Download HAP - Unit 7 - Pituitary Glands - bushelman-hap

Pituitary gland.
The pituitary.
The pituitary Gland.
Pituitary Gland
• Is also known as Hypophysis
• Sits in the small bony cavity Sella Turcica at
the base of the brain.
• Secretes hormones regulating homeostasis
including trophic hormones that stimulate
other endocrine glands.
• 3 lobes-Adenohypophysis also known as the
anterior pituitary and the neurohypophysis
also known as the Posterior hypophysis.
Pituitary Gland
• Also an intermediate lobe that secretes
MSH.Rudimentary.
• Anterior pituitary synthesize and secretes
ACTH, LH,FSH,GH,TSH,prolactin.
• Posterior pituitary secretes oxytocin and
ADH.
• Posterior lobe is connected to the
hypothalamus through the pituitary stalk
• Hormones are actually made in the nerve cell
bodies of the hypothalamus and then
transported down the posterior pituitary
ACTH
• Is a polypeptide
• Acts on the adrenal cortex
• Secreted in response to the corticotropinreleasing hormone (CRH) from the
hypothalamus.
• Consists of 39 amino acids and 13 may be
cleaved to (MSH).
• Hypocortisolism and Addison’s disease have
tanned skin.
• Stimulates the cortex of the adrenal gland to
produce corticosteroids, mainly glucocorticoids.
• Excess ACTH-Addison’s disease
Small cell carcinoma
Congenital Adrenal hyperplasia
Cushing’s syndrome.
TSH
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Is a glycoprotein
Also known as Thyrotropin
2 subunits
α and β
α is identical to HCG,LH,FSH
β subunit is unique to TSH therefore determines
its function.
• Stimulates thyroid gland to secrete T3, T4
• Controlled by Thyrotropin-releasing hormone
(TRH)
TSH (ctd)
• Stimulating antibodies to this receptor
mimic TSH action and found in grave’s
disease.
Luteinising Hormone
• A glycoprotein
• Also known as Lutropin
• Acts in concert with Follicular stimulating
hormone
• Play a part in normal reproductive function.
• In females, an acute rise triggers ovulation.
• In males, stimulates leydig cells to produce
testosterone.
• Controlled by Gonadotropin-releasing hormone.
Follicle Stimulating Hormones.
• A glycoprotein.
• Acts in synergy with LH.
• In women, stimulates the growth of immature
Graafian follicles to maturation.
• In men, enhances production of sperm cells.
• Half life of 3-4 hrs.
• Controlled by Gonadotrophin-releasing
hormones .
• High in menopause and low in childhood.
• High levels is indicative of defective feed-back
from the gonads.
FSH (ctd)
• High levels is typical in menopause, but
abnormal in reproductive years and may be a
sign of------- Premature menopause
Gonadal dysgenesis,
Castration.
Testicular failure.
Low levels is seen in.. Kallman syndrome
Hypopituitarism
Hypothalamic causes
Drugs-GnRH antagonists.
Prolactin
• A peptide hormone
• Associated with lactation.
• In breast feeding, suckling reflex—
prolactin production—Fills breast with milk
(lactogenesis)
• Production is regulated by neuroendocrine
neurons of the hypothalamus.
Growth Hormone
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Also known as Somatotropin.
A protein hormone.
Stimulates growth and cell production.
Excess GH leads to acromegaly and Gigantism.
Highest amount of GH is secreted during
puberty.
• Regulated by GHrH and somatostatin.
• Other stimulators are.. Sleep, exercise, Reduced
blood sugar, dietary protein, estradiol.
• Inhibitors are ..somatostatin, circulating GH,
Dietary carbohydrates, glucocorticoids.
Regulation of GH
• GH release is stimulated by the GHrH
• Which act on somatomedins(IGF-1
somatomedinC)
• Act to increase growth of cells, cartilage and
protein metabolism.
• GH release is inhibited by Somatostatins which
are produced in the hypothalamus.
• Secretion of somatostatins is stimulated by
increased circulating levels of GH.
• Other sites where we find somatostatins are the
GIT and pancreas.
Gigantism
Acromegaly
Dwarfism
• Can be due to GHrH deficiency, GH
deficiency or other cause.
• Extreme shortness
• But proportional body parts.
• Other causes not due to pituitary GH are
osteodystrophy, achondroplasia.
Oxytocin
• In females, released in large amounts after
distension of the cervix and vagina during labor.
• Actions. let-down reflex and uterine contraction
in lactating mothers.
• Acts on the mammary glands causing milk letdown into collecting chamber where it is
extracted by suckling the nipple.
• Suckling produces stimulation of the neurons
that make oxytocin to fire action potential which
results in pulses of oxytocin from the pituitary.
Oxytocin
• Also important for uterine contraction—
important for cervical dilatation before birth
at the 2nd and 3rd stages of labor.
• During breastfeeding, causes mild but
painful contractions of the uterus during
the first few weeks of lactation.
• Other actions.. sexual arousal and
bonding-monogamous pair bond.
Antidiuretic Hormone
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A peptide hormone.
Also known as vasopressin.
Released during dehydration.
Regulates retention of water within the body.
Act by increasing the permeability of the
collecting duct to water and allows water
reabsorbtion and excretion of small volume of
concentrated urine.
Also induces moderate vasoconstriction.
Regulation—Reduced plasma volume--increased production.
Other influences are caffeine and ethanol which
reduces secretion.
Angiotensin II stimulates secretion.
Pituitary insufficiency
• The changes that develop in pituitary
insufficiency are predictable in terms of the
known hormonal functions of the gland
• In hypopituitarism, the adrenal cortex atrophies.
• They develop reduced glucocorticoids and sex
hormones.
• Initially,no mineralocorticoid deficiency
• Growth is inhibited,
• Thyroid function is depressed
• The gonads atrophy
• Sexual cycles stop
• Some secondary sexual characteristics
disappear.
Pituitary Hyper function
• Usually due to tumors of the pituitary
• Cause symptoms of hyper secretion of the
hormones.