Endocrine System - Physiology

1. “The endocrine system”
By

Dr. Mary A. Youssef

________________________________
Cairo University
2012

2. Two main control systems
1. The nervous system
2. The endocrine system
Rapid control system
Slow control system

3. Exocrine glands Endocrine glands
Have ducts ductless
Secrete their products to
the outer surface or the
lumen of GIT
Secrete their products
(hormones) into the
blood
Can not Can reach distant tissue

4. 2. The endocrine system
hypothalamus

6. Gland
Hormone
(Sender)
(signal)
blood
receptor
(receiver &
transducer)
Hormone
Target cell
 Small amount
 Rate of secretion
 Superadded
rhythms
 Effector
 Opposing effects

7. Classification of hormones
1. According to their chemical nature
olypeptide H.protein and P. 1
Hypothalamic, pituitary, pancreatic &
parathyroid H.
. Steroid H.2
Adrenocortical and gonadal H.
. Hormones derived from a.a.3
Thyroid h. & adrenal medullary h.

8. cortex

9. 2. According to their origin
Hypophysiotropic hormones
1. Releasing H.
GHRH
Thyrotropin (TSH) RH (TRH)
Corticotropin RH
Gonadotropin RH
2. Inhibiting H.
Somatostatin (SS)
Prolactin inhibiting H.
Hypothalamus

10. Hypothalamus
Anterior
pituitary
posterior
pituitary
prolactin H.
Thyrotropin
TSH
Thyroid G.
T
3&T
4
Growth H.
Corticotropin
ACTH
steroids

FSH & LH
(gonadotropins)
gonads
Sex H.

Anti-diuretic H.
(ADH)
Oxytocin
GHIH (SS) GHRH
PIH
TRH
CRH
GnRH

11. Mechanisms of hormone action
What is meant by a target cell?
GH
What are the target cells
of GHRH?
a. cells of the Hypothalamus
b. Anterior pituitary cells
c. Posterior pituitary cells
d. Bone cells

12. I. Mechanism of action of protein &
polypeptide hormones:
 The hormone (1
ry
messenger) binds to a cell
membrane receptor of target cell
 formation of a 2
nd
messenger inside the cell



 changing the activity of certain enzymes
- cAMP
- Calcium-calmodulin
- DAG & IP
3

13. Hormone
(1
ry
messenger)
Receptor
1. cAMP system
Change certain
enzymes activity
(2
ry
messenger)

14. 2. Calcium-calmodulin
system
Change certain
enzymes activity
Hormone
(1
ry
messenger)
(2
ry
messenger)
calmodulin

15. 3. Membrane
phospholipid system
DAG
IP
3
Hormone
(1
ry
messenger)
Change certain
enzymes activity
(2
ry
messenger)

16. II. Mechanism of action of Steroid H.
Receptor
Increase or a decrease in the synthesis
of a certain protein

17. III. Mechanism of action of Thyroid H.
T
T
T
T
T
T
Receptor
Increase in the synthesis of certain proteins in almost all cells

18. H. derived from
a.a.
Steroid H.
Protein or
polypeptide H.
Nuclear R. Cytoplasmic R.
Cell membrane
R.
_ _
2ry messenger
- cAMP
-Ca-calmodulin
-DAG & IP3
Synthesis of
new proteins
Synthesis of
new proteins
Change the
activity of
already present
enzymes
Thyroid &
adrenal
medullary h.
Adrenocortical
& Gonadal h.
Hypothalamic,
pituitary,
parathyroid,
pancreatic

19. Regulation of hormone secretion
Target gland
Hypothalamus
Ant. Pituitary G.
Target gland hormone
Substrate Mineral
Mineral-
hormone
feedback
Substrate-
hormone
feedback
Hormone
-hormone
feedback

