endocrine system

1. The Endocrine
System
Nikita Kale
Alard College of Pharmacy, Pune

2. 2
Overview of the Endocrine System
 System of ductless glands that secrete
hormones
 Hormones are “messenger molecules”
 Circulate in the blood
 Act on distant target cells
 Target cells respond to the hormones for which they
have receptors
 Hormones are just molecular triggers
 Basic categories of hormones
 Amino acid based: modified amino acids (or amines),
peptides (short chains of amino acids), and proteins
(long chains of amino acids)
 Steroids: lipid molecules derived from cholesterol

3. 3
Endocrine Organs
 Purely endocrine organs
 Pituitary gland
 Pineal gland
 Thyroid gland
 Parathyroid glands
 Adrenal: 2 glands
 Cortex
 Medulla
 Endocrine cells in other
organs
 Pancreas
 Thymus
 Gonads
 Hypothalamus

4. 4
Mechanisms
of hormone
release
(a) Humoral: in response to changing
levels of ions or nutrients in the blood
(b) Neural: stimulation by nerves
(c) Hormonal: stimulation received from
other hormones

5. 5
Pituitary__________
(hypophysis)
Hypothalamus___________
Hypothalamus__
Anterior pituitary__
(adenohypophysis)
_____________Posterior pituitary
(neurohypophysis)
Learn the 3 endocrine organs on this slide:
Hypothalamus
Pituitary (hyophysis)
Pineal

6. Pituitary gland
 It is also known as hypophysis
 It is small pea shaped gland, measuring about 1 gm in
weight.
 It lies in bony cavity at the base of brain known as Sella
Turcica.
 Pituitary gland is connected to hypothalamus by
hypophysial stalk known as infundibulum or pituitary
stalk.
 It is divided into 2 parts –
Adenohypohysis or anterior pituitary (75%)
Neurohypohysis or posterior pituitary (25%)
 It is divided by small avascular zone called pars
intermedia.
 Pituitary gland is slightly larger in females than in males.
6

7. Adenohypophysis-
 It is made up of 5 different types of cells.
 These cells are responsible for production of 7
major hormones secreted by pituitary gland.
 These 5 types of cells are-
Somatotrophs
Corticotrophs
Thyrotrophs
Gonadotrophs
Lactotrophs
7

8. 8
Two divisions:
 Anterior pituitary
(adenohypophysis)
 Posterior pituitary
(neurohypophysis)
Sits in hypophyseal fossa: depression in sella turcica of
sphenoid bone
Pituitary secretes 9 hormones
The Pituitary
1. TSH
2. ACTH
3. FSH
4. LH
5. GH
6. PRL
7. MSH
8. ADH (antidiuretic hormone), or vasopressin
9. Oxytocin
_________________________________________________________________
The first four are “tropic”
hormones, they regulate the
function of other hormones
________

9. 9
What the letters stand for…
 TSH: thyroid-stimulating hormone
 ACTH: adrenocorticotropic hormone
 FSH: follicle-stimulating hormone
 LH: luteinizing hormone
 GH: growth hormone
 PRL: prolactin
 MSH: melanocyte-stimulating hormone
 ADH: antidiuretic hormone
 Oxytocin

10. 10
Hypothalamus controls anterior pituitary by 2 hormones
 Releasing hormones (releasing factors)
Secreted like neurotransmitters from neuronal axons
into capillaries and veins to anterior pituitary
(adenohypophysis)
TRH-----turns on TSH
CRH-----turns on ACTH
GnRH (=LHRH)---turns on FSH and LH
PRF-----turns on PRL
GHRH----turns on GH
 Inhibiting hormones
PIF-----turns off PRL
GH inhibiting hormone ---turns off GH
Hypothalamus control posterior pituitary by nerve signals

11. 11
What the letters mean…
 Releasing hormones (releasing factors) of hypothalamus
Secreted like neurotransmitters from neuronal axons into capillaries
and veins to anterior pituitary (adenohypophysis)
TRH (thyroid releasing hormone) -----turns on* TSH
CRH (corticotropin releasing hormone) -----turns on ACTH
GnRH (gonadotropin releasing hormone) ---turns on FSH and
LH
PRF (prolactin releasing hormone) -----turns on PRL
GHRH (growth hormone releasing hormone) ----turns on GH
 Inhibiting hormones of hypothalmus
PIF (prolactin inhibiting factor) -----turns off PRL
GH (growth hormone) inhibiting hormone ---turns off GH
These hormones are secreted within the hypothalamus
itself and are brought to the anterior pituitary through
minute blood vessels called hypothalamic hypophysial
portal vessels.
*Note: “turns on” means causes to be released

