The thyroid gland is an organ in the neck that produces hormones that regulate important bodily functions, including metabolism. The thyroid is stimulated to produce its hormones by another hormone called thyroid stimulating hormone, or TSH. When thyroid hormone levels are abnormally high, producing a condition known as an overactive thyroid or hyperthyroidism, the TSH level is typically low. Low TSH can cause a host of symptoms, which generally reflect the high thyroid hormone levels. They range from general symptoms to symptoms specific to particular organs.
Fatigue, nervousness, restlessness and weakness are common symptoms of low TSH. Because these symptoms can be felt with a variety of other conditions, they may not be attributed to low TSH initially. Muscle cramps and tremors may also occur. People with low TSH are often unusually sensitive to the heat and have difficulty tolerating warm weather. A warm summer day for most people may be unbearably hot for them. People with low TSH may also sweat more than others.
Heart and Lungs
People with low TSH often notice their heart pounding hard. They may also feel as if their heart is skipping beats or beating very quickly. An abnormal, irregular heart rhythm called atrial fibrillation may occur when TSH is low. The blood pressure, especially the upper number known as the systolic pressure, may also be elevated. Sometimes the hormone abnormalities related to low TSH have such a negative effect on the heart that they lead to the development of a heart muscle disorder called cardiomyopathy. Heart failure can occur with this condition. Becoming short of breath with normal activities is another common manifestation of low TSH.
The skin may be unusually warm and even have a reddish hue from the increased blood flow that can occur with a low TSH. Skin may become darker or smoother than usual. Hair thinning may be noted. Hives and itching may also occur. The skin of the shins may be affected, appearing raised or darker than usual, and it may resemble the peel of a shrunken orange.
Most people with low TSH have an increased appetite. But they can still lose weight despite eating more than usual because their metabolism is revved up. Unlike most younger adults, senior citizens with low TSH may have a decreased appetite rather than an increased appetite. Some people with low TSH have an enlarged thyroid gland, called a goiter. If the goiter is big enough, it can cause difficulty with swallowing. Having more frequent bowel movements is fairly common, but people with low TSH rarely experience abdominal pain or vomiting.
Personality and Thinking
Some people with a low TSH experience personality changes that run the gamut from depression to losing touch with reality. Confusion, difficulty concentrating and memory problems, including amnesia, may occur. Other potential symptoms include difficulty sleeping, anxiety and irritability.
Call the Doctor
If you experience any symptoms of low TSH, see your doctor, especially if the symptoms last for several weeks or get progressively worse. Blood tests can be performed to measure your TSH and thyroid hormone levels.
Reviewed by: Mary D. Daley, M.D.