20. The pituitary gland (hypophysis)

21. Hypothalamo-
hypophyseal
portal vessels
GHIH
(ss)
GHRH
PIH
TRH
CRH
GnRH
Adenohypophysis

22. Hypothalamic
neurons
Hypothalamo-
hypophyseal tract

23. Anterior pituitary gland hormones
 The anterior pituitary produces & secretes
its own hormones
 Its Hormones are given the extension;
tropic, tropin or trophic
 It is the master for the majority of the
endocrine glands



Hypothalamus
Anterior
pituitary
posterior
pituitary
prolactin H.
Thyrotropin
TSH
Thyroid G.
T
3&T
4
Growth H.
Corticotropin
ACTH
steroids

FSH & LH
(gonadotropins)
gonads
Sex H.

Anti-diuretic H.
(ADH)
Oxytocin
Anterior pituitary gland hormones

24. Which of these is not produced by
the anterior pituitary?
►ACTH
►follicle-stimulating hormone (FSH)
►Somatostatin (ss)
►Somatotropic H.

25. Growth hormone
(somatotropic hormone)
It is a protein hormone that stimulates growth
1. On bone growth
Actions of growth hormone
GH
somatomedin

26. 2. On protein metabolism
It is an anabolic hormone
mRNA
a.a. a.a
.
1. Rate of DNA
transcription
2. a.a. transport into the
cell

27. 3. On carbohydrate metabolism
It increases blood glucose level (diabetogenic
action)
glucose
Glucose 6-PO
4
Glycogen

Glycogen
synthase
phosphorylase
Insulin R.
Glucose
transporter pyruvate
2
X Glycolysis
1

28. 4. On lipid metabolism
Fat (T.G.)
GH Lipolysis
FA Glycerol
FFA

29. Factors affecting GH secretion
GH secretion is
increased by
GHRH
 Low blood glucose
and FFA
 Protein meal
 Emotional stress
 Deep sleep
GH secretion is
Decreased by
somatostatin
 High blood glucose
and FFA
 treatment with
corticosteroids

30. Disorders of GH secretion
A. Growth hormone deficiency (dwarfism)
 Decrease in
the size of the
trunk &
extremities
 Normal
mental &
sexual
development

31. GH
Gonadotropins
Pituitary infantilism
Failure of:
 Physical
development
 Sexual development

32. B. Growth hormone Excess
 Before closure of epiphyses Gigantism
taller than normal
 After closure of epiphysis Acromegaly

33. Main features
of acromegaly
No linear growth
of bones
1.Bones of hands
and feet
2.Bones of the face
3.Mandible
4.The spine
5.Diabetes

34. Excess Deficiency Actions Hormone
:Gigantism
Before
closure of
epiphysis

Acromegaly
After
closure of
epiphysis
Pituitary
dwarfism:
Only failure
of physical
develop.

Pituitary
infantilism:
Failure of
physical &
sexual
develop.
On bone
linear
growth (via
somatomedin)
On protein
Anabolic
On CHO
Diabetogenic
On lipid
lipolysis

Growth
H.
(Ant.
(Pituitary

35. Growth hormone
A. directly stimulates growth of cartilage
and bone.
B. enhances protein breakdown in nonvital
muscles.
C. levels are subnormal in Gigantism.
D. promotes lipolysis in adipose tissue.

36. Posterior pituitary gland hormones

37. Antidiuretic hormone (ADH)
(Vasopressin)
 It is a protein hormone
 Formed in supraoptic n. of the
hypothalamus and secreted from the
posterior pituitary

38. Actions of ADH (vasopressin)
1. On Kidney
Anti-diuresis (retention of water)

39. 2. On blood vessels
Pressor effect
3. On smooth muscles
Contraction of the smooth muscles

40. Antidiuretic H.
Summary of the actions of ADH

41. Antidiuretic hormone
Blood volume Vascular resistance
Arterial blood pressure

42. Regulation of ADH secretion
ADH secretion is
increased by
 osmotic pressure of ECF
 blood volume (e.g. Hge)
 Stress
 Drugs (e.g. morphine &
nicotine)
osmoreceptors
H
2o
Na
+
+
-
Baroreceptors
& low pressure R
Hypovolaemia

