A nonchromatographic radioimmunoassay for 17alpha-hydroxyprogesterone.

A radioimmunoassay is described for the measurement of 17alpha-hydroxyprogesterone in human plasma. We have employed the principle of "immunologic purification." 17-OHP and related steroids are bound to an excess of antiserum. Steroids with a low affinity for the antibody are extracted by ether. The 17-OHP is subsequently freed from antibody by acid hydrolysis and this extract is assayed by radioimmunoassay.