Analysis of progesterone in unextracted serum: a method using danazol [17 alpha-pregn-4-en-20-yno(2, 3-d) isoxazol-17-ol] a blocker of steroid binding to proteins.

A technique has been developed in which progesterone may be measured by radioimmunoassay in unextracted serum. The method depends on the displacement of progesterone from serum binding proteins by danazol, [17 alpha-pregn-4-en-20-yno (2,3-d) isoxazol-17-ol], a compound which also blocks recombination of free progesterone with proteins and does not cross react with the progesterone antiserum. This new method saves time and labour, and fulfills the criteria of sensitivity and precision for clinical use. The results correlate well with those of conventional assays for progesterone.