43. Disorders of ADH secretion
ADH deficiency
Diabetes insipidus
1. Polyuria
2. Polydipsia
3. Loss of water
soluble vitamins

44. Oxytocin
 It is a protein hormone
 Formed in paraventricular n. of the
hypothalamus and secreted from the
posterior pituitary
Actions of Oxytocin
1.Uterine contraction during delivery
2.Milk ejection action during suckling
3.Mild antidiuretic action

45. The Thyroid gland

46. Histology
1.Follicles
 Lined with a
single layer of
epithelial cells
 Its centre is filled
with colloid
2. Parafollicular
cells

47. Hormones secreted from the thyroid gland
From parafollicular
cells
From thyroid follicle cells
Thyrocalcitonin
(calcitonin)
Thyroid Hormones
 T
3 (tri-iodothyronine)
 T
4 (tetra-iodothyronine,
thyroxine)
It affects Ca
homeostasis
It affects body metabolism

48. Actions of Thyroid hormones
T
T
T
T
T
T
Synthesis of
new protein
Receptor

49. mRNA
Proteins for
growth &
maturation
Enzymes &
transport
ptns
of oN
mitochondria
O
2
substrate
GIT
Metabolism
Calorigenic
effect
2
3
4
5 Respiration
1
6 CVS
blood glucose
blood FFA (lipolysis) CNS
7
Physical
mental
Sexual
O
2 consumption
Metabolic rate

50. Regulation of thyroid hormones
Thyroid h. secretion is regulated by :
1. TRH
2. TSH
3. Feedback
Mechanism
4. Cold
5. Stress
Ant.
pituitary
Hypothalamus
Thyroid
++
--
--
Cold &
emotional
stress
+
Iodine
deficiency
++

51. Disorders of thyroid hormone
secretion
A. Hypothyroidism
1. BMR & calorigenesis
2.Generalized decrease in activity of all body
systems
3.Myxoedematous tissue
CVS: Heart rate & Cardiac output
GIT: intestinal motility (constipation)
CNS: slow mentation & sluggish reactions, S
In adults Myxoedema

52. Since birth Cretinism
Delayed physically: Dwarf, teeth erupt later
than normal
Delayed mentally
Delayed sexually
Special features:
 Depressed nasal bridge
 Wide nostrils
 Protruding tongue
 Protuberant abdomen

53. B. Hyperthyroidism (thyrotoxicosis)
One of its types is Grave’s disease (exophthalmic
goitre)
Autoimmune disease
TSH-R(stim) Ab
TSH-R
(stim) Ab

54. Characters of hyperthyroidism
1. BMR & calorigenesis
2.Generalized increase in activity of all body
systems
3.Loss of weight in spite of increased food
intake
CVS: Heart rate & Cardiac output
GIT: intestinal motility (diarrhea)
CNS: tremors, irritability, insomnia

55. Calcium homeostasis
 The adult human body contains 1 Kg of calcium
 Functions of calcium:
1.Mineralization of bones & teeth
2.Blood clotting
3.Neuromuscular excitability
4.Muscle contraction & relaxation
5.Release of neurotransmitters
6.Hormonal secretion & act as a 2
ry
messenger

56. 8



Diet 1g
Extracellular
fluid
1g
175 mg
1 Kg
1%
exchangable
in bone fluid
99% stable in
mineralized
bone
10 g
filtered/day
175 mg

57. Plasma calcium:
Its concentration is about 10mg/dl
1. Ionized 50%
2. Bound to protein 40%
3. Complex & diffusible form 10%
Solubility product:
[Ca
2+
] x [PO
4
3-
] = constant

