B

1. Endocrinal system
Endocrinal system

2. Word Hormone is derived from a Greek word
Word Hormone is derived from a Greek word
“hormaein” which means
“hormaein” which means to execute or to
to execute or to
arouse.
arouse.
Term introduced by
Term introduced by Starling
Starling in 1905.
in 1905.
To define hormones are secretory
To define hormones are secretory
products of the ductless glands, which are
products of the ductless glands, which are
released in catalytic amounts into blood stream
released in catalytic amounts into blood stream
and transported to specific target organs where
and transported to specific target organs where
they elicit physiologic, morphologic and
they elicit physiologic, morphologic and
biological responses.
biological responses.

3. Different type of hormones are:
Different type of hormones are:
a)
a) Endocrine hormones:
Endocrine hormones:
These include the chemical
These include the chemical
messengers whose functions is the
messengers whose functions is the
transmission of a molecular signal from a
transmission of a molecular signal from a
endocrinal organ through a blood stream
endocrinal organ through a blood stream
to a distant target organ.
to a distant target organ.

4. b) Neurocrine hormones :
b) Neurocrine hormones :
It involves the release of
It involves the release of
chemical messengers from nerve terminals,
chemical messengers from nerve terminals,
which may reach their target cells via one of the
which may reach their target cells via one of the
three routes
three routes
1) neurotransmitters release directly into
1) neurotransmitters release directly into
intercellular space cross the synaptic junction,
intercellular space cross the synaptic junction,
and act on postsynaptic cell eg; Ach.
and act on postsynaptic cell eg; Ach.

5. 2) Neural signals can be transferred via gap
2) Neural signals can be transferred via gap
junctions.
junctions.
3) Neurohormones released from
3) Neurohormones released from
neurosecretory neuron into blood stream
neurosecretory neuron into blood stream
and then carried to distant target cells.
and then carried to distant target cells.
eg; ADH, Oxytocin.
eg; ADH, Oxytocin.

6. c) Paracrine hormones
c) Paracrine hormones
These are chemical messengers which
These are chemical messengers which
after getting secreted by a cell are carried
after getting secreted by a cell are carried
over short distance by diffusion through
over short distance by diffusion through
interstitial spaces to act on the
interstitial spaces to act on the
neighbouring cells. Eg; somatostatin
neighbouring cells. Eg; somatostatin
secreted by delta cells in islets of
secreted by delta cells in islets of
langerhans acts on alpha and beta cells.
langerhans acts on alpha and beta cells.

7. 4) Autocrine hormones
4) Autocrine hormones
These refer to those chemical
These refer to those chemical
messengers which are secreted by
messengers which are secreted by
specific cells into extracellular fluid
specific cells into extracellular fluid
surrounding the cell and which acts upon
surrounding the cell and which acts upon
very cells that secrete it. Eg; NE secreted
very cells that secrete it. Eg; NE secreted
by Adrenal medulla inhibits NE release by
by Adrenal medulla inhibits NE release by
those cells.
those cells.

9. Classification of hormones
Classification of hormones
4 general classes;
4 general classes;
1)
1) Proteins and polypeptides
Proteins and polypeptides
Mnemonic- 4P
Mnemonic- 4P
(Ant pit , post pit , pancreas, parathyroid)
(Ant pit , post pit , pancreas, parathyroid)
eg;
eg; hormones of ant. Pituitary,
hormones of ant. Pituitary, ADH,
ADH,
Oxytocin, insulin, glucagon, PTH
Oxytocin, insulin, glucagon, PTH

10. 2)
2) Steroids
Steroids
eg; hormones of adrenal cortex (Cortisol
eg; hormones of adrenal cortex (Cortisol
and aldosterone), ovaries(estrogen ,
and aldosterone), ovaries(estrogen ,
progesterone), testes( testosterone) and
progesterone), testes( testosterone) and
placenta( estrogen , progesterone).
placenta( estrogen , progesterone).

