The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neural control center for all endocrine systems.

1. PHYSIOLOGY OF
ENDOCRINE SYSTEM
Tonio Ranjitha Amritha N
20-pzo-001
1

2. WHAT IS ENDOCRINE SYSTEM?
 The word endocrine is derived from the Greek terms "endo," meaning
within, and "krine," meaning to separate or secrete
 The endocrine system is a messenger system comprising feedback
loops of the hormones released by internal glands of an organism
directly into the circulatory system, regulating distant target
organs. In vertebrates, the hypothalamus is the neural control
center for all endocrine systems.
 Our endocrine system is made up of several organs called glands.
These glands, located all over your body, create and secrete (release)
hormones.
 Hormones are chemicals that coordinate different functions in your
body by carrying messages through your blood to your organs, skin,
muscles and other tissues. These signals tell your body what to do and
when to do it.
 A hormone is a chemical transmitter. It is released in small amounts
from glands, and is transported in the bloodstream to target organs or
other cells. Hormones are chemical messengers, transferring
information and instructions from one set of cells to another.
2

3. HISTORY
 1841-Friedrich Henle was the first one to recognize “ductless glands,” glands that
secrete their products into the bloodstream and not into specialized ductsIn
 1855 - Claude Bernard distinguished the products of these ductless glands from
other glandular products by the term “internal secretions,” the first suggestion of
what was to become the modern hormone concept.
 1855- Thomas Addison was the first to recognize the disease of adrenal glands that
latter became known as Addison’s disease. He is known as father of endocrinology
 1889 -The first endocrine therapy was attempted by Charles Brown-Séquard, who
used extracts from animal testes to treat male aging. This prompted a vogue in
“organotherapies” that soon faded but that led to adrenal and thyroid extracts that
were the forerunners of modern cortisone and thyroid hormones.
 1902- Ernest Starling andWilliam Bayliss discovered the hormone secretin, which is
produced by the small intestine to trigger the release of pancreatic juices.
 Starling applied the term “hormone” to such chemicals in 1905, proposing a
chemical regulation of physiological processes operating in conjunction with
nervous regulation; this essentially was the beginning of the field of endocrinology.
Claude Bernard
3
Thomas Addison

4. HISTORY
The early years of the 20th century saw the purification of a number of other
hormones, often leading to new therapies for patients affected by hormonal
disorders
1914 - Edward Kendall isolated thyroxine from thyroid extracts
1921- Frederick Banting and Charles Best discovered insulin in pancreatic
extracts, immediately transforming the treatment of diabetes
1921-Romanian scientist Nicolas C. Paulescu independently reported the
presence of a substance called pancrein
1929 -Edward Doisy isolated an estrus-producing hormone from the urine of
pregnant females.
1960- Rosalyn Yalow and S.A. Berson discovered the basis for radio
immunoassays by combining radioactive isotopes with antibodies against
hormones which enable endocrinologists to determine with great precision
minute amounts of hormone, permitting the early diagnosis and treatment of
endocrine disorders.
4
Edward Doisy
Edward Kendall

5. ENDOCRINE GLANDS
Pituitary gland-master gland
Pineal Gland
Thyroid Gland
Parathyroid Gland
Adrenal Gland
Pancreas – Islets of Langerhans
Ovary in Female
Testes in Male
The function of the endocrine system is the
production and regulation of chemical
substances called hormones.
• The endocrine system and nervous system
work together to help maintain homeostasis
balance.
• The hypothalamus is a collection of
specialized cells located in the brain, and is
the primary link between the two systems.
• It produces chemicals that either stimulate
or suppress hormone secretions of the
pituitary gland.
5

6. PITUITARY GLAND
 The pituitary gland, also known as the hypophysis, is a
small, pea-sized gland located at the base of our brains.
 It is referred to as the “master gland” of the human body,
as it releases a variety of hormones that circulate our
system and aid in maintaining our internal homeostasis.
 The term hypophysis (from the Greek for “lying under”)—
another name for the pituitary—refers to the gland’s
position on the underside of the brain.
 The pituitary gland is divided into two distinct lobes: the
anterior (adenohypophysis) and the posterior
(neurohypophysis).

