There are too many possible causes of fatigue to offer a one-size-fits-all solution. Anemia due to inadequate iron or lack of B vitamins can make people feel worn out. So can many serious health problems such as chronic infection, problems with kidneys or liver, certain types of cancer and heart failure. One common problem that can make a person feel tired all the time is low thyroid function or hypothyroidism. In addition to fatigue, too little thyroid activity can lead to apathy, depression, weakness and other symptoms. Doctors usually treat this problem with a daily dose of synthetic thyroid hormone, but sometimes patients don’t feel quite well despite taking the medicine. What else might they do?
Reader Hates Feeling Tired All the Time:
Q. I had thyroid cancer, so my thyroid gland was removed. I’ve been on Synthroid ever since then, despite telling my endocrinologist that I’m tired all the time. When I wake up, I feel pretty good. Within an hour of taking my Synthroid, I’m ready to go back to sleep.
I’ve asked my doctor for either Armour Thyroid or Nature-Throid, but get nowhere. She is interested only in lab results, not how I feel. Is there any research that might convince her?
Research on T3 and T4:
A. Doctors treating people with underactive thyroid glands (or in your case, no gland at all) generally start by prescribing levothyroxine, also known as T4 because it contains four iodine atoms in the molecule. The physician then monitors the patient’s thyroid-stimulating hormone (TSH, also known as thyrotropin) to make sure it is within the normal range. The brain uses TSH as a messenger to tell the thyroid gland to make more or less hormone; when TSH is in the normal range, it suggests that the brain has determined that the right amount of thyroid hormone is circulating in the bloodstream.
While this works well for many patients, some people don’t find it helpful. They may report that they feel tired all the time–a symptom of low thyroid function–despite TSH tests within the normal range. To understand this, you should know that body tissues don’t use T4 directly. Instead, they use an enzyme to knock one iodine atom off the T4 molecule and convert it to the active thyroid hormone, T3 (aka triiodothyronine).
Trouble Converting T4 to T3:
Research shows that some people do not readily convert T4 (Synthroid or levothyroxine) to the active T3 hormone (Gereben et al, Nature Reviews. Endocrinology, Nov. 2015). Common genetic variations determine the activity of these converting enzymes known as deiodinases. According to recent research, people with genetic variants associated with lower enzyme activity are more likely to suffer from autoimmune diseases affecting the thyroid gland, such as Grave’s disease and Hashimoto’s disease (Inoue et al, Immunological Investigations, July 2018).
Such individuals may feel better when they take T3 with T4, although getting the dose right can be tricky. Our Guide to Thyroid Hormones and our one-hour radio show: Thyroid Mysteries, Controversies and the Latest Research (Show # 1015) may change your doctor’s mind. In the guide, you will also learn about common symptoms of too little or too much thyroid hormone.
