Serum pituitary and steroid hormone levels in the adult male: one value is as good as the mean of three.

The result of the hormone concentration of one blood sample was used to determine the accuracy of predicting not only the hormone concentrations of a second and third sample drawn 15 minutes apart, but also the mean value of the three samples. Three blood specimens from 73 men involved in two previously reported studies (A and B) were assayed individually for luteinizing hormone, follicle-stimulating hormone, prolactin, testosterone, androstenedione, dehydroepiandrosterone sulfate, estradiol, and cortisol. The predictive correlation of one single hormone value, when compared with the mean of three values, was 0.90 or greater, except for prolactin in study A (0.86) and testosterone in study B (0.86). Since the hormone level obtained for one sample has such a high predictive value for the hormone levels of the other two samples, drawing more than one sample is redundant.