12. 12
So what do the Anterior Pituitary Hormones do?
 Somatotrophs- 30-40% cells of adenohypophysis are
somatotrophs. release hGH- causes growth of cells and
tissues and regulate metabolism. It typically stimulates
liver, muscle, cartilage, bone, and other tissue to
synthesise and secrete insulin like growth factor (IGFs).
 These (IGFs) promote of body cells, protein anabolism,
tissue repair, lipolysis, and elevation of blood glucose
level.
 Control through- GHRH; GHIH
 Thyrotrophs- (5%) release TSH which causes to secrete
thyroxine and triiodothyronine.
 Control through- TRH; GHIH

13. `
 Corticotrophs- (20%)release 2 basic hormone
ACTH and MSH. ACTH stimulates the
adrenal cortex to produce corticosteroids:
aldosterone and cortisol(glucocorticoids).
MSH stimulates dispersion of melanin in
melanocytes.
 Control through- CRH; dopamine.
 Gonadotrophs- (4-5%) secretes two powerful
hormone FSH and LH(interstitial cell stimulating
hormone). These two hormones are secreted in
both male and female but have different role.
13

14.  FSHfemale stimulates follicle growth and
ovary to produce estrogen;
FSHmalestimulates sperm production by
testes.
 LHfemalesecretion of estrogen and
progesterone and promotes ovulation and
formation of corpus luteum.
 LHmalestimulates interstitial cell in testes
to produce and develop testosterone.
 These 2 hormones are responsible for
development and maturity of gonads.
14

15.  Lactotrophs- (3-5 %) secrete prolactin
which promotes development of breast
and milk secretion of mammary glands.
15

16. Functions of hGH
It is also known as somatotropin or
somatotropic growth hormone.
 Increase protein synthesis in cells.
 Decreased protein breakdown
 Stimulates lipolysis in adipose tissue.
 Increases utilisation of free fatty acid for
energy.
 Decreased rate of glucose utilisation.
 Fats are maximally used for production of
energy, amino acids proteins and promotes
growth. 16

17. Disorders related hGH
 Hyposecretion dwarfisim in childhood
 panhypopituitarism in adulthood.
 Hypersecretion giantism/gigantism in
childhood
 acromegaly in adulthood
17

18. 18
Posterior Pituitary (Neurohypophysis)
 Neurohypophysis is made up of cells called
pituicytes. They stores and releases two major
hormones ADH and Oxytocin.
 ADH is formed in supraoptic nuclei of hypothalamus
and oxytocin in paraventricular nuclei of
hypothalamus.
 ADH (antidiuretic hormone AKA vasopressin) as the
name indicates it decreases the production of urine
and retains it water in body. Dehydration or low B.P
stimulates synthesis of ADH.
 ADH helps in 3 ways-
1. It acts on sweat (sudoriferous) gland and
decreases the secretion of sweat.

19. 2. It causes reabsorption of water in kidneys.
3. It makes vasoconstriction and therefore
increases blood pressure. Therefore known as
vasopressin.
pain, stress, trauma, injury, anxitey and drugs
like morphine, nicotine, Ach stimulates ADH
secretion.
 Oxytocin- it is released during pregnancy. As the
concentration of progesterone decreases at the
end of pregnancy, production and release of
oxytocin is increased. It act upon the smooth
wall of uterus causing contraction. It also
stimulate smooth muscle of mammary gland to
contract and eject milk. 19

20. 20
TSH: thyroid-stimulating hormone
ACTH: adrenocorticotropic hormone
FSH: follicle-stimulating hormone
LH: luteinizing hormone
GH: growth hormone
PRL: prolactin
MSH: melanocyte-stimulating hormone
ADH: antidiuretic hormone
Oxytocin
TRH (thyroid releasing hormone)
turns on TSH
CRH (corticotropin releasing hormone)
turns on ACTH
GnRH (gonadotropin releasing hormone)
turns on FSH and LH
PRF (prolactin releasing hormone)
turns on PRL
GHRH (growth hormone releasing hm)
turns on GH
TSH stimulates the thyroid to produce
thyroid hormone
ACTH stimulates the adrenal cortex to
produce corticosteroids: aldosterone and
cortisol
FSH stimulates follicle growth and ovarian
estrogen production; stimulates sperm
production and androgen-binding protein
LH has a role in ovulation and the growth
of the corpus luteum; stimulates androgen
secretion by interstitial cells in testes
GH (aka somatrotropic hormone)
stimulates growth of skeletal epiphyseal
plates and body to synthesize protein
PRL stimulates mammary glands in breast
to make milk
MSH stimulates melanocytes; may
increase mental alertness
ADH (antidiuretic hormone or vasopressin)
stimulates the kidneys to reclaim more
water from the urine, raises blood pressure
Oxytocin prompts contraction of smooth
muscle in reproductive tracts, in females
initiating labor and ejection of milk from
Can we put it all together?
Blue is from hypothalamus
Black is from pituitary

