Download The endocrine system (overview) The endocrine system (overview)

10/28/2010
The endocrine system
(overview)
Primary text: Vander’s physiology,
Chapter 11
Result of growth
hormone deficiency
Result of growth
hormone overproduction
Thyroid hormone
overproduction
A pump for insulin delivery
Principle of endocrine signalling
Endocrine
gland
Target
Cell-1
Target
Cell-2
Hormone
Target
Cell-3
Hormones are used for long range intercellular communication within the body.
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The endocrine system: a system of endocrine
(ductless) glands or specialised cells which can secrete
hormones directly into local capillaries for distribution
around the body.
ENDOCRINE
(traditional)
For a molecule to be classifiable as a
hormone it must:
a) be synthesised and secreted by specific type of
cells
(NB: these are not always anatomically distinct cells
assembled as a “gland” i.e. vitamin D3 is produced by skin
cells)
b) be secreted into the blood stream and travel in
the blood
c) bind to specific receptors on target cells, where
it exerts various actions
d) In addition, hormones often affect metabolism, cell
division, gene expression.
HORMONES ARE EITHER:
1. Derivatives of the amino acid
tyrosine:
a) catecholamines
(adrenaline and noradrenaline)
b) thyroid hormones
thyroxine (T4) and triiodothyronine (T3)
I
I
I
I
2. Proteins/peptides – long chains of aminoacids
(eg insulin)
3. Steroids: eg cortisol, tesosterone
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Secretion of hormones is regulated by:
1. Ca2+ -dependent exocytosis (pituitary hormones, insulin, adrenaline)
Ca2+
Synthesis - storage in
vesicles - vesicle fusion
with the membrane –
hormone release.
2. By cleavage of the storage molecules (thyroid hormones –
from thyroglobulin).
3. Adrenal steroids: little storage but massive pool of the
precursors: synthesised on command (ACTH) and immediately
secreted.
Some of the endocrine glands in man
ACTH, GH, LH,
FSH, TSH, PROLACTIN
hypothalamus
ADH, OXYTOCIN
Thyroxine (T4)&
triiodothyronine (T3)
Calcitonin
Cortisol, aldosterone
Adrenaline
Insulin
Glucagon
Estrogens
Progesteron
Androgens
Organisation of the endocrine circuits which operate via anterior pituitary
Hypothalamus
Anterior
Pituitary
Endocrine
glands controlled
by pituitary
Targets throughout the body
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Hypothalamus
Mammary
glands
Uterus
Target endocrine glands
Tissues of the body
Organisation of the endocrine circuits which operate via anterior pituitary
HYPOTHALAMUS
RELEASING (INHIBITORY)FACTORS (HORMONES) ANTERIOR
PITUITARY
“Trophic”
Trophic hormones
hormones
TSH
TARGET ENDOCRINE GLANDS
Thyroid
Adrenal
cortex
thyroxine
cortisol
HORMONES ACTH
FSH LH
FSH, LH
Gonads
sex steroids
TARGET TISSUES AND ORGANS
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HYPERthyroidism
(Toxic goiter)
HYPOthyroidism
(cretinism)
Hypothalamus
Posterior
y
Pituitary
A direct channel
Targets throughout the body
Hypothalamus
Vasopressin
Oxytocin
(anti-diuretic
hormone)
Tissues of the body
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There are many hormones produced by specialised
cells in various organs which are not controlled by the
pituitary.. In some cases these are “true” glands,
pituitary
sometimes just groups of specialised cells present in
various tissues.
“True” glands
“Groups of cells”
Pancreas
cells in kidney
Cells in the atria of
the heart
Renin-producing
i
d i
Adrenal medulla
Targets throughout the body
Blood glucose
Insulin
Endocrine gland
ANTERIOR
PITUITARY
Major hormone
Primary targets
Trophic hormones Other
~endocrine~
glands
and various
tissues
ACTH
(adrenocortico…)
TSH (thyroidstimulating...)
Adrenal cortex
LH (luteinizing
hormone
{corpus luteus –
yellow body}
Ovaries
Testes
Female
hormones↑
Ovulation
Male hormones↑
FSH (folliclestimulating…)
Ovaries
Testes
Follicle growth ↑
Sperm formation ↑
GH (growth…)
Liver, cartilages,
muscles,
many other
Breasts
Growth of almost
all types of cells.