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7. ANTERIOR PITUITARY GLAND
 Anterior PituitaryGland releases 6 hormones they are
1.Thyroid Stimulating Hormone (TSH) Stimulate thyroid gland to
secreteThyroxine hormone and Calcitonin
2.Adrenocorticotropic hormone and corticotropin(ACTH) Stimulate
adrenal gland to produce hormones such as Glucocorticoids Stress
response
3.Folicular Stimulating Hormone and Leutinizing hormone(FSH&LH)
FSH in maleTestosterone
LH in female Progesterone
4 Growth Hormone(GH) Stimulates Metabolism and cell growth
5. Prolactin(PRL) Stimulates Breast Development and secretion of
milk
6.Endorphins opiate receptors in our brains to relieve stress
and pain.
Sexual Characteristics
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8. ROLE OF ANTERIOR PITUITARY HORMONE
 Growth Hormone (GH): essential for the growth and development of bones, muscles, and other
organs. It also enhances protein synthesis, decreases the use of glucose, and promotes fat
destruction.
 Adrenocorticotropin (TRŌ pun) (ACTH): essential for the growth of the adrenal cortex.
 Thyroid-Stimulating Hormone (TSH): essential for the growth and development of the thyroid gland.
 Follicle-Stimulating Hormone (FSH): is a gonadotropic hormone. It stimulates the growth ovarian
follicles in the female and the production of sperm in the male
 Luteinizing Hormone (LH): is a gonadotropic hormone stimulating the development of corpus
luteum in the female ovarian follicles and the production of testosterone in the maleThe yellow
corpus luteum remains after ovulation; it produces estrogen and progesterone.
 Prolactin (PRL): stimulates the development and growth of the mammary glands and milk
production during pregnancy.The sucking motion of the baby stimulates prolactin secretion.
 Melanocyte-stimulating hormone (MSH): regulates skin pigmentation and promotes the deposit of
melanin in the skin after exposure to sunlight
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9. ROLE OF POSTERIOR PITUITARY
HORMONES
 Antidiuretic Hormone (ADH): This hormone have
an effect on Blood Pressure.
 It stimulates the reabsorption of water by the
renal tubules. Hyposecretion of this hormone can
result in diabetes insipidus
 Oxytocin: stimulates the uterus to contract
during labor, delivery, and parturition. A synthetic
version of this hormone, used to induce labor, is
called Pitocin. It also stimulates the mammary
glands to release milk.
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10. PINEAL GLAND
Melatonin: It communicates information about
environmental lighting to various parts of the body.
Has some effect on sleep/awake cycles and other
biological events connected to them, such as a lower
production of gastric secretions at night.
Serotonin: A neurotransmitter that regulates
intestinal movements and affects appetite, mood,
sleep, anger, and metabolism.
The pineal gland is small, pine-cone-shaped which is
about 1 cm in diameter.
Hormones from Pineal Gland
10

11. THYROID GLAND
 T3 and T4 ,Thyroxine hormone plays a vital role in metabolism and regulates the body’s
metabolic processes. It also plays a role in the development and function of nervous system
 It is also essential to BMR – basal metabolic rate (the rate at which a person’s body burns
calories while at rest); influences physical/mental development and growth
 Calcitonin: Regulates Blood Calcium by inhibiting the osteoclast activity. Oesteoclast activity
helps to remove calcium from bone and put into blood and vice versa.
 It prevents excessive absorption in bone by maintaining a healthy calcium ion level in the
blood circulation.
The thyroid gland is a small, butterfly-shaped gland located in the neck, below
the Adam's apple.
Thyroid gland produces 2 hormones, they are thyroxine and calcitonin based on
the presence of cells such as follicle cells and Parafollicular cells
Follicular cells T3 and T4
Parafolllicular cells calcitonin
Role of Hormones
Hyposecretion ofT3 andT4 =
cretinism, myxedema,
Hashimoto’s disease
Hypersecretion ofT3 andT4 =
Grave’s disease, goiter,
Basedow’s disease
Disorders
11

