TSH Test (Thyroid-Stimulating Hormone) Popular
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About Our TSH Test (Thyroid-Stimulating Hormone)
Note: Fasting is not required for this test.
Our TSH blood test is used to help determine overall thyroid function by measuring levels of Thyroid Stimulating Hormone. Thyroid-stimulating hormone (TSH) is produced when the hypothalamus releases a substance called thyrotropin-releasing hormone (TRH). TRH then triggers the pituitary gland to release TSH.
- An underactive thyroid is known as hypothyroidism. Hypothyroidism can cause symptoms of weight gain, tiredness, dry skin, constipation, the sensation of being too cold, and/or frequent menstrual periods. Hashimoto's thyroiditis is the most common cause of hypothyroidism.
- An overactive thyroid is known hyperthyroidism. Hyperthyroidism can cause symptoms of weight loss, rapid heart rate, diarrhea, the sensation of feeling too hot, and/or irregular menstrual periods.
Also see our Thyroid Test Panel with TSH.
What does the Thyroid do?
The thyroid is a major player of the endocrine system. It’s a gland located on the front lower part of the neck, right above the Adam’s apple, in front of the voice box or “larynx.” It is responsible for overall maintenance of most bodily functions including metabolism, body temperature, heart rate, mood, and brain activity.
The thyroid maintains all of these functions through the production of two main hormones: thyroxine (T4) and triiodothyronine (T3). Both of these hormones are produced through the thyroid’s use of iodine. T4 and T3 float freely in the blood or bind to transport proteins to be carried to various organs throughout the body.
Since T3 and T4 are responsible for the maintenance of so many systems, it’s easy to see that abnormal levels of these hormones can create far-reaching consequences for the overall functioning of the body and its various systems.
What is TSH and how does it affect the Thyroid?
TSH stands for Thyroid Stimulating Hormone, which is secreted by the pituitary gland. The pituitary gland sensors how much T3 and T4 are in the system. When there is too little T4 and T3, the pituitary gland secretes more TSH in order to stimulate the thyroid into producing more hormones. The same is true for the opposite: When there are too many thyroid hormones in the system, the pituitary gland senses it, then reduces production of TSH until T3 and T4 return to normal levels.
High levels of TSH indicate an underactive thyroid, or hypothyroidism. The levels are higher because TSH is trying to activate more of the thyroid because it’s underactive.
Low levels of TSH indicate an overactive thyroid, or hyperthyroidism. It’s not stimulating the thyroid to continue producing hormones because the thyroid is already producing too much.
What is a normal range of TSH?
Normal ranges for TSH vary slightly by lab and academic association. According to the National health and Nutrition Examination Survey III, normal range for TSH is .45 - 4.120 mIU/lL (milli-international units/Liter). The National Academy of Clinical Biochemists has suggested that a much lower cutoff be 2.5 mIU/L. However, if that were to be adopted as the standard, millions of Americans would be diagnosed with hypothyroidism. In 2012, the American Association of Clinical Endocrinologists and the American Thyroid Association suggested that the typical range be established by the lab, given that it is using a third generation TSH assay. If that’s not available, the next best option would be to use the range of .45 - 4.12 mIU/L. Therefore, most labs go by a range with a limit of 4 mIU/L with a suggestion for “at-risk” with anyone above 2.5 - 3.0 mIU/L. However, few will treat patients with elevated TSH levels, unless the levels are higher than 10 mIU/L.
The range for pregnant women and women going through menopause is on a different scale than those of the average American.
Interpreting results of a TSH test
TSH results are the first indicator of a thyroid problem, but they cannot and should not be the last. Though abnormal TSH levels can indicate that there is a problem, they don’t identify what the problem is, or where the problem is coming from. It’s necessary to run additional thyroid tests to ensure that the problem is the thyroid. These tests would include a total T4 test, T3U test, and T7 or FTI test, to ensure the levels of T3 and T4 in the body match the amount of TSH being secreted. If Thyroid hormone levels are seen to be in an average range, then there may be a problem with the pituitary gland (the creator of TSH). It may be necessary to run tests to ensure that the pituitary gland is working properly.
Who should take the TSH test?
You should take this test if you’re experiencing any of the following symptoms of an underactive thyroid (hypothyroidism) or an overactive thyroid (hyperthyroidism).
- Weight gain
- Dry hair
- Hair loss
- Slow heart rate
- Brain fog
- Memory problems
- Cold intolerance
- Muscle weakness
- Dry skin
- Pain or swelling of the joints
- High cholesterol
- Heavy menstrual cycles
- Increased heart rate
- Weight loss
- Heat intolerance
- Frequent bowel movements
- Increased appetite
- Difficulty Sleeping
- Brittle Hair
In addition to the symptoms described above, you should also get your TSH levels checked if you fall into any of the following categories:
- Woman entering menopause
- Recently gave birth
- Family history of thyroid issues
- Recent surgery
- Family history of pituitary issues
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