Subtle signs of a thyroid disorder
Problems with estrogen and testosterone, the body’s main sex hormones, tend to attract widespread public interest. But we might all be better off paying more attention to a far more common endocrine disorder: abnormal levels of thyroid hormone. Thyroid disorders can affect a wide range of bodily functions and cause an array of confusing and often misdiagnosed symptoms.
Because the thyroid, a small gland in the neck behind the larynx, regulates energy production and metabolism throughout the body, including the heart, brain, skin, bowels and body temperature, too much or too little of its hormones can have a major impact on health and well-being.
Yet in a significant number of people with thyroid deficiencies, routine blood tests fail to detect insufficient thyroid hormone, leaving patients without an accurate explanation for their symptoms. These can include excessive fatigue, depression, hair loss, unexplained weight gain, constipation, sleep problems, mental fogginess and anxiety. Women of childbearing age may have difficulty getting pregnant or staying pregnant.
Although thyroid disorders are more common in adults, children, whose cognitive and physical development depend on normal thyroid function, are not necessarily spared. In a review article published last year in JAMA Pediatrics, doctors from the Children’s Hospital of Philadelphia pressed primary care doctors to recognize childhood thyroid disease and begin treatment as early as the second week of life to ensure normal development.
Symptoms of thyroid dysfunction vary widely from person to person and tend to develop gradually, so patients and doctors may not recognize them as a problem warranting exploration and treatment.
Hypothyroidism — low hormone levels — in particular is often misdiagnosed, its symptoms resembling those of other diseases or mistaken for “normal” effects of aging. Indeed, the risk of hypothyroidism rises with age. Twenty percent of people older than 75, most of them women, lack sufficient levels of thyroid hormone that, among other problems, can cause symptoms of confusion commonly mistaken for dementia.
Symptoms of an overactive thyroid, or hyperthyroidism, include weight loss, increased appetite, anxiety, insomnia and heart palpitations, including atrial fibrillation, a risk factor for stroke. Yet, as with too little thyroid hormone, older people may lack obvious symptoms and remain undiagnosed.
Overproduction or underproduction of thyroid hormone afflicts as many as 20 million Americans, including a disproportionate number of women and the elderly. An estimated 1 woman in 5 ages 60 and older has some form of thyroid disease.
According to Dr. Jeffrey Mechanick, an endocrinologist affiliated with the Icahn School of Medicine at Mount Sinai in New York, “Unfortunately, older adults experience fewer of the typical signs and symptoms associated with thyroid disorder. This can make diagnosis difficult.”
Complete tests for thyroid function include three measurements: for the hormones thyroxine (T4) and triiodothyronine (T3) produced by the thyroid itself, and for thyroid-stimulating hormone (TSH, also called thyrotropin) produced by the pituitary gland to regulate the thyroid. Production of thyroid hormones requires iodine in the diet, found in high amounts in iodized salt, eggs, sea vegetables like kelp, fish and shellfish from ocean waters and unpasteurized dairy products.
Even when blood levels of thyroid hormone are normal, if the level of thyroidstimulating hormone is low (subclinical hyperthyroidism), serious problems can result. In a Swiss study of 70,298 men and women followed for a decade, among the 2,219 who had subclinical hyperthyroidism, the risk of fractures — especially hip fractures — was significantly elevated.
Likewise, subclinical hypothyroidism (normal levels of thyroid hormone but too much thyroid-stimulating hormone) may raise the risk of heart problems, especially in young and middle-aged adults. Treatment of this condition with the drug levothyroxine may reduce this risk, according to a British study.
Although the U.S. Preventive Services Task Force has not yet found sufficient evidence to recommend routine thyroid screening of people without obvious symptoms, the American Association of Clinical Endocrinologists believes thyroid levels should be routinely measured in older people, especially women. And the American Thyroid Association recommends screening adults for TSH starting at age 35 and repeating the test every five years.
Experts believe that between 40 percent and 60 percent of people with thyroid disease do not know they have it. Yet, even for subclinical disorders, proper diagnosis and relatively simple treatment of abnormal thyroid levels can result in a much improved quality of life.
People found to have low levels of thyroid hormone can be easily treated with a daily pill of synthetic hormone, levothyroxine (marketed under such names as Synthroid and Levoxyl), starting with a low dose and gradually increasing (or decreasing) the amount as indicated by careful monitoring. Patients often experience diminished symptoms after about two weeks of hormone treatment.
However, diagnosing subclinical hypothyroidism can be tricky. Dr. Robin P. Peeters of Erasmus Medical Center in the Netherlands recently noted in The New England Journal of Medicine that about 75 percent of patients with this condition have test results that suggest only mild thyroid failure, which doctors may not consider serious.