11. 3) Derivatives of amino acids
3) Derivatives of amino acids
eg; hormones of adrenal medulla( epi, NE)
eg; hormones of adrenal medulla( epi, NE)
and thyroid.
and thyroid.
4) Fatty acid derivatives- Eicosanoids
4) Fatty acid derivatives- Eicosanoids
Includes:
Includes:
Prostaglandins, prostacyclin, thromboxane
Prostaglandins, prostacyclin, thromboxane
Leukotrines
Leukotrines

12. Synthesis, storage and release of hormones
Synthesis, storage and release of hormones
1)
1) Amines or Amino acid derivatives
Amines or Amino acid derivatives
a)
a) Synthesis
Synthesis- synthesized in the cell cytoplasm.
- synthesized in the cell cytoplasm.
b)
b) Storage and release
Storage and release –
–
-Catecholamines are stored in secretory
-Catecholamines are stored in secretory
granules, secretion occurs when granules fuse
granules, secretion occurs when granules fuse
with the plasma membrane, causing extrusion
with the plasma membrane, causing extrusion
of contents in the circulation.
of contents in the circulation.

13. - Thyroid hormones are stored outside the
- Thyroid hormones are stored outside the
follicular cells in the form of thyroglobulin.
follicular cells in the form of thyroglobulin.
Secreted in blood by simple diffusion.
Secreted in blood by simple diffusion.
- Vit D is stored as a precursor in the skin.
- Vit D is stored as a precursor in the skin.

14. 2) Proteins and polypeptides hormones
2) Proteins and polypeptides hormones
a) Synthesis-
a) Synthesis-
In the ER of glandular cells.
In the ER of glandular cells.
b
b) Storage and release-
) Storage and release-
Stored in subcellular membrane bound
Stored in subcellular membrane bound
secretory granules within cytoplasm of
secretory granules within cytoplasm of
endocrine cell.
endocrine cell.
Released in blood by exocytosis.
Released in blood by exocytosis.

15. 3) Steroid hormones
3) Steroid hormones
a) Synthesis-
a) Synthesis-
Synthesized from cholesterol.
Synthesized from cholesterol.
Rate limiting step - transport of free
Rate limiting step - transport of free
cholesterol from cytoplasm to mitochondria
cholesterol from cytoplasm to mitochondria
b) Storage and release-
b) Storage and release-
little storage, Secreted in blood by
little storage, Secreted in blood by
simple diffusion.
simple diffusion.

16. Hormone secretion, Transport and
Hormone secretion, Transport and
clearance from the blood
clearance from the blood
-Some hormones are secreted within
-Some hormones are secreted within
sec after stimulation of the glands, and
sec after stimulation of the glands, and
their action takes sec. to min. Eg; epi and
their action takes sec. to min. Eg; epi and
NE.
NE.
- some hormones like thyroxine, GH
- some hormones like thyroxine, GH
require months for full effect.
require months for full effect.

17. Regulation of hormone
Regulation of hormone
secretion
secretion
 Feed back mechanism- most common
Feed back mechanism- most common
 Neural mechanism
Neural mechanism
 Rhythmic or chronotropic mechanism
Rhythmic or chronotropic mechanism
 Humoral mechanism
Humoral mechanism

18. Feedback control of hormone secretion
Feedback control of hormone secretion
a) Positive feedback
a) Positive feedback
b) Negative feedback
b) Negative feedback

19. a) Positive feedback
a) Positive feedback
it is less common. It acts to amplify
it is less common. It acts to amplify
initial biological effect of hormones.
initial biological effect of hormones.
Eg; LH surge which occurs d/t stimulatory
Eg; LH surge which occurs d/t stimulatory
effect of estrogen on ant. Pituitary before
effect of estrogen on ant. Pituitary before
ovulation. Secreted LH then acts on
ovulation. Secreted LH then acts on
ovaries to stimulate secretion of estrogen,
ovaries to stimulate secretion of estrogen,
which in turn causes more secretion of LH.
which in turn causes more secretion of LH.

