Thyroid, Normal but Not Right
By Mary Hartley, RD, MPH
It is not so easy to ameliorate the symptoms of hypothyroidism according to a recent study published in the medical journal, Thyroid. The study found that many patients with Hashimoto's thyroiditis, the most common form of hypothyroidism, continue to have residual symptoms even though their thyroid function tests come back normal from the lab.
A Hypothyroidism Primer
The thyroid is a gland in the neck that secretes hormones that regulate the speed of metabolism. Metabolism is all the chemical reactions that occur in the body to maintain life. The two most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3). T4 and T3 are made by the thyroid as directed by thyroid stimulating hormone (TSH), produced by the pituitary gland. During hypothyroidism, T4 and T3 levels fall while TSH rises as the pituitary pushes the thyroid to produce more hormones.
Hashimoto's thyroiditis is an auto-immune condition that occurs in response to thyroid inflammation. At this point, no one knows what causes it. The symptoms are non-specific and may develop over the course of many years. Doctors are usually prompted to test when a patient reports feelings of chronic tiredness and sluggish, dry hair and skin, depression and forgetfulness, constipation, irritability and nervousness, weight gain, and a hoarse voice. However, not every symptom occurs in every patient, and the symptoms may be due to something else.
To treat hypothyroidism, the doctor prescribes a replacement dose of synthetic T4 and T3 to be taken every day. A low dose is often started and is increased in small increments every four to six weeks until the TSH level returns to normal. Some people experience rapid favorable results with thyroid hormone replacement, but for others, the full effects of treatment may not become apparent for many months – or ever. Once a stable maintenance dose is achieved it usually doesn’t change for years.
Sometimes, a person's TSH level is mildly elevated but the T3 and T4 levels are normal and the patient doesn’t complain of symptoms. That condition is called “subclinical hypothyroidism” and its treatment is controversial. To prevent the risk of bone fractures that comes with overtreatment, doctors often withhold therapy until T4 and T3 levels drop below normal. But when asymptomatic patients have high levels of anti-thyroid antibodies, treatment is often initiated to prevent future thyroid failure. The treatment of subclinical hypothyroidism is individualized at best and frustrating at worst.
Getting It Right
Dr. David S. Cooper, director of the Johns Hopkins Thyroid Clinic in Baltimore told the New York Times, “Roughly 20 percent of people on thyroid replacement therapy receive more hormone than they need.” But also, “20 percent of people on thyroid hormone don’t take enough medication.” However, under-treatment is thought to occur mainly in patients who don’t take their medications regularly.
Still, the authors of the study published in Thyroid acknowledged that some patients continued to report symptoms after thyroid hormone levels returned to normal. They proposed that hypothyroidism might not be the only factor contributing to their symptoms.
The Bottom Line
It would seem wise for patients who struggle on thyroid replacement medications to keep a journal of their symptoms and weight and along with their TSH levels to assist the doctor to make optimal medication adjustments over time.
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