7720-3850 is specific for 17-Alpha-Hydroxyprogesterone, a steroid hormone produced by the adrenal gland and gonads. It is derived from progesterone and production is increased in the third trimester of pregnancy. 7720-3850 shows the following reactivity in ELISA: 17-OH-Progesterone 100% Progesterone 10% Deoxycorticosterone 1-5%