20. b) Negative feedback-
b) Negative feedback-
The influence of blood conc. of
The influence of blood conc. of
the hormone concerned or its effect is to
the hormone concerned or its effect is to
inhibit further secretion of the hormones
inhibit further secretion of the hormones
and is called negative feedback.
and is called negative feedback.

21. The target organ hormones act either
The target organ hormones act either
on the ant. Pit. or on the hypothalamus,
on the ant. Pit. or on the hypothalamus,
usually by negative feedback control,
usually by negative feedback control,
which occurs at three levels;
which occurs at three levels;
1)
1) Long loop feedback
Long loop feedback
2)
2) Short loop feedback
Short loop feedback
3)
3) Ultra short loop feedback
Ultra short loop feedback

22. 1)
1) Long loop feedback
Long loop feedback
The peripheral gland
The peripheral gland
hormone eg; thyroid, adrenocortical and
hormone eg; thyroid, adrenocortical and
gonads can exert Long loop feedback on
gonads can exert Long loop feedback on
both the hypothalamus and ant. Lobe of
both the hypothalamus and ant. Lobe of
pit. It is usually negative occasionally can
pit. It is usually negative occasionally can
be positive.
be positive.

24. 2) Short loop feedback
2) Short loop feedback
The pituitary trophic
The pituitary trophic
hormones decrease the secretion of
hormones decrease the secretion of
hypophysiotropic hormones eg; GHRH,
hypophysiotropic hormones eg; GHRH,
GHIH, TRH, CRH and GnRH.
GHIH, TRH, CRH and GnRH.

25. 3) Ultrashort loop feedback
3) Ultrashort loop feedback
The hypophysiotropic hormones
The hypophysiotropic hormones
may inhibit their own synthesis and
may inhibit their own synthesis and
secretion via Ultrashort loop feedback
secretion via Ultrashort loop feedback

26. Neural control mechanisms
Neural control mechanisms
Secretion of hormone in response to external
Secretion of hormone in response to external
and internal stimuli.
and internal stimuli.
Eg.
Eg.
 Exercise
Exercise →
→ Sympathetic stimulation
Sympathetic stimulation →↑
→↑ EPI
EPI
& N E
& N E
 Stress
Stress →
→ ↑
↑CRH
CRH →↑
→↑ACTH
ACTH

27. Chronotropic control
Chronotropic control
 By rhythmic activity of neurons
By rhythmic activity of neurons
 Responsible pulsatile secretion
Responsible pulsatile secretion
 Includes:
Includes:
 Circadian rhythm ( 24-25hours rhythm)
Circadian rhythm ( 24-25hours rhythm)
 Diurnal rhythm (day night cycle)
Diurnal rhythm (day night cycle)
 Menstrual rhythm
Menstrual rhythm

28. Cyclical variation occurs in hormone
Cyclical variation occurs in hormone
release
release
There are variations influenced by seasonal
There are variations influenced by seasonal
changes, aging, diurnal cycle and sleep.
changes, aging, diurnal cycle and sleep.
Eg; GH secretion is more in early sleep.
Eg; GH secretion is more in early sleep.
cortisol secretion more early morning
cortisol secretion more early morning
melatonin during night time
melatonin during night time

29. Humoral control
Humoral control
By hormones & chemicals:
By hormones & chemicals:
Examples:
Examples:
 Glucagon stimulating insulin secretion
Glucagon stimulating insulin secretion
 Angiotensin II stimulating aldosterone
Angiotensin II stimulating aldosterone
secretion.
secretion.
 Na
Na+
+
- aldosterone
- aldosterone

30. “
“Clearance” of hormones from the blood
Clearance” of hormones from the blood
Metabolic clearance rate refers to
Metabolic clearance rate refers to
the sum of all the removal processes, ie
the sum of all the removal processes, ie
target cell uptake and degradation,
target cell uptake and degradation,
metabolic degradation and urinary or
metabolic degradation and urinary or
biliary excretion.
biliary excretion.
MCR=Rate of disappearance of hormone
MCR=Rate of disappearance of hormone
from the plasma/ Conc. of hormone in
from the plasma/ Conc. of hormone in
each ml of plasma.
each ml of plasma.

