The document summarizes the key aspects of the endocrine system. It discusses the two main control systems - the nervous system and the endocrine system. It then focuses on the endocrine system, describing the endocrine glands and hormones. The mechanisms of hormone action and classifications of hormones are explained. Finally, it provides overviews of specific endocrine glands including the pituitary gland, thyroid gland, parathyroid glands, and adrenal glands.

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
Slow control system
Rapid control system

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

4. 2. The endocrine system
hypothalamus

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

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

8. cortex

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

10. GHRH GHIH (SS)
Hypothalamus
PIH
TRH
CRH
Anti-diuretic H.
(ADH)
GnRH
Anterior
pituitary
Growth H.
prolactin H.
Thyrotropin
TSH
Corticotropin
ACTH
posterior
pituitary
FSH & LH
(gonadotropins)
gonads
T3&T4
Thyroid G.
Oxytocin
steroids
Sex H.

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

12. I. Mechanism of action of protein &
polypeptide hormones:
 The hormone (1ry messenger) binds to a cell
membrane receptor of target cell
 formation of a 2nd messenger inside the cell
- cAMP
- Calcium-calmodulin
- DAG & IP3
 changing the activity of certain enzymes

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

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

15. Hormone
(1ry messenger)
3. Membrane
phospholipid system
DAG
(2ry messenger)
Change certain
enzymes activity
IP3

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

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

20. The pituitary gland (hypophysis)

21. GHRH GHIH
(ss)
PIH
TRH
CRH
GnRH
Hypothalamohypophyseal
portal vessels
Adenohypophysis

22. Hypothalamic
neurons
Hypothalamohypophyseal tract

23. Hypothalamus
Anterior pituitary gland hormones
Anterior pituitary gland hormones
 The anterior pituitary produces & secretes
its own hormones
Anti-diuretic H
 Its Hormones are given the extension; (ADH)
tropic, tropin or trophic
posterior
Anterior
pituitary
 It is the master pituitary
for the majority of the
Oxytocin
endocrine glands
Growth H.
prolactin H.
Thyrotropin
TSH
Corticotropin
ACTH
FSH & LH
(gonadotropins)
gonads
T3&T4
Thyroid G.
steroids
Sex H.

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

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

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

27. 3. On carbohydrate metabolism
It increases blood glucose level (diabetogenic
action)
Glycogen
glucose
1
Insulin R. X
Glycogen
synthase
Glucose 6-PO4
2
Glucose
transporter
phosphorylase
Glycolysis
pyruvate

28. 4. On lipid metabolism
GH
Lipolysis
Fat (T.G.)
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. Pituitary infantilism
Failure of:
 Physical
development
 Sexual development
GH
Gonadotropins

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. Hormone
Actions
Deficiency
Pituitary
On bone
dwarfism:
linear
growth (via Only failure
somatomedin) of physical
develop.
Growth  On protein
H.
Anabolic
(Ant.
Pituitary
 On CHO
Pituitary(
infantilism:
Diabetogenic
Failure of
 On lipid
physical &
lipolysis
sexual
develop.
Excess

Gigantism:
Before
closure of
epiphysis
Acromegaly
After
closure of
epiphysis

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. Summary of the actions of ADH
Antidiuretic H.

41. Antidiuretic hormone
Blood volume
Vascular resistance
Arterial blood pressure

42. Regulation of ADH secretion
H2 o
+
ADH- secretion is
increased by
Hypovolaemia
 osmotic pressure of ECF
Baroreceptors
& low pressure volume (e.g. Hge)
 blood R
 Stress
 Drugs (e.g. morphine &
nicotine)
Na+
osmoreceptors

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

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 thyroid follicle cells
From parafollicular
cells
Thyroid Hormones
 T3 (tri-iodothyronine)
 T4 (tetra-iodothyronine,
thyroxine)
Thyrocalcitonin
(calcitonin)
It affects body metabolism
It affects Ca
homeostasis

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

49. mRNA
Physical
mental
Proteins for
growth &
maturation
Sexual
5 Respiration
6 CVS
7 CNS
O2
Enzymes &
transport
ptns
O2 consumption
No of
mitochondria
Metabolic rate 2
substrate
3 GIT
4 Metabolism
blood glucose
blood FFA (lipolysis)
1
Calorigenic
effect

