Q: Based on some articles I’ve read recently, I am almost certain I have an underactive thyroid. My doctor ran a test, but it came back normal. Are there tests he might be missing?
Dr. Wright: The symptoms of an underactive thyroid (also known as hypothyroidism) include weight gain, fatigue, constipation, depression, sore muscles, and extreme sensitivity to cold temperatures. But since these symptoms are ones that are relatively common and can indicate many other problems in the body, doctors now rely heavily on laboratory tests to officially diagnose cases of hypothyroidism.
These thyroid function tests usually measure thyroid stimulating hormone (TSH, produced by the pituitary gland) and thyroid hormone output (T3 and T4). But since thyroid hormones regulate many key functions of the body, levels in the blood do not always reflect what is going on in the tissues.
If you and your doctor have ruled out other potential causes of the symptoms you’ve been experiencing, ask him or her to measure your basal metabolic rate (BMR), which can better help assess thyroid function.