Hormones of
Pituitary Gland
• Also called
hypophysis or master gland
– Also
directs other glands to secrete hormones
• Pituitary
gland is situated at the base of the brain, directly below hypothalamus
– Behind the
bridges of nose
– in an
indent in the sphenoid bone called sella turcica
• The word
pituitary has its origin in
– Greek: ptuo means “to spit”
– Latin: Pituita means “mucus”
• Mucus was
produced by the brain and was excreted through the nose by the pituitary
• Pituitary is
a pea sized, bean shaped bi-lobed gland, that are further subdivided into areas
called ‘parses’
– Anterior
lobe
• Also
known as Adenohypophysis
• Consist
of about 80% of the gland
– Posterior
lobe
•
Also called Neurohypophysis
•
Anterior lobe has two divisions
– Pars
distalis
•
Largest
•
Hormone producing cells – Pars tuberalis
•
Upward extension to the anterior lobe and
attached to pituitary stalk
•
Posterior lobe – Pars nervosa
•
Pars intermedia (Median part connecting two lobes) – Poorly
defined in the human
•
Both lobes secrete differently from eachothers • Hormones of
Anterior pituitary are:
– Growth
hormone: Promotes growth
– Adrenocorticotropin
(ACTH): Controls adrenal cortex
– Thyroid
stimulating hormone (TSH): Controls thyroid
– Prolactin:
Development of breasts & milk secretion
– Gonadotropic
hormones
• Follicle
stimulating hormone (FSH)
• Luteinizing
hormone (LH)
– FSH:
Stimulates follicle growth in ovaries & maturation of sperms in testes
– LH:
Ovulation, corpus luteum, estrogen & progesteron secretions from ovaries
and stimulate testosteron synthesis in male
• Hormones of
posterier pituitary are:
– Antidiuretic hormone (ADH)
(Vassopressin)
• Increase
water reabsorption by kidneys
• Cause
vasoconstriction
• Increase
blood pressure
– Oxytocin
• Milk
ejection and uterine contraction during birth
• Melanophore
stimulating hormone is secreted by pars intermedia (median part) of pituitary
• The
secretions of pituitary are regulated by hypothalamus
• Control of
Pituitary Secretions:
i) Nervous mechanism
–
Regulatory factors are released from hypothalamus ii)
Hormonal mechanism
–
Feedback inhibition controls their release
• Both
Nervous & Hormonal control of overall endocrine system is coordinated by
hypothalamus
• Hypothalamus:
• Specialized
center in the brain that functions as master coordinator of hormonal action
– Connected
directly to pituitary stalk
• Pituitary
stalk have a portal system of blood vessels to maintain the proper secretory
activity
• Pituitary
is supplied from carotid artery
– Hypophyseal
arteries & veins
– 80 to 90%
to anterior lobe
– Posterior
lobe is rich in unmyelinated nerve supplies
• The
neurosecretory cell in hypothalamus releases regulatory
factors through their axons to the capillary beds in anterior lobe
– Hypothalamic
releasing factors or hormones
– Hypothalamic
inhibitory factors or hormones
• The
regulatory factors of hypothalamus stimulate pituitary cells to secrete or
inhibit hormones
• Secretory
cells in anterior pituitary are:
– Somatotropes:
human Growth Hormone (hGH)
– Corticotropes:
ACTH
– Thyrotropes:
TSH
– Gonadotropes:
Gonadotropi hormones (FSH, LH)
– Lactotropes:
PRL
• Posterior
pituitary hormones are synthesized by cell bodies of neurosecretory cells in
hypothalamus
• Major
hypothalamic releasing and inhibitory hormones are:
– Thyrotropin
Releasing Hormone (TRH): Releases TSH
– Corticotropin
Releasing Hormone (CRH): ACTH
– Gonadotropin
Releasing Hormone (GnRH)
• Stimulate
the release of gonadotropic hormones (FSH, LH)
– Growth
Hormone-releasing Hormone (GHRH)
• Releases
growth hormone from anterior pituitary
– Growth
Hormone Release-Inhibiting Hormone
(GRIH)
• Inhibit
secretion of GH from somatotropes
– Prolactin
Release-Inhibiting Hormone (PLRIH)
• Inhibit the
release of prolactin
– Melanocyte
Stimulating Hormone-Release Hormone
• Release MSH
from pars intermedia
– Melanocyte
Stimulating Hormone-Release inhibiting hormone (MSHRIH)
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