important to thyroid function. Some clinical research has suggested that the minerals copper, zinc, and selenium can influence thyroid hormone utilization. Recently, selenium was found to help prevent and manage cardiovascular conditions, as well as support the conversion of T-4 to T-3 thyroid hormone. The daily recommended dose is 1 milligram copper, 25 milligrams zinc, and 100 micrograms selenium—amounts that are in many daily multivitamins. Other lifestyle modifications can aid women in alleviating symptoms associated with thyroid disorders. Although smoking is an unhealthy habit for anyone, women with a thyroid disorder should not smoke because nicotine has been shown to adversely affect the conversion of T-4 to T-3. Regular exercise, including appropriate cardiovascular conditioning and strength exercises, can assist a sluggish metabolism in hypothyroidism and help prevent osteoporosis, which frequently afflicts women with hyperthyroidism. Pregnancy and Thyroid In many women, postpartum thyroiditis initially appears as hyperthyroidism for two to three months, followed by a hypothyroid phase for up to nine more months. While the majority of women fully recover from postpartum thyroiditis, approximately 10% of women will have permanent hypothyroidism. Pregnant women with preexisting thyroid conditions, such as Hashimoto’s thyroiditis and Graves’ disease, are at higher risk for developing postpartum thyroiditis, and the condition may recur following subsequent pregnancies. The American Thyroid Association (ATA) recommends that women already diagnosed with hypothyroidism undergo additional testing during pregnancy to check whether they may require an increase in their thyroid hormone medication. The ATA also advises pregnant women to be sure that prenatal vitamins contain iodine. Pregnant and lactating women need 220 to 290 micrograms of iodine daily compared with the 150 micrograms required by other adults. “It’s important for pregnant women to correct any imbalances that may be due to inadequate intake of iodine,” Vasconcellos notes. Research Researchers noted that because the fetus depends entirely on its mother for thyroid hormone during the first four to five months of gestation, thyroxine is especially important for fetal brain and neural development. Pregnant women with underactive thyroids or who do not get an adequate supply of iodine are at risk of having children with lower IQs and learning problems, such as attention-deficit/hyperactivity disorder. Maternal hypothyroidism increases the risk of pregnancy complications, such as miscarriage, gestational hypertension, and preeclampsia. In addition, premature birth, the most common cause of neuropsychological dysfunction in children, occurs more frequently in women with asymptomatic hypothyroidism. Research presented at the ATA/AACE symposium indicates that 100,000 or more women may have asymptomatic hypothyroidism that can also affect childbirth and later child development. As of May 2004, preconception and early pregnancy thyroid testing was under vigorous debate in the medical community as a result of clinical studies linking lowered IQ in children born to mothers with untreated hypothyroidism during pregnancy and asymptomatic hypothyroidism with a higher risk of premature birth. Testing all women who become pregnant each year—approximately 4 million—would be expensive and is not yet supported by evidence. The ATA, along with many endocrinologists, support testing women at high risk for thyroid disease who are planning to conceive or are in the early stages of pregnancy. At-risk women would include those with family members who have thyroid disease and those with a history of thyroid problems or other autoimmune disorders, such as type 1 diabetes, lupus, or rheumatoid arthritis. Ongoing studies will help clarify the issue of preconception and early-pregnancy thyroid testing. British researchers have begun testing more than 20,000 pregnant women to determine whether asymptomatic hypothyroidism affects brain function in their children. While those results will take years, evaluating the effects of asymptomatic hypothyroidism on premature delivery will be completed more rapidly. The ATA has proposed an action plan that calls for government institutions (eg, the Centers for Disease Control and Prevention), professional organizations such as the ATA and the AACE, and nongovernment groups such as the March of Dimes to coordinate and implement improved patient education, clinical practice review, and clinical research on maternal hypothyroidism and its impact on pregnancy and fetal/child development. — Jennifer Sisk, MA, is a certified wellness educator/consultant with the American College of Wellness and a certified fitness instructor with the Aerobics and Fitness Association of America. She currently teaches in suburban Philadelphia. Resources Doerge DR, Sheehan DM. Goitrogenic and estrogenic activity of soy isoflavones. Environ Health Perspect. 2002;110(suppl3):349-353. National Women’s Health Information Center Web site: www.4woman.gov Rosenthal MS. The Thyroid Sourcebook. 3rd ed. Los Angeles: Lowell House; 1998:270. Shames RL, Shames KH. Thyroid Power: 10 Steps to Total Health. New York: HarperResource; 2001:314. |
 |
 |