Figure. Concentration-dependent activation of PTH1R by PTH. Reporter cells were transfected with either the expression plasmid for par­a­thy­roid hormone 1 receptor (PTH1R) or the mock plasmid and treated with various concentrations of par­a­thy­roid hormone (PTH). Data points shown are the mean ± SEM of an experiment performed in triplicate, and the curve is a fit to Hill equation with an EC50 of 2.2 nM.