12. PARATHYROID GLAND
Parathyroid gland located in thyroid gland itself.
It is a cluster of small glands located in the posterior side
They secrete parathyroid (PTH) which plays a role in the metabolism of
phosphorus
Drop in blood calcium level triggers the parathyroid gland to release the
hormone.
This hormone target multiple tissues like kidney, Bone, Gut.
Kidney-Direct reabsorption of Calcium
Bone-Causes the reabsorption and resorption of Bone
Gut-Stimulates the conversion ofVitamin D into Calcitrol .This Calcitrol
regulate the absorption of calcium by intestine.
Therefore, It balances and manages the amount of calcium in the blood
as well as in different parts of the body.
Role
Too little production of results in
cramping
Too much synthesis of hormone results
in osteoporosis or kidney stones.
Disorder
12

13. ADRENAL GLAND
It is a triangular-shaped adrenal glands are located on the
top of each kidney.
Composed of outer epithelial cortex and neuronal medulla
region
Zone in cortex and the hormones
released
13

14. SECRETIONS FROM ADRENAL CORTEX
 Corticosterone: It is a steroid hormone influences
potassium and sodium metabolism
 Aldosterone: Essential in regulating electrolyte and water
balance by promoting sodium and chloride retention and
potassium excretion
 Cortisol: Regulates carbohydrate, protein, and fat
metabolism. It has an anti-inflammatory effect. It helps
the body cope during times of stress. It also maintains
immune system.
 Hypo secretion of these hormones results in Addison’s
disease and hypersecretion results in Cushing’s disease
 Androgens: Stimulates the synthesis of several hormone
in early puberty and in secondary sexual charcateristics.
14

15. SECRETIONS FROM ADRENAL MEDULLA
 In medulla region Catecholamines such as epinephrine and nephrine hormones are secreted .It also
secrete peptide hormones such as Somatostatin and substance B- which plays a role of inhibition.
 Epinephrine is also called adrenalin-It elevates systolic blood pressure, increases heart rate and cardiac
output, speeds up the release of glucose from the liver giving a spurt of energy. It dilates the bronchial
tubes and relaxes airways, dilates the pupils to see more clearly. It is often used to counteract an allergic
reaction.
 Norepinephrine- like epinephrine, is released when the body is under stress. It creates the
underlying influence in the fight or flight response. As a drug, however, it actually triggers a drop
in heart rate.
Catecholamines
Epinephrine
Non-Epinephrine
15

16. PANCREAS
 The islets of Langerhans are small clusters of cells located in the pancreas.
 Alpha cells secretes glucagon which facilitate the breakdown of glycogen
to glucose.This elevates the blood sugar. It also produces ketone
 Beta cells secretes the hormone insulin which is essential for the
maintenance of normal blood sugar levels. Insulin –Lowers the level of
blood glucose by uptake of glucose by all other cells
 It converts the glucose and store it in the liver also involved in triglyceride by
adipose tissue of the body
 Inadequate levels result in diabetes mellitus
 Delta cells secretes somatostatin which suppress the release of glucagon
and insulin. Regulate the carbohydrate metabolism
Two types
Exocrine
Endocrine
Digestive Juices
Helps to digest
protein and fat
Hormones
1.Insulin
2.Glucagon
16

17. OVARY GLAND HORMONE
 Ovary glands present in females.The ovaries produce several steroid
hormones such estroge0n hormones and progesterone and
another protein type of hormone, inhibin for the role of inhibition
 These hormones prepare the uterus for pregnancy, promote the
development of mammary glands, play a role in sex drive, and
develop secondary sex characteristics in the female.
 Estrogen plays it’s role in egg development and in the process of
ovulation.The egg development takes place in follicle. It also
helps in the process of maturation of ovary and follicle
 It is essential for the growth, development, and maintenance of
female sex organs
 Progesterone is important after the ovulation proves onlt.it
maintains the integrity of the imperial line and also act very well in
pregnancy and maintain the condition.
 So after the implantation of egg it can grow and develop into a
proper employer.
 Inhibin-Regulates the secretion of Follicular Stimulating
hormones.
17