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

51. Disorders of thyroid hormone
secretion
A. Hypothyroidism
In adults
Myxoedema
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

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 2ry messenger

56. Diet 1g
175 mg
8
Extracellular
fluid
1g
10 g
filtered/day
1 Kg
175 mg
99% stable in
1%
exchangable mineralized
bone
in bone fluid

57. Plasma calcium:
Its concentration is about 10mg/dl
1. Ionized 50%
2. Bound to protein 40%
3. Complex & diffusible form 10%
Solubility product:
[Ca2+] x [PO43-] = 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
Ca
hydroxide
Ca
phosphate
B. Osteocyte
C. Osteoclasts
hydroxyapatite

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

60. Osteoblasts
10 mg/dl
Hydroxy
-apatite
crystals
Osteocytes
Bone
fluids
 Ca++
 Ca bound to ptn
 Complex form
Outer surface
of the bone

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

62. 2. On kidney
DCT
PCT
Ca++
+
-
PO4

63. Ca++ reabsorption
Phosphate reabsorption
ECF Ca++
ECF PO43-
Ca++ absorption

64. 2. Vitamin D3
Source: Skin
25-hydroxycholecalcife
rol
1, 25-dihydroxy cholecalciferol
ECF Ca++
ECF PO43-

65. 3. Calcitonin
Source: parafollicular cells
Actions:
1. On Bone (inhibits activity of osteoclats)
2. On kidney
Ca++
-
ECF Ca++
ECF PO43-
PO4

67. Tetany
It is a state of increased neuromuscular excitability
due to decreased ionized calcium
Causes
Hypoparathyroidism
Vitamin D deficiency
Renal disease
Akalemia
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

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

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

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

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

73. 2. physiological Actions
I. Effect on metabolism
1
Gluconeogenesis
a.a.
Glucose
glycogen
Blood
glucose
Blood
FFA
Glycogen
protein
glucose
2
Glycogen
phosphorylase
Lipolysis
synthase
Glucose 6-PO4
Fat (T.G.)
3 Glycolysis
FA Glycerol
pyruvate

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

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

76. Phospholipids
PGs
1
V.D.
 Capillary
permeability

Local redness
Local heat
Local swelling
Lysosomes 2
 White blood cells
Destruction of Local pain
Eosinophils
3
cells
Loss of function
Basophils
Phagocytic cells 4

Fibroblasts
5
Walling off of
infections

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

78. H2O Na+
Aldosterone actions
B. Mineralocorticoids
K+
Actions:
DCT
Collecting
duct
ECFV

79. Disorders of adrenocortical hormones
1.cause:
Cushing’s syndrome
Hypersecretion of cortisol + excess androgen
2. Features
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

81. Addison’s syndrome
1.cause:
Hyposecretion of adrenocortical hormones
2. Features
I. Mineralocorticoid deficiency
1. Hypotension
2. Polyuria & polydipsia
3. Hyperkalemia
Aldosterone H2O
actions
Na+
B. K
Actions
Mineraloco
:
rticoids
ECFV
+

82. II. Glucocorticoid deficiency
1. Metabolism
Depression of many metabolic
functions
- CHO
metabolism
2. Appetite
3. During
stress
4. ACTH
hypoglycemia
Loss of appetite
weight loss
Decreased resistance to stress
ACTH
skin pigmentation

83. Control of glucocorticoid secretion
hypothalamus

85. 1
The Pancreas

87. Actions of insulin
I. On CHO metabolism:
In skeletal m., cardiac m. & adipose tissue
Glycogen
Glycogen
synthase
glucose
phosphorylase
Glucose 6-PO4
Glycolysis
Insulin R.
Glucose
transporter
pyruvate

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

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

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

91. Diabetes mellitus
Organ/tissue Response Blood
urine
Signs &
symptoms
Decreased
glucose
uptake
Hyperg glucos
Polyuria
lycemia
uria dehydration
Glycogenolysis
Gluconeogenesis
Hyperg Osmotic
lycemia diuresis
Protein
catabolism
Polydipsia
Weight loss
Polyphagia
(Hyperphagia)

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

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