TSH stands for thyroid stimulating hormone and it is measured through a blood test to determine thyroid function. If your doctor suspects that you may be suffering from thyroid disease, a measurement of your TSH levels will be taken. Related lab tests also are likely to be ordered that measure your T4 and T3 hormone levels. T4 and T3 are the thyroxine and triiodothyronine hormones respectively, and both are produced by the thyroid gland.
If your doctor suspects that you may be suffering from thyroid disease, he will want to see if your TSH is low. TSH blood tests are ordered on newborns who may have an underactive thyroid gland, patients on thyroid replacement therapies and people with symptoms of thyroid disease. Thyroid disease symptoms include increased heart rate, sudden weight loss, hyperactivity and difficulty sleeping.
A low TSH level with a normal T4 and T3 result indicate that the person suffers from a mild form of hyperthyroidism. Hyperthyroidism occurs when a person has an overactive thyroid gland and produces too much of the thyroid hormone thyroxine. Low TSH and high T4 and T3 levels indicate a more severe form of hyperthyroidism. If all three levels are low, it indicates that the person suffers from a non-thyroid illness. In rare cases, it can indicate a person has a problem affecting their pituitary gland, such as trauma to the area or cancer.
If you have a low TSH, your doctor will monitor your levels on a regular basis to make sure you retain normal thyroid function. If you are put on thyroid medication to control the levels, repeat blood tests are typically ordered every few months. After you have stabilized on the medication, a physician only may need to look at your TSH levels every six months to a year.
Screening for Low TSH Levels
If you are a healthy adult over the age of 35 with no suspected hyperthyroidism, your doctor will still likely order a screening of your TSH levels. Many physicians screen for thyroid disease by measuring TSH levels every five years. More frequent routine screenings are done for higher risk patients like pregnant women.
Certain medications, like thyroid replacement hormones and aspirin can affect the accuracy of your TSH levels. Make sure you let him know all over the counter and prescription medications you may be using. He may ask you to stop certain substances prior to the blood test. Stress and pregnancy are also known to have an effect on TSH levels.