18. TESTIS HORMONE
 The testes produce the male sex
hormone called testosterone.
 It is essential for normal growth and
development of the male sex organs.
 It play a key role in Production and
Maturation of Sperm Cells.
 It is responsible for Secondary Sexual
Characteristics.
 It also controls libido
18

19. ENDOCRINE SYSTEM-OVERVIEW
19

20. HYPOTHALAMUS
Role of Hypothalamus
Hypothalamus has Cluster of neurons that secrete
different types of Neuro hormones into the circulation of
Blood.
Different Regions of Hypothalamus are Para ventricular
and Supraoptic secretes the hormones into the posterior
pituitary
Inhibiting Hormones –Somatostatin-Required for inhibiting
the growth by pituitary
Dopamine-Converts into prolalctin Inhibiting hormone.
In general, Dopamine is used to treat shock. It dilates the
arteries, elevates systolic blood pressure, increases cardiac
output, and increases urinary output.
20

21. ENDOCRINETISSUES OR OTHER GLAND
THAT PRODUCETHESE ENZYMES.
 During pregnancy, the placenta serves as an endocrine gland. It produces
chorionic gonadotrophin hormone, estrogen, progesterone.
 The mucosa of the pyloric area of the stomach secretes the hormone
gastrin(peptide hormone), which stimulates the production of Hcl inorder
to maintain the acidic medium which further produce another hormone
pepsin for digestion.
 Secretin –Gall bladder and pancreas to produce bicarbonate ion. It
neutralizes the Acidic Environment in the stomach. Activity of Secretin
near the Dudoneum helps in neutralizing the Acid.

Cholocystekin(CCK) -Stimulates the secretion of Bile salts from
gallbladder-Emulsification of fat
 Gastric inhibitory polypeptide (GIP)-Stimulates the Pancreas to uptake of
glucose level in the blood stream
21

22. ENDOCRINETISSUES OR OTHER GLAND
THAT PRODUCETHESE ENZYMES
 Motiline-Release every 90 minutes. It causes peristaltic waves
which aids in the movement of food till the terminal of intestine.
 KidneyTissue secretes Erythropoitic hormone which causes bone
marrow to produce new cells.
 Calciterol produced in kidney which is the active form of vitamin D
in response to parathyroid hormones convert D into D3(act as
calcitriol).It Helps in the Reabsorption of Calcium Intestine.
 Heart SpecialiseCell secrete Atrial Natriuretic hormone which
causes kidney to excrete excess amount of sodium to regulate the
blood pressure are blood volume
 The thymus gland has two lobes, and is part of the lymphatic
system. It is a ductless gland, and secretes thymosin.This is
necessary for theThymus’ normal production ofT cells for
the immune system.
22

23. HORMONE BIOCHEMISTRY AND
SECRETION
 Peptide Hormone-Chain of Amino Acid with 3 to 20 amino groups. It is water
soluble Eg. Oxytocin
 Protein Hormone –Large chain of Amino Acid which is more than 20 amino
groups. Eg. Growth Hormone(GH), Insulin.
 Amine Hormones contain Amino acid in most cases tyrosine
Eg. 1. Catecholamines- Epinephrine, Non epinephrine and dopamine- Water
Soluble
2.Thyroid Hormone-Little bit soluble
 Steroid hormone-Derived From Cholesterol. Eg.-Testosterone and Progesterone.
These hormones are hydrophobic ; only OH present regions are Hydrophilic.
23

24. CONTROL OF HORMONE SECRETION/MODE OF
REGULATION OF HORMONES
 Hormones can be controlled by 3 ways:
1.Neural Control
2.Hormonal
Control
3.Humoral
Control
Neural-It occurs in
Adrenal Gland ,directly
stimulated by symphatic
Nervous system
Eg.-Epinephrine and non
epinephrine-Reinforce
the actions of
symphateric nervous
system
Hormonal-Hormones of
one endocrine gland
stimulates the secretion
of hormones at other
gland –Hormone
cascades.
Hormones secretion is
much controlled by
hypothalamus
Humoral –This mode occurs when the substances other than the hormones that controls the secretion of
Endocrine glands.
For eg.-Insulin secretion by pancreas is to determine with multiple factors. It is not only determined by the
concentration of insulin but also but also rise in Glucose level after a meal .
Factors-Concentration of Glucose-Production of Insulin
24

