Functions OF FOLICLE STIMULATING
Gonadotropins: Luteinizing and Follicle Stimulating Hormones
Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are called gonadotropins
because stimulate the gonads - in males, the testes, and in females, the ovaries. They are not
necessary for life, but are essential for reproduction. These two hormones are secreted from
cells in the anterior pituitary called gonadotrophs. Most gonadotrophs secrete only LH or FSH,
but some appear to secrete both hormones.
As describef for thyroid-simulating hormone, LH and FSH are large glycoproteins composed of
alpha and beta subunits. The alpha subunit is identical in all three of these anterior pituitary
hormones, while the beta subunit is unique and endows each hormone with the ability to bind
its own receptor.
PHYSIOLOGIC EFFECTS OF GONADOTROPINS
Physiologic effects of the gonadotrophins are known only in the ovaries and testes. Together,
then regulate many aspects of gonadal function in both males and female
FOLLICLE STIMULATING HORMONE (FSH)
FSH is a glycoprotein hormone, produced in the anterior pituitary and released into
the blood in response to GnRH (GnRH is released from the hypothalamus).
Glycoprotein hormones are protein hormones with carbohydrate chains. This
carbohydrate group protects the FSH molecule from rapid breakdown and
metabolism. This shielding group adds to the hormone's half-life, which in most
species is several hours.
The FSH is transported to the ovary, enters the developing follicle, and stimulates
the granulosa cells to produce oestrogen. Granulosa cells are a type of cells lining
FSH is also responsible for growth of the follicle, involving both an increase in the
number of granulosa cells and secretion of follicular fluid.
Peak blood concentrations of FSH occur in mid-dioestrus approximately 10 days
before ovulation. This stimulates initial follicular growth (not usually palpable
within the ovaries). Low concentrations of FSH are found during oestrus.
As the follicle grows, the granulosa cells secrete a hormone called inhibin into the
follicular fluid. This hormone is carried, through the vascular system, back to
the anterior pituitary where it suppresses the secretion of FSH.
LUTEINIZING HORMONE (LH)
Similar to FSH, LH is produced in the anterior pituitary and is a
glycoprotein hormone, although the carbohydrate group is different from FSH.
LH is released due to the influence of GnRH from the hypothalamus. The LH is
transported to the ovary and stimulates the theca cells surrounding the follicle to
Circulating concentrations of LH are low in the late luteal phase. Initial
rise occurs in early oestrus and reaches peak values after ovulation. In the mare,
this hormone stimulates major follicular growth, maturation and ovulation. Values
decrease as progesterone concentrations (from the developing CL) rise.
Both FSH and LH have two modes of delivery. One mode is "tonic",
which maintains low blood hormone levels.
The second mode is a "surge", which results in a sharp increase or peak in the
level of the gonadotropin. Both of these delivery modes are required at various
times throughout the estrous cycle.
CONTROL OF GONADOTROPIN SECRETION
The principle regulator of LH and FSH secretion is gonadotropin-releasing
hormone(GnRH, also known as LH-releasing hormone). GnRH is a ten amino acid
peptide that is synthesized and secreted from
hypothalamic neurons and binds to receptors
As depicted in the figure to the right,
GnRHstimultes secretion of LH, which in
turn stimulates gonadal secretion of the sex
steroids testosterone, estrogen and
progesterone. In a classical negative
feedback loop, sex steroids inhibit secretion
of GnRH and also appear to have direct negative effects on gonadotrophs.
This regulatory loop leads to pulsatile secretion of LH and, to a much lesser extent,
FSH. The number of pulses of GnRH and LH varies from a few per day to one or
more per hour. In females, pulse frequency is clearly related to stage of the cycle.
Numerous hormones influence GnRH secretion, and positive and negative control
over GnRH and gonadotropin secretion is actually considerably more complex
than depicted in the figure. For example, the gonads secrete at least two additional
hormones - inhibin and activin - which selectively inhibit and activate FSH
secretion from the pituitary.
FUNCTIONS OF CORTISOLS:
Cortisol is an important hormone in the body, secreted by the adrenal glands and involved in the
following functions and more:
Proper glucose metabolism
Regulation of blood pressure
Insulin release for blood sugar maintanence
Normally, it’s present in the body at
higher levels in the morning, and at
its lowest at night. Although stress
isn’t the only reason that cortisol is
secreted into the bloodstream, it
has been termed “the stress
hormone” because it’s also secreted
in higher levels during the
body’s „fight or flight‟ response to
stress, and is responsible for
several stress-related changes in
the body. Small increases
of cortisol have some
A quick burst of energy for survival
Heightened memory functions
A burst of increased immunity
Lower sensitivity to pain
Helps maintain homeostasis in the body
While cortisol is an important and helpful part of the body’s response to
stress, it’s important that the body’s relaxation response to be activated so the
body’s functions can return to normal following a stressful event.
Unfortunately, in our current high-stress culture, the body’s stress response
is activated so often that the body doesn’t always have a chance to return to
normal, resulting in a state of chronic stress.
Higher and more prolonged levels of cortisol in the
bloodstream (like those associated with chronic stress)
have been shown to have negative effects, such as:
Impaired cognitive performance
Suppressed thyroid function
Blood sugar imbalances such as hyperglycemia
Decreased bone density
Decrease in muscle tissue
Higher blood pressure
Lowered immunity and inflammatory responses in the body, slowed wound healing, and other
Increased abdominal fat, which is associated with a greater amount of health problems than
fat deposited in other areas of the body. Some of the health problems associated with
increased stomach fat are heart attacks, strokes, the development of metabolic syndrome,
higher levels of “bad” cholesterol (LDL) and lower levels of “good” cholesterol (HDL),
which can lead to other health problems!
To keep cortisol levels healthy and under control, the body’s relaxation
response should be activated after the fight or flight response occurs. You
can learn to relax your body with various stress management techniques,
and you can make lifestyle changes in order to keep your body from reacting
to stress in the first place. The following have been found by many to be
very helpful in relaxing the body and mind, aiding the body in maintaining
healthy cortisol levels:
Cortisol secretion varies among individuals. People are biologically ‘wired’ to
react differently to stress. One person may secrete higher levels of cortisol than
another in the same situation. Studies have also shown that people who secrete
higher levels of cortisol in response to stress also tend to eat more food, and food
that is higher in carbohydrates than people who secrete less cortisol. If you’re
more sensitive to stress, it’s especially important for you to learn stress
management techniques and maintain a low-stress lifestyle.
(functions of cortisols animation)