Hormonal disorders
Regular interaction of several hormones is important in order for normal ovulation to occur and to prepare the uterine endometrium for future nidation of the embryo.
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A superordinated part of the brain, the hypothalamus, secretes the
GnRH (gonadotropin-releasing hormone). This hormone causes the pituitary
gland (hypophysis) to release the follicle stimulating hormone (FSH)
and the luteinizing hormone (LH) into circulation. It is in this way
that both hormones reach the ovaries. Once there, they trigger the
growth of an ovarian follicle during the first 14 days of a normal
28-day monthly cycle. When the follicle is large and mature enough, it
is released into the tubes, marking the ovulation. The ovarian follicle
produces estradiol (E2), which ensures that the uterine endometrium
develops again after the menstruation.
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After the ovulation, the empty ovarian follicle evolves into
progesterone (corpus luteum). The high amounts of progesterone produced
(P), prepare the uterine endometrium for the possible arrival of an
embryo. If a pregnancy occurs, the progesterone is retained and
menstruation ceases. If not, the progesterone is degraded, the levels
fall and menstruation sets in. In this complicated sequence many things
can go wrong. In the beginning of a treatment the levels of these
hormones are determined by blood tests, as well as an ultrasound
examination in order to determine the condition of the ovaries and of
the endometrium.
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