Objective: To evaluate the anxiolytic 3 alpha-5 alpha-reduced progeste
rone metabolite allopregnanolone in the luteal phase of the menstrual
cycle in women with premenstrual syndrome (PMS) and controls. Methods:
Thirty-five women with prospectively documented PMS and 36 controls w
ere evaluated. Serum progesterone and allopregnanolone levels were mea
sured on days 19 and 26 of the cycle as determined by urinary LH detec
tion kits. Analysis of variance and Student t tests were used to analy
ze the data. Results: Allopregnanolone levels were significantly lower
on day 26 in the PMS group than in controls (3.6 +/- 0.8 versus 7.5 /- 1.3 ng/mL; P < .04). Significant differences in the ratio of the me
tabolite to progesterone also were noted, with a smaller ratio in the
PMS subjects (0.9 +/- 0.3 versus 3.2 +/- 1.3 ng/mL; P < .05). There we
re no significant differences between the PMS and control groups with
respect to serum progesterone levels. Conclusion: Subjects with PMS ma
nifested lower levels of the anxiolytic metabolite allopregnanolone in
the luteal phase when compared with controls. Diminished concentratio
ns of allopregnanolone in women with PMS may lead to an inability to e
nhance gamma aminobutyric acid-mediated inhibition during states of al
tered central nervous system excitability, such as ovulation or physio
logic or psychological stress. The lowered metabolite levels could con
tribute to the genesis of various mood symptoms of the disorder, such
as anxiety, tension, and depression. (C) 1997 by The American College
of Obstetricians and Gynecologists.