3. What is a 3rd generation TSH and an ultrasensitive TSH?
The original immunoassays for TSH were not sensitive enough to differentiate the very low levels seen in patients with hyperthyroidism from levels seen in normal euthyroid individuals. In the 1980s, more sensitive assays ("second generation") were developed and these were able to identify patients with TSH levels that were suppressed due to the excess amounts of free T4 present in hyperthyroidism. In the 1990s, TSH assays were made even more sensitive and, although these were able to measure even lower levels, they were widely adopted because they performed much better than the second generation assays in the range that was important for differentiating normal from hyperthyroid. Almost all laboratories currently use so-called "third generation" or "ultrasensitive" TSH assays today.
This article was last reviewed on October 15, 2014. | This article was last modified on March 11, 2015.
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