A specific 125I radioimmunoassay method for progesterone

A specific and sensitive radioimmunoassay method for progesterone and its application to clinical practice are described. Antiserum of progesterone was prepared in rabbits by repeated subcutaneous injections of 11 alpha-hydroxyprogesterone-bovine serum albumin conjugate emulsified in complete Freund's adjuvant. The antiserum was so specific that the chromatographic purification could be omitted for sample preparation. A conjugate of 11-alpha-hydroxyprogesterone with tyrosine methyl ester was also prepared, and radioiodinated by the chloramine-T method. Immunoreactivity of the labeled progesterone was stable at 40C for up to 40 days. Sensitivity of the assay was 0.05 ng/tube. The intra and inter-assay coefficient variations were 7.0% and 14.4%, respectively. There was a linear correlation (r = 0.95) between the amounts of progesterone added and the values determined by the radioimmunoassay method. The mean recovery rate was 86.4%. Serum progesterone levels in volunteers and infertile patients with histological diagnosis of normal luteal function are statistically higher in mid-luteal phase than any progesterone levels in patients with histological diagnosis of luteal insufficiency. This indicates that any single determination of serum progesterone levels in midluteal phase might be useful in evaluating corpus luteum function. (author)