In patients with depression, anxiety and other psychiatric problems, doctors often find abnormal blood levels of thyroid hormone. Treating the problem, they have found, can lead to improvements in mood, memory and cognition.
Now researchers are exploring a somewhat controversial link between minor, or subclinical, thyroid problems and some patients’ psychiatric difficulties. After reviewing the literature on subclinical hypothyroidism and mood, Dr. Russell Joffe, a psychiatrist at the North Shore-Long Island Jewish Health System, and colleagues recently concluded that treating the condition, which affects about 2 percent of Americans, could alleviate some patients’ psychiatric symptoms and might even prevent future cognitive decline.
Patients with psychiatric symptoms, Dr. Joffe said, “tell us that given thyroid hormones, they get better.”
The thyroid, a bow-tie-shaped gland that wraps around the trachea, produces two hormones: thyroxine, or T4, and triiodothyronine, known as T3. These hormones play a role in a surprising range of physical processes, from regulation of body temperature and heartbeat to cognitive functioning.
Any number of things can cause the thyroid to malfunction, including exposure to radiation, too much or too little iodine in the diet, medications like lithium, and autoimmune disease. And the incidence of thyroid disease rises with age. Too much thyroid hormone (hyperthyroidism) speeds the metabolism, causing symptoms like sweating, palpitations, weight loss and anxiety. Too little (hypothyroidism) can cause physical fatigue, weight gain and sluggishness, as well as depression, inability to concentrate and memory problems.
“In the early 20th century, the best descriptions of clinical depression were actually in textbooks on thyroid disease, not psychiatric textbooks,” Dr. Joffe said.
But doctors have long disagreed about the nature of links between psychiatric symptoms and thyroid problems.
“It’s the chicken-and-egg question,” said Jennifer Davis, assistant professor of psychiatry and human behavior at Brown University. “Is there an underlying thyroid problem that causes psychiatric symptoms, or is it the other way around?”
Dr. Davis said it is common for people with thyroid problems to be given a misdiagnosis of psychiatric illness.
Leah Christian, 29, tried antidepressants 10 years ago for depression and anxiety. They did not help. “I just stayed down,” said Ms. Christian, a child care worker in San Francisco.
A few years ago, still struggling, she asked her doctor to refer her to a therapist. The doctor ran a thyroid panel first and found that Ms. Christian had an autoimmune disease called Hashimoto’s thyroiditis, a common cause of hypothyroidism.
Ms. Christian was given levothyroxine, a synthetic thyroid hormone replacement. Her depression and anxiety disappeared, she said: “Turns out, all my symptoms were thyroid-related.”
In a sense, she was lucky; her hormone levels were clearly in the abnormal range. “Normal” levels of thyroid stimulating hormone, or TSH, range from 0.4 to 5. (The higher the TSH level, the less active the thyroid.) Most endocrinologists agree that a score of 10 or over requires treatment for hypothyroidism.
But for people with scores between, say, 4 and 10, things get murkier, especially for those who experience such vague psychiatric symptoms as fatigue, mild depression or just not feeling like themselves.
Some doctors believe these patients should be treated. “If somebody has a mood disorder and subclinical hypothyroidism, that could be significant,” said Dr. Thomas Geracioti, a professor of psychiatry at the University of Cincinnati College of Medicine.
Dr. Geracioti has used thyroid hormones to treat performers with debilitating stage fright; one high-level musician recovered completely, he said.
The idea of treating subclinical hypothyroidism is controversial, especially among endocrinologists. Thyroid hormone treatment can strain the heart and may aggravate osteoporosis in women, noted Dr. Joffe. On the other hand, failing to treat the condition can also stress the heart, and some studies suggest it may increase risk of Alzheimer’s disease and other dementias.
And then there is the misery quotient, which is hard to quantify. “People tend to discount the quality-of-life issues related to residual depression and anxiety,” Dr. Joffe said.
Women are far more likely to develop thyroid problems than men, especially past age 50, and some experts believe that gender accounts for some reluctance to treat subclinical disease. “There’s a terrible bias against women who come in with subtle emotional complaints,” Dr. Davis said. “These complaints tend to be pushed aside or attributed to stress or anxiety.”
Psychiatric symptoms can be vague, subtle and highly individual, noted Dr. James Hennessey, director of clinical endocrinology at Beth Israel Deaconess Medical Center in Boston.
Another complication: It’s not clear to many experts what “normal” thyroid levels really are.
“A patient might have a TSH of 5, which many clinicians would say isn’t high enough to be associated with symptoms,” Dr. Hennessey said. “But if that person’s set point was around 0.5, that 5 would represent a tenfold increase in TSH, which might very well represent disease for that individual.”
In a study published in 2006, researchers in Anhui Province, China, used brain scans to evaluate patients with subclinical hypothyroidism both before and after treatment. They found tangible improvements in both memory and executive function after six months of levothyroxine therapy.
With funds from the National Institutes of Health, Dr. Joffe and researchers at Boston University recently began a trial to tease apart the relationship between subclinical hypothyroidism and certain mood and cognitive symptoms in people over age 60. The results won’t be known for at least a few years. But some clinicians aren’t waiting.