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What is TSH 3rd Generation?

If you are looking for information on TSH 3rd generation, then this article is the perfect read...
Tilottama Chatterjee
Last Updated: Apr 3, 2018
TSH: Thyroid Stimulating Hormone
AKA: Thyrotropin
Secreted By: The Pituitary Gland
Main Responsibility: Regulation of the levels of thyroid hormones in the blood
Secreted by the pituitary gland, the thyroid stimulating hormone (TSH) stimulates the thyroid gland (present in the neck) to produce thyroid hormone thyroxine (T4). This T4 is then converted into Triiodothyronine (T3), and is responsible for stimulating metabolism in humans. Any disorder related to the thyroid gland would require a TSH 3rd generation test.
This TSH test is used...
  • ...to diagnose thyroid disorders.
  • ...to check the efficiency and effect of prescribed thyroid medications for those diagnosed with a disorder.
  • ...to diagnose women facing infertility.
  • ...to diagnose and treat newborn kids with congenital hypothyroidism.
Probable Symptoms
A person suffering from excessive secretion of the TSH may become a patient of hypothyroidism or hyperthyroidism. The symptoms of both, listed below, may prompt the doctor to advise for the 3rd generation TSH test.
The symptoms related to hypothyroidism are:
  • Constipation
  • Excessive weight gain
  • Tiredness
  • Increased heart rate
  • Cold intolerance
  • Rapid thoughts
  • Eye irritation, dryness and puffiness around the eyes
  • Depression
  • Hypotonia
  • Menstrual irregularity
The symptoms related to hyperthyroidism include:
  • Anxiousness
  • Weight loss
  • Improper sleep
  • Weakness
  • Muscle aches
  • Intolerance to heat
  • Tremors
  • Vomiting
  • Hair loss
  • Menstrual irregularity
Why the 3rd Generation Test?
According to the first generation TSH assays, the detection limit ranged from 5 to 10 mU/L. The normal range is 0.5 to 5 mU/L. As a result, this test was unable to detect mild hypothyroidism, where the TSH is usually just above 5, and was also useless in case of hyperthyroidism, where the TSH is usually below 0.5.
As for the second generation test, the lower detection limit is about 0.1 mU/L. It is helpful in distinguishing quite accurately between normal and hypothyroid patients. As mentioned earlier, the normal range for TSH is 0.5 to 10 mU/L. Thus, this test is also able to detect hyperthyroid patients from normal individuals, and is widely practiced all round the world.
Coming on to the third generation assays, the TSH ranges between 0.3 to 3.0 (as per the American Association of Clinical Endocrinologists), and the functional sensitivity ranges from 0.01 to 0.02, which allows measurement of TSH at very low concentrations. Also referred to as ultra-sensitive TSH, this test has contributed in improved diagnosis of individuals with thyroid disorders. If the TSH level is below 0.3 mIU/L, it is indicative of hyperthyroidism, whereas a reading that is higher than 3.0 mIU/L indicates hypothyroidism.
Related Tests
The 3rd generation test is done along with the T3 and T4 test.
The T3 test
This test is done to check the functioning of the thyroid. It is related to the action of many different hormones which includes TSH and T4. The T3 test is functional in measuring the triiodothyronine that is attached to proteins or floating free in the blood. During some cases related to hyperthyroidism, it is often seen that T3 may be increased, but T4 may be normal.
The T4 test
The T4 test is used for measuring the blood level of the hormone thyroxine, which is produced by the thyroid gland and helps in controlling the growth and the metabolism of the body. It is done along with the T3 and the TSH tests, for the evaluation of thyroid functioning.
Test Process
In case of adults, a blood sample will be drawn from a vein in the arm. In case of newborns, the blood sample can be drawn by pricking their heels.

Certain medications interfere in the test process and should be stopped before the test is done. Consult your doctor before going for this test, and he would advise whether to carry on or stop with the medications.
Meaning of the Test Result
As per the American Association of Clinical Endocrinologists, TSH ranges between 0.3 to 3.0. When there is a drop in the blood level of thyroid hormone below normal, there is a rise in the TSH level. If there is a high amount of thyroid in the blood, The TSH gets very low.
A high TSH level indicates an underactive thyroid gland, that is unable to act due to a thyroid dysfunction, whereas a very low TSH level means that there is too much thyroid hormone in the blood. Whether high or low, the test result indicates an excess or deficiency in the amount of thyroid hormone available to the body.
Both hyperthyroidism and hypothyroidism can manifest relatively similar symptoms of unexplained fatigue, and weight loss or gain respectively, since the thyroid is closely connected with the metabolic rate. A third generation TSH test is now considered a comprehensive conclusive test for the establishment of either condition.
Disclaimer: This article is for informative purposes only, and does not in any way intend to replace the advise of a medical professional.