Female hormones and
infertility
The main feature of the reproductive years of women's
menstrual cycle. This process, in which an egg (oocyte) matures and is
released each month ready for fertilization, is controlled by an elaborate
system involving the gonadotropic hormones.
A monthly menstrual cycle of women occurs in three phases:
-
Follicular phase:
Days 1 to 13.
-
Ovulatory phase:
Around 14th.
-
Luteal phase: Days
15 to 28.
The cycle is controlled by the following hormones:
- Follicle-stimulating hormone (Follicle
stimulating hormone,. FSH)
- Hormone (Luteinizing hormoneLH)
- Estrogen
- Progesterone
The days of a menstrual cycle is marked by the first day
of menstrual blood. The first phase of the cycle is called the follicular
phase and lasts for about 14 days. The second phase, after ovulation has
occurred, is called the luteal phase (1).
The number of eggs that a woman can produce in its lifetime is determined
before birth. During embryonic life, millions of stem cells special is
produced in the ovaries. Many of them degenerate but the standings are ready
to develop and become mature eggs over time.
Three months before ovulation, up to 300 eggs were recruited to growth and
development. Each egg is a fluid-filled sac or 'hair', which surrounds and
nourishes during development (5). About two weeks before ovulation, the
secretion of FSH increases (3), stimulating the growth and development of
follicles. The growing follicles secrete increasing amounts of the hormone
estrogen (4), which causes the lining of the uterus (or endometrium) to
thicken (6) and promotes changes in the cervical mucus that allow optimal
penetration of sperm.
Under the influence of FSH, a follicle 'dominant' grows and matures faster
than others, which then degenerate (5). About 32 hours before ovulation,
estrogen secretion reaches its peak, triggering a peak production of LH
(3.4). This triggers the release of the mature egg from the dominant
follicle (5). The remnants of the follicles are then transformed into the
corpus luteum, which secretes progesterone to prepare the endometrium for
implantation (5). Due to progesterone, the body temperature rises (2).
If the egg is not fertilized by a sperm within 72 hours of his release from
the follicle, the corpus luteum will ultimately degenerate and menstruation
occurs (5). However, if fertilization occurs and the resulting embryo
continues its development, is produced hCG. This causes the corpus luteum
secretes two hormones, estrogen and progesterone, to ensure favorable
conditions for the implantation of the fertilized egg. In fact, the presence
of hCG in serum or urine is the first indicator of early pregnancy.
Last updated: 24/02/2012
