Simultaneous radioimmunoassay for corticosterone and deoxycortisol in human serum: sex differences in the mean serum concentrations.

A specific radioimmunoassay is described which allows the simultaneous determination of serum corticosterone and deoxycortisol. The method involves extraction with dichloromethane, purification by paper chromatography in a modified Bush-system and quantitation by radioimmunoassay. The normal serum concentration of both steroids were found to be dependent on sex and menstrual cycle. Mean concentrations (+/- S.D.) in males, females (follicular phase) and females (luteal phase) were 4210 +/- 2170 ng/1,2410 + 1480 ng/1 and 4390 +/- 2320 ng/1 for corticosterone and 499 +/- 273 ng/1, 207 +/- 152 ng/1 and 335 +/- 182 ng/1 for deoxycortisol. After adrenal stimulation by corticotropin itself or by insulin induced hypoglycemia, the serum concentrations of corticosterone became significantly higher than those of deoxycortisol. After oral administration of dexamethasone serum concentrations of both steroids were suppressed to levels below the limit of the normal range. One hour after oral metyrapone administration at midnight, serum corticosterone decreased, while serum deoxycortisol increased by a factor of about five. After eight hours serum concentrations of both steroids were increased considerably. Corticosterone attained levels slightly higher than the normal range and deoxycortisol rose to levels which were higher than the normal mean concentrations by a factor of about 500.