Posted October 1, 2022 by Anusha ‐ 3 min read
Thyroid-stimulating hormone or TSH triggers your thyroid to release its hormones, which mainly impact your body’s metabolism. High TSH levels usually indicate hypothyroidism, and low TSH levels usually indicate hyperthyroidism.
What is thyroid-stimulating hormone (TSH)?
Thyroid-stimulating hormone, commonly called TSH and also referred to as thyrotropin, is a hormone that your pituitary gland releases to trigger your thyroid to produce and release its own hormones thyroxine (T4) and triiodothyronine (T3).
These two hormones are essential for maintaining your body’s metabolic rate the speed at which your body transforms the food you eat into energy and uses it.
Procedure of TSH test
A TSH test involves taking a sample of blood. The blood is typically drawn from a vein that’s inside the inner elbow.
A healthcare provider will perform the following procedure:
First, they’ll clean the area with an antiseptic or other sterilizing solution.
They’ll then tie an elastic band around your arm to make the veins swell with blood.
Once they find a vein, they’ll insert a needle into the vein to draw blood. The blood will be collected in a small tube or vial attached to the needle.
After they draw enough blood, they’ll remove the needle and cover the puncture site with a bandage to stop any bleeding.
What do the results of a thyroid-stimulating hormone test mean?
The normal range of TSH levels is 0.4 to 4.0 milli-international units per liter.
If you’re already being treated for a thyroid disorder, the normal range is 0.5 to 3.0 milli-international units per liter.
A value above the normal range usually indicates that the thyroid is underactive.
This indicates hypothyroidism. When the thyroid isn’t producing enough hormones, the pituitary gland releases more TSH to try to stimulate it.
A value below the normal range means that the thyroid is overactive.
This indicates hyperthyroidism. When the thyroid is producing too many hormones, the pituitary gland releases less TSH.
Normal TSH levels
Normal levels of TSH vary based on your age. In general, normal ranges of TSH for healthy people who aren’t pregnant include:
Infants up to 5 days old: 0.7 – 15.2 micro-international units per milliliter (uIU/mL).
Infants 6 to 90 days old: 0.72 – 11.0 uIU/mL.
Babies 4 to 12 months old: 0.73 – 8.35 uIU/mL.
Children 1 to 6 years old: 0.7 – 5.97 uIU/mL.
Children 7 to 11 years old: 0.6 – 4.84 uIU/mL.
People 12 to 20 years old: 0.51 – 4.3 uIU/mL.
Adults 21 to 99 years old: 0.27 – 4.2 uIU/mL.
Normal TSH levels during pregnancy
First trimester (9 to 12 weeks): 0.18 – 2.99 (uIU/mL).
Second trimester: 0.11 – 3.98 uIU/mL.
Third trimester: 0.48 – 4.71 uIU/mL.
What happens when TSH levels are too high?
If you have too much TSH, it may indicate that your thyroid isn’t making enough thyroid hormone.
This condition is called hypothyroidism, or underactive thyroid.
A number of conditions can cause hypothyroidism, including Hashimoto’s disease.
About 5% of adults in the United States have hypothyroidism.
Since thyroid hormone suppresses TSH release, too little thyroid hormone can cause your pituitary to make excess TSH.
Rarely, issues with your pituitary gland, such as a TSH-secreting pituitary adenoma, or rare genetic conditions can result in higher-than-normal TSH and thyroid hormone levels.
What happens when TSH levels are too low?
If you have too little TSH, it’s most likely that your thyroid gland is making excess thyroid hormone.
This condition is called hyperthyroidism, or overactive thyroid. A variety of conditions lead to hyperthyroidism, including Grave’s disease and thyroid nodules.
A little over 1% of adults in the United States have hyperthyroidism.
Since thyroid hormone suppresses TSH release, high levels of thyroid hormone can cause lower-than-normal TSH levels.
Rarely, issues with your pituitary gland, such as a non-functioning pituitary adenoma, can result in low TSH levels as well as low thyroid hormone levels.