HEK293-PTH1R were plated in white clear bottom 96-well plates at a density of 10,000 cells/well and cultured overnight. At 70-80% confluency, the media was removed and 20 μL of all teriparatide samples added to separate wells before the plate was incubated at 37 °C/5% CO2 for 30 minutes. cAMP levels were then measured with the Promega cAMP Glo Assay according to the manufacturer's instructions. A cAMP calibration curve between 1.9 nM -62.5 μM was prepared separately.