31. Hormone; Receptors and mechanism of
Hormone; Receptors and mechanism of
actions
actions
Characterstics of hormone receptors
Characterstics of hormone receptors
a)
a) Receptor specifity
Receptor specifity
b)
b) Receptor location ;
Receptor location ;
1) internal receptors:
1) internal receptors:
In the cytoplasm – steroid hormones
In the cytoplasm – steroid hormones
In the cell nucleus – thyroid
In the cell nucleus – thyroid
hormones
hormones

32. 2) external receptors; located in or on
2) external receptors; located in or on
plasma membrane of target cells. Eg;
plasma membrane of target cells. Eg;
protein , peptides and catecholamines
protein , peptides and catecholamines
c)
c) Receptor number-
Receptor number- It may vary. It is
It may vary. It is
regulated by two mechanisms
regulated by two mechanisms
1)
1) Down regulation
Down regulation: it refers to
: it refers to
decrease in number of active receptors. It
decrease in number of active receptors. It
occurs to regulate hormone sensitivity
occurs to regulate hormone sensitivity
when it is present in excess.
when it is present in excess.

33. it may occur as a result of –
it may occur as a result of –
a) inactivation of some receptors
a) inactivation of some receptors
b) inactivation of some of the intracellular
b) inactivation of some of the intracellular
protein signaling molecules
protein signaling molecules
c) Temporary sequestration of receptor to
c) Temporary sequestration of receptor to
inside of cell
inside of cell
d) Destruction of receptors by lysozymes
d) Destruction of receptors by lysozymes
after internalization
after internalization
e) Decreased production of receptors
e) Decreased production of receptors

34. 2) Upregulation :
2) Upregulation : it refers to increase in number
it refers to increase in number
of active receptors on a cell.
of active receptors on a cell.
APPLIED –
APPLIED –
In Type 2 diabetes increase in blood sugar
In Type 2 diabetes increase in blood sugar
level leads to increase conc of insulin leading
level leads to increase conc of insulin leading
to down regulation of INSULIN receptors on
to down regulation of INSULIN receptors on
liver cells, increasing subject’s resistance by
liver cells, increasing subject’s resistance by
decreasing sensitivity to this hormone.
decreasing sensitivity to this hormone.
Upregulation takes place after exercise.
Upregulation takes place after exercise.

35. Classification of receptors
Classification of receptors
A.
A. Cell membrane receptors
Cell membrane receptors
B.
B. Intracellular receptors
Intracellular receptors

36. Cell membrane receptors
Cell membrane receptors
 Ion channel linked receptors
Ion channel linked receptors
 G-protein coupled receptors
G-protein coupled receptors
 Receptor with tyrosine kinase
Receptor with tyrosine kinase
 Receptors linked with tyrosine kinase
Receptors linked with tyrosine kinase

37. Receptor
kinase
Receptor
linked
kinase
G-protein
coupled
receptor
Ion channel
linked
receptor

38. Mechanism of action of hormones
Group I hormones
• Bind with intracellular
receptors
• Lipid soluble
• Act by affecting gene
expression
• Slow mechanism (45m-
hours)
Eg. Steroids hormones,
Thyroid hormones
Group II hormones
• Bind with cell membrane
receptors
• Water soluble hormones
• Act through second
messengers
• On the basis of IInd
messengers the group II
hormones divided into 4
subgroups
On the basis of
mechanism of
action

39. Subgroup 2nd
messenger Hormones
Group II A cAMP ACTH, ADH, LH
Calcitonin, FSH, Glucagon, PTH
Group II B cGMP ANP, NO
Group II C IP3 & DAG ACh, Gastrin, oxytocin,
Group II D By tyrosine
kinases
GH, Insulin, Prolactin