Prolactin
POSTERIOR
PITUITARY
Primary effects
Stimulate
hormones
secretion and
proliferation of
the organs’
tissue
Secretion of
cortisol ↑
Secretion of T3
and T4 ↑
ADH (antidiuretic…)
also called
VASOPRESSIN
OXYTOCIN
Thyroid
kidneys, higher
concentrations –
blood
vessels
Uterus
Mammary glands
Growth of tissue
and milk
expression
H2O retention and
vasoconstriction,
BP increase
Contraction
Milk expression
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Endocrine gland
Major hormone
THYROID
Thyroxine (T4) &
tri-iodothyronine (T3)
Primary targets
Calcitonin
Bone
PARATHYROIDS
Parathyroid hormone
Bone, intestine, kidneys
ADRENAL cortex
Cortisol
Liver, muscles, immune
cells etc…
Most organs
(glucocorticoid)
Aldosterone
Kidneys
ADRENAL medulla
Adrenaline&
Noradrenaline
Cardio-vascular system,
lungs, liver
PANCREAS, islets of
Langerhans
Insulin
many cells
Glucagon
Liver and fat
ESTROGENS, mainly
estradiol
Female genitals,
mammary glands
GESTAGENS, i.e.
progesterone
Uterus
Testosterone
Prostate, seminal vesicles,
other organs
OVARIES
Mammary glands
TESTES
Primary effects
Rate of cell respiration↑
overall metabolism ↑
CNS: excitability &
emotional reactivity ↑
growth (young children)↑
Ca2+ concentration in
blood↓
Ca2+ concentration in
blood↑
“Stress” hormone, glucose
and fatty acids
mobilisation, protein
catabolism↑
Na+ retention,
K+ excretion
Blood pressure↑, blood
glucose↑, components of
fight-or-flight status
Cellular uptake of glucose,
formation of glycogen and
fat. Blood glucose ↓
Breakdown of glycogen
and fat. Blood glucose ↑
Develop female sex
charateristics. Increase sex
drive (central effect).
“Pro-gestational” action –
decrease in excitability and
contractility
Development of the
secretory tissue
Promotes male secondary
sex characteristic, skeletal
muscles: “anabolic” effect.
RECEPTORS:
Located intracellular
Located at the membrane
Receptors which operate
via gene expression
(steroid and thyroid
hormones)
Receptors which themselves
are ion channels (“A”)
Hormones act
on
Receptors which act as
enzymes
y
(for
(
example,
p
the
insulin receptor)
Receptors which are
coupled via G-proteins (for
example adrenalin
receptors)
Intracellular receptors may be located as free-floating
proteins in the cytoplasm or nucleus
DNA
GENE expression
CHANGE
of cell
function
Protein
Synthesis
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RECEPTORS:
Located intracellulary
Located at cell membrane
Receptors which operate
via gene expression
(steroid hormones)
Receptors which themselves
are ion channels (“A”)
Receptors which act as
y
(
p
enzymes
(for
example,
the
insulin receptor)
Hormones act
on
Receptors which are
coupled to their targets via
G-proteins (for example
adrenalin receptors)
Receptors which act as enzymes
-PO4
-PO4
-PO4
Changes in -PO
4
-PO
cell’s proteins
-PO4
4
-PO
4-PO4
-PO
4
-PO
-PO4 4
Cell response
RECEPTORS:
Located intracellularly Located at cell membrane
Receptors which operate
via gene expression
(steroids)
Hormones act
on
Receptors which themselves
are ion channels (“A”)
Receptors which act as
enzymes (kinases, for
example,
l the
h insulin
i
li
receptor) or directly
coupled to enzymes
Receptors which are
coupled via G-proteins (for
example adrenalin
receptors)
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Boy-ohboy!!!!!!
Medical importance of endocrine
system
1. Numerous diseases result from pathologically low or
high concentration of hormones:
- diabetes (two forms due to insufficiency of 2 different
hormones)
- dwarf
dwarfism
sm and gigantism
g gant sm
- many forms of infertility and many more...
2. Numerous drugs act like hormones or their antagonists:
- bronchial asthma (allergic constriction of bronchi)
- prevention of pregnancy (contraception)
- treatment of hormonal diseases
- to enhance muscle growth (illegal doping!)
3. Numerous unwanted (side-) effects of drugs are due to
their interactions with hormones
Questions to consider:
- Concentration of which hormones are
likely to be elevated during pregnancy?
- What would happen to blood glucose levels
if a bulk dose of insulin was injected?
- Why
Wh is
i it common practice
ti to
t check
h k blood
bl d
concentrations of thyroid hormones in newborn children?
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