25. HPA AXIS -THE HYPOTHALAMIC–
PITUITARY–ADRENAL AXIS
The HPA axis is responsible for the
neuroendocrine adaptation component
of the stress response.This response is
characterized by hypothalamic release
of corticotropin-releasing factor (CRF).
CRF is also known as CRH or
corticotropin-releasing hormone
A major component of the homeostatic
response is the hypothalamic-pituitary-
adrenal (HPA) axis, an intricate, yet
robust, neuroendocrine mechanism that
mediates the effects of stressors by
regulating numerous physiological
processes, such as metabolism, immune
responses, and the autonomic nervous
system (ANS).
25

26. HPA AXIS
26

27. HORMONAL ACTIVITY AND MODE OF
ACTION
1.Direct Gene Activation
Hormone
Nucleus
Transcriptional factor
 Hormones are activated by 2 ways
2.Second Messenger System
Hormones binds to receptor
Further activates
Sympathetic nervous system
Establish Jobs
More protein
Transcriptional Factor(TF)
Cell responds to this stimuli in
several different ways, they are
1) Cause contraction of Muscle
Tissue
2) Secretion of cellular Products.
3) Effecting of ion exchange through
channels
4) Cause Synthesis of new peptides
and proteins
5) Cause Break down of Storage
Molecules
27

28. HORMONE RECEPTORS AND MECHANISMS
OF ACTION
ForWater
Soluble
Hormones
28

29. HORMONE RECEPTORS AND MECHANISMS OF
ACTION
For Fat Soluble
Hormones
29

30. MECHANISM OF HORMONES
30

31. CONCLUSION
 Therefore, Endocrine gland is an important gland that helps in homeostasis
balance .
 Each gland Secrete different types of hormones which has it’s own unique role
helps in the physiology of Endocrine system.
 Defect in one hormone synthesis pattern will also cause great impact to our
human system. So it’s need necessary to have a check on hormone balance too if
are unwell.
31

32. It‘s Quiz time
32

33. False.
True.
Pineal Gland is called
as the master Gland ?
33
Answer: False
Pituitary Gland is
called as the master
gland

34. Edward Doisy
e.
William Havery
d.
Thomas Addison
c.
Louie Pastuer
b.
Starling
a.
Who is the father of Endocrinology?
34
Answer: Option C

35. Peptide Hormone
d.
Steroid hormone
c.
Iodothyronine hormone
b.
Amine Hormone
a.
Oxytoicn hormones comes under which type of hormones?
Answer: Option D

36. False.
True.
Catecholamine are
Secreted by Adrenal
Medulla ?
Answer:True

37. Melatonin
e.
Somatostatin
d.
Cortisol
c.
Glucagon
b.
Insulin
a.
Alpha Cells in the Pancreas secrete which hormone ?
Answer: Option B

38. TO KNOW MORE ABOUT CONCEPT
 1.Endocrinology Receptor Pathways
 https://www.youtube.com/watch?v=RMV130vU8gA
 2.Human Endocrine System
 https://www.youtube.com/watch?v=YcPicFL5Jnw
 https://www.youtube.com/watch?v=BenVSmBG7wU
 https://www.youtube.com/watch?v=Sju104tYFW8
 https://www.youtube.com/watch?v=7t9b-l0nJNc&t=33s
 3.HPA axis and Stress Response
 https://www.youtube.com/watch?v=wQJJQ3EcDtw
38

39. SUMMARY
39

40. REFERENCE
 Endocrine system physiology | human endocrine hormones-
https://www.youtube.com/watch?v=T6mPS53Jb1M&t=7215s
 https://www.britannica.com/science/endocrinology
 Guyton and HallTextbook of medical physiology 12th edition - John E. Hall,Pg 5-7;715-
787;881-1016
 Basics of Medical Physiology-4th edition - DVenkatesh and HH Sudhakar ,513-563
 https://www.brainkart.com/article/Hormone-Receptors-and-Mechanisms-of-Action_21855/
 https://accessmedicine.mhmedical.com/
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