Premenstrual Syndromes : PMS and PMDD - Rutuja :: The site ...

66 THE PREMENSTRUAL SYNDROMES
Anterior
pituitary
hormones
Ovarian
hormones
Ovary
FSH
Estradiol
Recruitment
Selection
Uterine
Endometrium
Follicle
Dominance
2 4 6 8 10 12 14 16 18 20 22 24 26 28 2
Day of cycle
In its phase of peak steroidogenic activity, the corpus
luteum appears as a swollen vascular area on the
surface of the ovary. When surgically incised, the center
appears yellowish orange due to the high concentration
of cholesterol, which forms the substrate for steroidogenesis.
In conception cycles, the embryo migrates at the
morula stage into the endometrial cavity about 4 days
after ovulation. The following day, the embryo sheds
its zona pellucida and develops a loose adherence to the
endometrium. Implantation in the human can only
occur during a 6–10 day ‘window of implantation’ and
if this happens the hCG from the early pregnancy with
its biological similarity to LH can maintain the activity
of the corpus luteum until approximately 7–8 weeks
from the last menstrual period when placental steroidogenesis
takes over. 26,27 (Figure 8.3 25 ).
When pregnancy does not ensue, a new cohort of follicles
is recruited and the former corpus luteum involutes
slowly over several months. Grossly, the old corpus
luteum has the appearance of an inactive whitish area
of scar tissue known as the corpus albicans.
TESTOSTERONE LEVELS
The physiological roles of androgens in women remain
poorly understood. About 50% of testosterone and
androstenedione come from the ovary, with the
remainder originating in the adrenal gland.
LH
Ovulation
Progesterone
Corpus luteum
Corpus
albicans
Recruitment
Figure 8.2 The changing
levels of pituitary and ovarian
hormones throughout the
human menstrual cycle. FSH,
follicle-stimulating hormone;
LH, luteinizing hormone.
(Reproduced with permission
from Parrish. 21 )
Data on total and free testosterone levels throughout
the normal menstrual cycle are limited due to challenges
with conducting assays at the low levels normally
found in women. 28 In a recent study using very
sensitive detection methods, androgen levels were monitored
on a daily basis throughout a complete menstrual
cycle in 34 healthy women between the ages of 25 and
40 years old (Figure 8.4). Serum testosterone levels
increased gradually, from 1.04 � 0.76 nmol/L in the
menstrual phase to 1.52 � 1.03 nmol/L at 3 days
before the LH surge. Total testosterone levels fell slightly
to 1.1 nmol/L in the midluteal phase. Free testosterone
levels mirrored those of total testosterone in the follicular
phase, but were maintained without the modest
midluteal decline seen with total testosterone. Mean
testosterone levels during the follicular and luteal
phases were not significantly different (1.21 � 1.21 vs
1.18 � 1.21). 29
Serial measurements of testosterone and free testosterone
across the menstrual cycle between women with
prospectively defined PMS and controls revealed no
significant differences. 30
ENDOMETRIAL CHANGES DURING THE
MENSTRUAL CYCLE
Under the influence of rising levels of estradiol, the
endometrium shows extensive glandular mitotic activity
as stromal and glandular tissues proliferate in the