40. Mechanism of action of Group I hormones
Mechanism of action of Group I hormones
Lipophilic hormone
Bind with cytoplasmic or nuclear receptor
Cross the cell
membrane
HR complex form
HR complex binds with hormone response element (HRE) of
DNA
m RNA formed
Formation of new proteins
Produced effects of

41. HORMONES acting through gene expression
HORMONES acting through gene expression
by binding of hormone with intracellular
by binding of hormone with intracellular
receptors -
receptors -
eg - steroid hormones
eg - steroid hormones
They increase protein synthesis.
They increase protein synthesis.
eg ; hormones of testes, ovaries, adrenal
eg ; hormones of testes, ovaries, adrenal
cortex.
cortex.
These proteins then function as enzymes,
These proteins then function as enzymes,
transport proteins, or structural proteins, which
transport proteins, or structural proteins, which
in turn provide other functions of the cells.
in turn provide other functions of the cells.

43. Mechanism of action of group II hormones
Mechanism of action of group II hormones
 Hormones are I messenger
Hormones are I messenger
 Effects by second messengers
Effects by second messengers
 Mostly involve activation G protein
Mostly involve activation G protein

44. Intracellular signaling after hormone receptor
Intracellular signaling after hormone receptor
activation
activation
Hormone bind to receptors to form
Hormone bind to receptors to form
Hormone- receptor complex. This activates the
Hormone- receptor complex. This activates the
receptors and initiates hormone effect.
receptors and initiates hormone effect.
1)
1) Ion channel-linked receptors
Ion channel-linked receptors
These receptors open or close for particular
These receptors open or close for particular
ions. Few hormones exert their action through
ions. Few hormones exert their action through
these Ion channel-linked receptors.
these Ion channel-linked receptors. Eg – NE,
Eg – NE,
ACh
ACh

45. 2) G protein linked hormone receptors
2) G protein linked hormone receptors
Many hormones activate receptors that
Many hormones activate receptors that
indirectly regulate the activity of target
indirectly regulate the activity of target
proteins by coupling with heterotrimeric
proteins by coupling with heterotrimeric
GTP- binding proteins (G proteins)
GTP- binding proteins (G proteins)
G proteins have 3 subunits namely
G proteins have 3 subunits namely α
α,
,β
β,
,γ
γ.
.

46. MOA
MOA- Hormone bind to receptors that are
- Hormone bind to receptors that are
coupled with G protein leading to conformational
coupled with G protein leading to conformational
change in receptor.
change in receptor.
- GDP is exchanged for GTP.
- GDP is exchanged for GTP.
-
- α
α subunit dissociate from the complex, and
subunit dissociate from the complex, and
associate with other intracellular signaling
associate with other intracellular signaling
proteins.
proteins.
- These proteins than alter the activity of ion
- These proteins than alter the activity of ion
channels or intracellular enzymes, which alters
channels or intracellular enzymes, which alters
cell function.
cell function.

48. Signal transduction pathway for
Signal transduction pathway for
hormone
hormone

49. Second messenger mechanisms for
Second messenger mechanisms for
mediating intracellular Hormonal functions
mediating intracellular Hormonal functions
second messanger systems that are
second messanger systems that are
activated through coupling of hormone-receptor
activated through coupling of hormone-receptor
complexes by G-protein include;
complexes by G-protein include;
1) Adenylyl cyclase-cAMP System
1) Adenylyl cyclase-cAMP System
2) Guanyl cyclase-cGMP System
2) Guanyl cyclase-cGMP System
3) calcium - calmodulin system
3) calcium - calmodulin system
4) membrane phospholipase- phospholipid
4) membrane phospholipase- phospholipid
system
system

50. Adenylyl cyclase- cAMP second
Adenylyl cyclase- cAMP second
messenger system.
messenger system.
Eg of few hormones acting through this
Eg of few hormones acting through this
system are ;
system are ;
ACTH, CRH, FSH, TSH, PTH, LH,
ACTH, CRH, FSH, TSH, PTH, LH,
VASOPRESSIN (V
VASOPRESSIN (V2
2 receptors) etc.
receptors) etc.

