TSH or Thyroid Stimulating Hormone is secreted by the pituitary gland in response to the levels of thyroid hormones circulating in the body. If the amount of thyroid hormone (T4 and T3) are too low, TSH will go up to stimulate the thyroid gland to produce more hormone. (Hypothyroidism 101)
Therefore, when TSH goes up--it means that the thyroid is under-functioning and needs more stimulation to produce thyroid hormone. TSH is one main way to diagnose hypothyroidism or low thyroid gland function.
What is considered normal TSH? Normal TSH values are stated on the lab report, each lab has a different range depending on the type of test they use, as well as the "normal" population they measured from. Typically, normal TSH is between 0.4 to 4.5 or 5.5. The higher the TSH, the worse performing the thyroid gland is (therefore, you generally want a lower TSH).
However, there is a debate as to what the normal range should be.
When I was in naturopathic medical school in 2003, the upper limit of normal range was as high as 10.5. Currently, the upper limit of normal TSH is 4.5 or 5.5 (depending on the lab). Some scientists think that normal TSH values should be lower than they currently are. A number typically quoted is an upper limit of 2.5. This is because 95% of the population has TSH levels that are between 0.4 and 2.5. I have had obstetricians and pre-natal clinicians send their patients to me with TSH levels of 4.2 recommending that I start them on thyroid hormone to bring their TSH levels down to 2.5 or below (hypothyroidism during pregnancy can lead to mental retardation).
What number do I use in clinical practice?
I do not adhere to a black and white diagnosis of hypothyroidism based on TSH values only. The decision of whether or not to treat someone with thyroid hormone should be done on a case to case basis. If I have a patient who has a TSH of 4.2, and who has symptoms of fatigue, difficulty thinking, weight gain and feeling cold all the time, or has fertility issues, or has with positive antibodies and with no other good medical explanation of those symptoms--I would seriously consider a trial of thyroid hormone. (Which thyroid hormone to use?) This is very reasonable in my opinion. On the otherhand, if somebody has a TSH of 4.2 but does not have any symptoms, I probably will not treat because you expose someone to the risks of taking a medication with no clear benefit you are working towards.
2 comments:
Bovine thyroid supplements work faster compared to levo. At the end of the day you will be glad as a healthy thyroid will put the spring back into you life.
I feel best with lower TSH levels, but without therapy they fall in the high normal range. I wonder what percentage of older, fat women on disability payments due to depression actually would be functioning well if they received thyroid supplementation. In other words, are we keeping people on heavy psychotropic medication, at huge social and financial cost, when revising the thresholds for thyroid treatment would get them back into life, happiness and work?
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