Transcript REPRODUCTIVE HORMONES FEMALE REPRODUCTIVE HORMONES GnRH  Estrogen  Progesterone  FSH  LH  hCG (human chorionic gonadotropin)  Oxytocin  Prolactin 

REPRODUCTIVE HORMONES
FEMALE REPRODUCTIVE HORMONES
GnRH
 Estrogen
 Progesterone
 FSH
 LH
 hCG (human chorionic gonadotropin)
 Oxytocin
 Prolactin
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The hypothalamus secretes
GnRH, causing the pituitary
to release FSH and LH
FSH stimulates a follicle to
develop and begin producing
estrogen. Occurs during
follicular phase.
 Low [estrogen] early in the
cycle inhibits the pituitary so
FSH and LH remain low.
 High [estrogen] later in the
cycle stimulates both the
hypothalamus and pituitary to
secrete hormones.

As a result, [LH] increases.
 LH induces the final maturation
of the follicle and ovulation (the
midpoint of the ovarian cycle).
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Estrogen triggers the
thickening of the endometrium
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The increase in LH stimulates
the corpus luteum which then
begins secreting progesterone
and estrogen (luteal phase)
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These two hormones together
have a negative effect on the
hypothalamus and pituitary,
inhibiting the secretion of LH and
FSH.
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They also stimulate further growth
of the endometrium, strengthen the
uterus, inhibit further ovulation,
and prevent uterine contractions.
As the hypothalamus and
pituitary are inhibited, there is a
resulting decline in [LH].
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This causes the corpus luteum to
deteriorate.
The resulting lower [estrogen] and
[progesterone] allow the
hypothalamus and pituitary to
begin producing FSH and LH
which starts the cycle again
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If pregnancy does not
occur, the decrease in
[progesterone] triggers
uterine contractions and
the endometrium is shed,
marking the beginning of
flow phase.
Estrogen is also responsible
for female secondary sex
characteristics, including
deposition of fat in the
breasts and hips, increased
water retention, and
stimulation of breast
development.
hCG (human chorionic gonadotropin) – hormone
that maintains the corpus luteum for about 3
months
 Oxytocin – triggered by high levels of estrogen at
the end of pregnancy; produces contractions of
smooth muscle in uterus. After birth contributes
to production of milk
 Prolactin – hormone that stimulates mammary
glands to produce milk
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THE MENSTRUAL CYCLE
 Purpose:
to bring an egg to maturity and
to prepare the reproductive system for
pregnancy.
 28
day cycle (on average)
 Repeats
continuously until menopause
FOUR PHASES
1. Flow phase (5 days) – shedding of the endometrium
(if no fertilization occurs)
FOUR PHASES
2.

Follicular Phase (days 6-13) – development
of follicle within one of the ovaries
Follicles contain developing oocye (egg) and as they
develop begin to secrete estrogen
FOUR PHASES
3. Ovulation (day 14) – egg bursts from the ovary and
the follicle cells develop into the corpus luteum
FOUR PHASES
4. Luteal Phase (days 15-28) - development of the corpus
luteum
Corpus luteum secretes both progesterone and estrogen.
- Prepares uterus for an embryo
THE FULL CYCLE
MALE REPRODUCTIVE HORMONES

The hormonal control of the male reproductive
system is started in the hypothalamus.
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The hypothalamus produces GnRH which stimulates
the pituitary to release FSH and LH
FSH stimulates cells in the testes to help produce
sperm. These cells release a hormone (inhibin)
which inhibits the production of FSH. This
hormone also has this effect in females.
LH stimulates the cells which produce
testosterone.
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Testosterone is responsible for the primary and
secondary male sex characteristics.
Primary sex characteristics are associated with:
 the development of the vas deferens and other ducts
 development of the external reproductive structures
 sperm production
 sex drive (and some increase in general aggression).
 Secondary sex characteristics are features not directly
related to the reproductive system
 deepening of the voice
 distribution of facial and pubic hair
 secretion of body oils
 muscle growth.
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