Radioimmunoassay of Plasma 16a-Hydroxyprogesterone

Abstract
This report describes a radioimmunoassay method for the measurement of unconjugated 16a-hydroxyprogesterone (16a-P) in plasma. Utilizing an antiserum against 16a-P combined with a one step celite microcolumn chromatographic system, we have measured this steroid accurately in small a liquors of plasma from both male and female subjects. The mean value ± S.D. for nine adult male subjects was 0.69 ± 0.16 ng/ml. Plasma 16a-P was significantly higher (p <0.01) during the luteal (1.20 ± 0.24 ng/ml) than during the follicular phase (0.57 ± 0.18 ng/ml).