Free and protein-bound progesterone during normal and luteal phase defective cycles.
OBJECTIVE
New methods for the measurement of the percent free (%FreeP) and percent corticosteroid binding globulin-bound (%CBG-B) fractions of plasma progesterone (P) are described.


METHODS
Modifications of previously reported equilibrium dialysis and charcoal adsorption assays were used. P binding was analyzed in single midluteal samples of 16 infertile women with endometrial biopsy proven luteal phase defect (LPD) and 10 infertile women with a normal luteal phase.


RESULTS
%FreeP, %CBG-B, percent nonspecific protein-bound P (%NSP), total P and total plasma estradiol (E2) were measured during the normal ovulatory cycles of 5 women. The mean follicular phase %FreeP was found to be lower than in the luteal phase due to a decline in the late follicular phase. This decline correlated with the preovulatory rise in E2. The mean absolute concentration of free P (FreeP) rose significantly in the luteal phase, positively correlating with total P in both phases. Mean %CBG-B and %NSP were unchanged throughout the cycle. P was lower in LPD vs. normal cycles, but %FreeP and %CBG-B were not different. E2 highly correlated with P but not with %FreeP and %CBG-B.


CONCLUSIONS
In normal cycles a small but significant decrease in %FreeP occurs in the late follicular phase and is associated with increasing E2. Changes in total P during the ovulatory cycle reflect changes in the concentration of bioactive P. There were no data to support an association of LPD with changes in the bioactive fraction of P.
Minassian
S S
SS
Department of Obstetrics and Gynecology, Jefferson Medical College, Philadelphia, Pennsylvania.
Wu
C H
CH
D000328:Adult; D001774:Blood Chemical Analysis / Q000379:methods; D005260:Female; D005498:Follicular Phase / Q000097:blood; D006801:Humans; D007247:Infertility, Female / Q000097:blood* / Q000503:physiopathology; D008137:Longitudinal Studies; D008183:Luteal Phase / Q000097:blood* / Q000502:physiology; D011374:Progesterone / Q000097:blood*; D011376:Progesterone-Binding Globulin / Q000032:analysis*; D014156:Transcortin / Q000032:analysis
D011376:Progesterone-Binding Globulin; D011374:Progesterone; D014156:Transcortin