If you need to know which are the TSH reference ranges or you require more information about the role of TSH in the blood you can visit: Normal TSH level in the blood
A TSH (thyroid-stimulating hormone) level in the blood lower than normal range may be a sign of primary hyperthyroidism, a disorder where when the thyroid gland produces too much of the thyroid hormone. For that reason, thyroid hormones T3 (triiodothyronine) and T4 (thyroxine) will be higher than normal.
However, there is a rare situation where the TSH values are low due to a failure of the pituitary gland. In this case, T3 and T4 values will be also lower than normal and it is related to a disorder called secondary hypothyroidism.
TSH (thyroid-stimulating hormone) is also called thyrotropin or thyrotropic hormone.
In the International System of Units (SI), TSH in the blood is measured in mU/L. The numeric values in this case are the same in µUI/ml or in mU/L.
Low TSH blood levels mean:
The TSH level in the blood is a bit low.
If T4 value are in the normal range it is usually due to subclinical hyperthyroidism and no symptom will be present.
The TSH level in the blood is very low, almost non-existent and it may be a sign of suffering from primary hyperthyroidism.
The diagnosis primary hyperthyroidism is conclusive with T4 or T3 hormone levels above the normal range.
The main symptoms of hyperthyroidism are irritability, weight loss, sweating, palpitations or constipation.
You should visit your doctor and he will prescribe you the proper treatment.
Some particular health situation or drugs may reduce your TSH level in the blood:
The following diseases can explain a TSH level in the blood lower than normal:
If the TSH level in the blood is low, the following tips can help you:
You can visit our pages about:
The following values are considered to be above the normal range:
IMPORTANT: These levels are expressed in µUI/ml. They are an example of a healthy man of about 45 years old with no known disease and not taking any medication. The ranges can be different depending on the laboratory or on your personal circumstances.
|Mild TSH decrease|
|0.39 µUI/ml||0.38 µUI/ml||0.37 µUI/ml||0.36 µUI/ml||0.35 µUI/ml||0.34 µUI/ml||0.33 µUI/ml||0.32 µUI/ml|
|0.31 µUI/ml||0.3 µUI/ml||0.29 µUI/ml||0.28 µUI/ml||0.27 µUI/ml||0.26 µUI/ml||0.25 µUI/ml||0.24 µUI/ml|
|0.23 µUI/ml||0.22 µUI/ml||0.21 µUI/ml||0.2 µUI/ml||0.19 µUI/ml||0.18 µUI/ml||0.17 µUI/ml||0.16 µUI/ml|
|0.15 µUI/ml||0.14 µUI/ml||0.13 µUI/ml||0.12 µUI/ml||0.11 µUI/ml||0.1 µUI/ml|
|Marked TSH decrease|
|0.09 µUI/ml||0.08 µUI/ml||0.07 µUI/ml||0.06 µUI/ml||0.05 µUI/ml||0.04 µUI/ml||0.03 µUI/ml||0.02 µUI/ml|
|0.01 µUI/ml||0 µUI/ml|