52. Guanyl cyclase-cGMP System-
Guanyl cyclase-cGMP System-
hormones acting through this system
hormones acting through this system
are nitric oxide and ANP.
are nitric oxide and ANP.
Guanylate cyclase produces cGMP from
Guanylate cyclase produces cGMP from
GTP.
GTP.
cGMP exert its response through protein
cGMP exert its response through protein
kinase G, Which when activated initiates
kinase G, Which when activated initiates
cascade of enzyme activation leading to
cascade of enzyme activation leading to
subsequent signaling.
subsequent signaling.

53. membrane phospholipase-
membrane phospholipase-
phospholipid system
phospholipid system
Eg of few hormones acting through this
Eg of few hormones acting through this
system are ;
system are ;
GHRH, TRH, OXYTOCIN,
GHRH, TRH, OXYTOCIN,
VASOPRESSIN (V
VASOPRESSIN (V1
1receptors), GnRH
receptors), GnRH

54. - Hormone bind to receptor in the plasma
Hormone bind to receptor in the plasma
membrane
membrane
- Hormone-receptor complex via G protein
Hormone-receptor complex via G protein
activates membrane enzyme
activates membrane enzyme
phospholipase C.
phospholipase C.
- Activated phospholipase C releases
Activated phospholipase C releases
diacylglycerol(DAG) and inositol
diacylglycerol(DAG) and inositol
triphosphate(IP
triphosphate(IP3
3)
)
- IP
IP3
3 mobilizes calcium from endoplasmic
mobilizes calcium from endoplasmic
reticulum
reticulum

55. - Calcium and DAG together activate
- Calcium and DAG together activate
protein kinase C
protein kinase C
Activated protein kinase C phosphorylates
Activated protein kinase C phosphorylates
proteins and cause specific physiological
proteins and cause specific physiological
action.
action.

57. Calcium-Calmodulin second messenger
Calcium-Calmodulin second messenger
system
system
-Hormone interact with membrane receptors
-Hormone interact with membrane receptors
and opens calcium channels.
and opens calcium channels.
- calcium binds with protein calmodulin which
- calcium binds with protein calmodulin which
has 4 binding site for calcium.
has 4 binding site for calcium.
- calcium binds to 3 sites, calmodulin changes
- calcium binds to 3 sites, calmodulin changes
its shape and causes activation or inhibition of
its shape and causes activation or inhibition of
protein kinases leading to activation or inhibition
protein kinases leading to activation or inhibition
of proteins.
of proteins.

59. 3)
3) Enzyme- linked hormone receptors
Enzyme- linked hormone receptors
Some receptors, when activated act
Some receptors, when activated act
directly as enzymes or are closely
directly as enzymes or are closely
associated with enzymes that they activate.
associated with enzymes that they activate.
These receptors have hormone binding site
These receptors have hormone binding site
on the outside of the membrane and
on the outside of the membrane and
enzyme binding site inside. Eg; Leptin
enzyme binding site inside. Eg; Leptin
receptor, GROWTH hormone etc.
receptor, GROWTH hormone etc.
JAK = Janus tyrosine kinases
JAK = Janus tyrosine kinases
STAT= signal transducer and activator of
STAT= signal transducer and activator of
transcription
transcription

61. Measurements of Hormone conc. in
Measurements of Hormone conc. in
blood
blood
1) Radioimmunoassay ( RIA )
1) Radioimmunoassay ( RIA )
2) Enzyme-linked immunosorbent
2) Enzyme-linked immunosorbent
Assay ( ELISA )
Assay ( ELISA )