BASAL PROLACTIN AND TOTAL LACTOGENIC HORMONE LEVELS BY MICROBIOASSAY AND IMMUNOASSAY IN NORMAL HUMAN SERA

The availability of an improved microbioassay for prolactin measuremen t has enabled comparison of lactogenic hormone bioactivity and immunoa ctivity in normal human serum. Serum was studied from 61 normal female s and 15 normal males. The correlation of both assays was very close f or all subjects with a mean ratio of bioassay to immunoassay of 1.5 (r ange 0.8-2.0) for prolactin and 1.4 (range 0.5-1.9) for total lactogen ic hormone. There was no significant variation in prolactin or total l actogenic hormone values by microbioassay or immunoassay with sexual o r menstrual status. Postmenopausal prolactin levels were lower by both assays compared with premenopausal values with a relative and absolut e decrease in prolactin bioactivity with age. These findings indicate that there is a good correlation between prolactin bioactivity and imm unoactivity in human serum.