*3.2.2. In vitro bioassays*

In vitro bioassays are based on the ability of patients serum to stimulate adenylate cyclase and produce cAMP from cultured hamster ovary cells transfected with human TSHR (CHO-R),23 or rat thyroid cell strain (FRTL-5)24 or human thyroid follicular cells 25 are used as a source for functional TSHR. CHO-R system is slightly more sensitive, and requires an easier culture condition than other systems. Advantages of bioassays are that it gives information about the functional property of TSHR-Ab, but bioassays are more expensive, not widely available, having poor precision and sensitivity of more than 90%. These problems have been solved in newer bioassays.
