Hormonal coordination 2
Hormones produced by
Anterior Pituitary and
Hypothalamus
Pituitary
Pituitary (hypophysis)
• Pea shaped structure 1-1.5cm diameter,
• Attached to hypothalamus through a stalk
(infundibulum)
• Anterior pituitary
• Posterior pituitary
– contain axons
Hypothalamus
Neurons of
Hypothalamus
Pituitary
stalk
Posterior pituitary
Anterior
pituitary
Anterior pituitary (adenohypophysis)
• Secretes seven hormones
• Five main types of cells in the Anterior
pituitary
Somatotrophs, thyrotrophs, gonadotrophs,
lactotrophs, corticotrophs
• Somatotrophs produce hGH
• Thyrotrophs
produce TSH
• Gonadotrophs produce FSH & LH
• Lactotrophs produce Prolactin
• Corticotrophs produce ACTH & MSH
hGH (human growth hormone)
Most abundant pituitary hormone
Target tissue: all body cells specially
- bone,
- cartilage,
- liver
- muscle
Effects of hGH on target tissues
1. cause body cells to grow
2. regulate metabolism
- stimulate protein synthesis & inhibits
protein breakdown,
- stimulate lipolysis,
- slow down use of glucose for ATP
production
3. Promote synthesis & secretion of “insulin
like growth factors” (increase growth)
Disorders associated with hGH
• Pituitary dwarfism (under production of hGH
during growth years,) slow bone growth, &
other organs
• Giantism (over production of hGH during
childhood), abnormal increase in length of long
bones
• Acromegaly (over production of hGH during
adulthood), bones of hands, feet, cheeks, jaws
thicken, other tissues also grow, enlarged eye
lids, lips, nose
TSH (Thyroid stimulating hormone)
• Target tissue : thyroid gland
• Stimulate synthesis & secretion of
thyroxin & triiodothyronin from thyroid
gland
FSH (follicle stimulating hormone)
• Target tissues: ovary & testes
• Ovary
– Initiate development of follicles each month
– Stimulate follicular cells to secrete estrogen
• Testes
– Stimulate sperm production
LH (Luteinizing hormone)
• Target tissues: ovary & testes
• Ovary – together with FSH stimulate
– secretion of estrogens by ovarian cells
– Ovulation
– Stimulate formation of corpus luteum in
the ovary
– Secretion of progesteron by corpus luteum
LH (Luteinizing hormone)
• Testes
– Stimulates interstitial cells in testes to
develop & secrete testosterone
Prolactin
• Target tissue : mammary glands
• Effect: Together with other hormones,
initiate & maintain milk secretion by
mammary glands
• Disorders: overproduction causes
absence of menstrual cycles in
females, impotence in males
ACTH (Adrenocorticotropic hormone)
• Target tissue : adrenal cortex
• Effect:
Stimulates adrenal cortex to produce &
secrete glucocorticoid hormones
MSH (melanocyte stimulating hormone)
• Target tissue : melanocytes in the skin
• Excessive MSH increases skin
pigmentation
Regulation of anterior pituitary
hormones
Regulation of secretion of anterior
pituitary hormones
1. Hormones secreted by hypothalamus
•
•
five hypothalamic releasing hormones,
two release inhibiting hormones
2. By negative feed back from target
endocrine gland hormones
Hypothalamic releasing hormones
1. GHRH (growth hormone releasing
hormone) –stimulate release of hGH
2. TRH (thyrotropin releasing hormone) –
stimulate release of TSH & hGH
3. GnRH (gonadotropin releasing hormone)
stimulate release of LH & FSH
4. PRH (prolactin releasing hormone)
5. CRH (Corticotropin releasing hormone)
stimulate release of ACTH & MSH
Hypothalamic release inhibiting
hormones
1. GHIH (growth hormone inhibiting
hormone)
- inhibits release of hGH & TSH
2. PIH (prolactin inhibiting hormone)
- Inhibits secretion of prolactin
Hypothalamo-pituitary portal system
• Releasing or release inhibiting hormones
synthesized in hypothalamus and secreted
by neuro-secretary cells of hypothalamus
• They are carried in portal veins to
anterior pituitary where they stimulate or
inhibit secretary cells
Neurons of the
hypothalamus
Median eminence
Portal veins
Hypothalamic
hormones
Ant. Pituitary
hormones
Endocrine cells
of Ant. pituitary
Ant. Pituitary
hormones
_
Higher brain centers
_
Hypothalamic neurosecretary cells
Two Release inhibiting
hormones
Five Releasing
hormones
_
Anterior pituitary
hGH +/-, Prolactin +/MSH +
Non-endocrine
target tissue
TSH +/-, ACTH +
FSH & LH (+)
Endocrine
target tissue
-ve feedback
Hormones released by posterior
pituitary
• ADH, Oxytocin
• Hormones synthesized by cell bodies of
the neurosecretory cells in the
hypothalamus
• Axons of these neurons ends in posterior
pituitary
Hypothalamus
Neurons of
Hypothalamus
Pituitary
stalk
Posterior pituitary
Anterior pituitary
Oxytocin
Target tissues (During & after delivery of a baby)
• Mother’s uterus-smooth musclesDuring delivery oxytocin enhances contraction of
the wall of the uterus
• Mother’s breasts-mammary glands Stimulates milk ejection from the mammary
glands in response to the mechanical stimulation
provided by the suckling infant
ADH
Target tissues
• Kidney-distal convoluted tubules,
collecting ducts reabsorb more water from
the urine (decrease urine volume)
• Sweat glands -decrease water loss by
perspiration from skin
• Arterioles-constrict arterioles which
increase blood pressure