58. Bone
Bone tissue is formed of:
1. Organic matrix (formed mainly of collagen)
2. Crystalline salts (mainly hydroxyapatite
crystals & calcium phosphate)
3. Bone cells
A. Osteoblast
B. Osteocyte
C. Osteoclasts
Ca
hydroxide
Ca
phosphate
hydroxyapatite

59.  Bone matrix
proteins
 Alkaline
phosphatase
Bone
forming
cells
Secrete
 H
+
that
dissolve
hydroxyapatite
Acid protease
that dissolve
collagen
Bone
eating
cells
Secrete
Phosphate
ester
phosphate
Ca
phosphate

60. Outer surface
of the bone
Osteoblasts
Osteocytes
10 mg/dl

 Ca
++
 Ca bound to ptn
 Complex form
Bone
fluids
Hydroxy
-apatite
crystals

61. Hormonal control of plasma Ca level
3 hormones play a role in the control of plasma Ca
level
1. Parathormone hormone (PTH)
: Parathyroid glandSource
:Actions
1. On bones
A.Rapid phase
B.Slow Phase
2. On kidney
3. On GIT
PTH
Ca
++

Ca
++

Ca
++

Ca
++

Ca
++

Hydroxyapatite
crystals
Ca
++

62. 2. On kidney
PCT
DCT Ca
++
PO
4
+
-

63. Ca
++
reabsorption
Phosphate reabsorption
Ca
++
absorption
ECF Ca
++
ECF PO
4
3-

64. 3. Vitamin D2

Skin Source:
25-hydroxy-
cholecalcife
rol
1, 25-dihydroxy cholecalciferol
ECF Ca
++
ECF PO
4
3-

65. . Calcitonin3
: parafollicular cellsSource
:Actions
1. On Bone (inhibits activity of osteoclats)
2. On kidney
ECF Ca
++
ECF PO
4
3-
Ca
++
PO
4
-
-

67. Tetany
It is a state of increased neuromuscular excitability
due to decreased ionized calcium
Causes
Types:
Latent tetany: when the total plasma Ca is
between 9 and 7 mg/dl. Its manifestations do
not appear during rest
Manifest tetany: when the total plasma Ca

drops below 7mg%. The patient is presented
by spasmodic contractions
Hypoparathyroidism
Vitamin D deficiency
Renal disease
Akalemia

68. The adrenal glands
Each adrenal gland consists of two
endocrine organs
1. Adrenal cortex
 Secretes steroid hormones
2. Adrenal medulla
 Secretes catecholamines
cortex

69. Cortex

Medulla

Zona
glomerulosa
Zona
Fasciculata
Zona Reticularis
Mineralocorticoids
Glucocorticoids
Sex Hormones
Aldosterone
cortisol
Androgens & estrogen

70. A. Glucocorticoids
 Cortisol = 95% of total glucocorticoid
activity.

71. Actions of cortisol depends on its plasma
level:
1. Permissive Actions
2. Physiological Actions
3. Pharmacological Actions
its presence even at small amounts
permits certain processes to occur
Effects of the normally present hormone
levels in plasma
Effects of the high levels of hormone in
plasma

72. It means that cortisol does not initiate the
changes, but its presence even at small
amounts permits certain processes
1. Permissive Actions
Glucagon &
catecholamines
Glycogenolysis
Catecholamines
Arteriolar V.C.
response &
bronchodilatation

73. 2. physiological Actions
I. Effect on metabolism
Glucose
Gluconeogenesis
glycogen
glucose Glucose 6-PO
4
Glycogen
Glycogen
synthase
phosphorylase
pyruvate
3
Glycolysis
2
Blood
glucose
protein
Fat (T.G.)
Lipolysis
FA Glycerol
Blood
FFA
1
a.a.

74. II. Effect on CNS
Required for normal EEG pattern
III. Weak mineralocorticoid effect
IV. Anti-stress effect
I. Effect on metabolism
V.C.
catecholamines
Permissive action
Blood glucose
Plasma a.a.
Plasma FFA

75. 3. pharmacological Actions
I. Anti-allergic effect
II. Anti-inflammatory effect
Mast cell

76. Local redness
Local heat
Local swelling
 V.D.
 Capillary
permeability
Phospholipids

PGs
Local pain
Loss of function
Destruction of
cells
 Lysosomes
 White blood cells
Eosinophils
Basophils
Phagocytic cells
Walling off of
infections
Fibroblasts
1
2
3
4
5

77. Control of glucocorticoid secretion
1
2
3
4
5
hypothalamus

78. B. Mineralocorticoids
Actions:
DCT
Collecting
duct
Na
+
K
+
Aldosterone actions H
2O
ECFV

79. Cushing’s syndrome
1.cause:
Hypersecretion of cortisol + excess androgen
. Features2
I. Excess cortisol
1.CHO metabolism (DM)
2.Excess protein catabolism
3.Disturbed fat deposition

II. Mineralocorticoid effect
III. Excess Androgens
 Moon face
 Buffalo hump
 Purple striae
Disorders of adrenocortical hormones

81. Addison’s syndrome
1.cause:
Hyposecretion of adrenocortical hormones
. Features2
I. Mineralocorticoid deficiency
1. Hypotension
2. Polyuria & polydipsia
3. Hyperkalemia

B.
Mineraloco
rticoids
Actions
:
Na
+
K
+
Aldosterone
actions
H
2O
ECFV

82. II. Glucocorticoid deficiency
Depression of many metabolic
functions

hypoglycemia
1. Metabolism

- CHO
metabolism
Decreased resistance to stress 3. During
stress
ACTH skin pigmentation 4. ACTH
Loss of appetite weight loss 2. Appetite

83. Control of glucocorticoid secretion
hypothalamus

85. 1



The Pancreas

87. Actions of insulin
I. On CHO metabolism:
glucose
Glucose 6-PO
4
Glycogen

Glycogen
synthase
phosphorylase
Insulin R.
Glucose
transporter pyruvate
Glycolysis
 In skeletal m., cardiac m. & adipose tissue

88. Glucose
Glucose
Glucose 6 P
+
Glycogen
Glycogenesis +
Glycogenolysis
-
gluconeogensis -
1. Indirectly
facilitates
glucose entery
2. Promotes
glycogenesis
3. Inhibits
glycogenolysis
4. Inhibits
gluconeogensis
 In the liver

89. II. On lipid metabolism: lipogenesis
III. On protein metabolism: (Anabolic)
mRNA
a.a. a.a
.
1. Rate of DNA
transcription
2. a.a. transport into the
cell
IV. On Growth

90. Actions of Glucagon
Glucagon Insulin
glycogenolysis
gluconeogenesis
glycogenolysis
gluconeogenesis
On CHO
metabolism
Lipolysis Lipogenesis
On lipid
metabolism
Catabolic Anabolic
On protein
metabolism
hypoglycemia hyperglycemia Stimulus

91. Diabetes mellitus
Signs &
symptoms
urine Blood Response Organ/tissue
Polyuria
dehydration
glucos
uria
Hyperg
lycemia
Decreased
glucose
uptake
Polydipsia Osmotic
diuresis
Hyperg
lycemia

Glycogenolysis
Gluconeo-
genesis
Weight loss
Polyphagia
(Hyperphagia)
Protein
catabolism

92. Glucose Homeostasis
 The importance to maintain a normal blood
glucose concentration
 Body response to ingestion of a meal (high
glucose)
100
120
140
1h 2h 3h 4h
Insulin returns blood glucose
level back to control level

93. Mechanisms controlling blood
glucose concentration
1. Glucostatic function of the liver
Glycogenesis (after meals)
Glycogenolysis (between meals)
Gluconeogenesis (during fasting)
2. Hormonal Mechanism
Both insulin & glucagon function as important
feedback control systems to maintain a normal
blood glucose level

94. Thank You