21. 21
Pituitary__________
(hypophysis)
Hypothalamus___________
Now try and remember the anatomy

22. 22
The Thyroid Gland
 Anterior neck on trachea
below to larynx, in front of
2nd ,3rd, 4th tracheal ring.
 Two lateral lobes and an
isthmus(middle lobe).
 Gland is made up of
follicles and is lined by
cuboidal epithelium which
secretes colloid in lumen.
 This colloid contains
protein thyroglobulin
(iodine containing
glycoprotein).
 Parafollicular “C” cells:
produce calcitonin

23.  Under the influence of TSH follicular cells
Produces two hormones-
 Thyroid hormone: tyrosine based with 3 or 4
iodine molecules
 T4 (thyroxine/tetraiodothyronine) and T3
(triiodothyronine)
 Calcitonin involved with calcium and
phosphorus metabolism.
 50mg of iodine is required every year to
produce normal quantity of thyroid hormone.
 Iodine is absorbed from GIT, then it is either
excreted into urine or taken up by thyroid
gland and stored in form of thyroglobulin.
 80% of body iodine is located in thyroid gland.
23

24. Functions of thyroid hormones
 Increase in basal metabolic rate- 240 gm of
glucose release 1000 calories of energy but 1 mg of
thyroid hormone releases 1000 calories of energy.
 Effect on growth- promotes physical growth,
development of skeleton, sexual growth, mental growth,
development of brain in fetal life.
 Effect on protein, fat, carbohydrate
metabolism- helps in gluconeogenesis, glycolysis,
mobilisation of fat from adipose tissue
 Effect on heart- increases heart rate, force of
cntraction, activity of S.A node
 Other effects- increases muscle strength but on
excess secretion causes muscle weakness due to
excess protein catabolism. Excessive level causes
impotency.
24

25. 25
Some Effects of Thyroid Hormone
(Thyroxine)
 Increases the basal metabolic rate
 The rate at which the body uses oxygen to transform
nutrients (carbohydrates, fats and proteins) into
energy
 Affects many target cells throughout the body;
some effects are
 Protein synthesis
 Bone growth
 Neuronal maturation
 Cell differentiation

26. 26
Adrenal (suprarenal) glands
(“suprarenal” means on top of the kidney)
 Each is really two endocrine glands
 Adrenal cortex (outer)
 Adrenal medulla (inner)
 Unrelated chemicals but all help with extreme situations

27. 27
Adrenal Gland
 Adrenal cortex-
 Made up of 3 zones- zona glomerulosa, zona
fassiculata, zona reticularis
 Secretes lipid-based steroid hormones, called
“corticosteroids” – “cortico” as in “cortex”
 MINERALOCORTICOIDS
– Aldosterone is the main one
 GLUCOCORTICOIDS
– Cortisol (hydrocortisone) is the main one
 Adrenal medulla-
 It is made up of chromaffin cells. It secretes
epinephrine and norepinephrine

28. 28
Aldosterone, the main mineralocorticoid
 Secreted by adrenal cortex in response to
a decline in either blood volume or blood
pressure (e.g. severe hemorrhage)
 Is terminal hormone in renin-angiotensin
mechanism
 Prompts distal and collecting tubules in
kidney to reabsorb more sodium
 Water passively follows
 Blood volume thus increases

29. 29
Cortisol, the most important glucocorticoid
(Glucocorticoid receptors are found in the cells of most vertebrate tissues)
 It is essential for life
 Helps the body deal with stressful situations within
minutes
 Physical: trauma, surgery, exercise
 Psychological: anxiety, depression, crowding
 Physiological: fasting, hypoglycemia, fever, infection
 Regulates or supports a variety of important
cardiovascular, metabolic, immunologic, and
homeostatic functions including water balance
People with adrenal insufficiency: these stresses can cause hypotension, shock
and death: must give glucocorticoids, eg for surgery or if have infection, etc.

30. 30
Cortisol, continued
 Keeps blood glucose levels high enough to support
brain’s activity
 Forces other body cells to switch to fats and amino acids
as energy sources
 Catabolic: break down protein
 Redirects circulating lymphocytes to lymphoid and
peripheral tissues where pathogens usually are
 In large quantities, depresses immune and
inflammatory response
 Used therapeutically
 Responsible for some of its side effects

31. 31
Hormonal stimulation of glucocorticoids
HPA axis (hypothalamic/pituitary/adrenal axis)
 With stress, hypothalamus sends CRH to
anterior pituitary (adenohypophysis)
 Pituitary secretes ACTH
 ACTH goes to adrenal cortex where stimulates
glucocorticoid secretion
 Sympathetic nervous system can also stimulate it
 Adrenal cortex also secretes DHEA
(dehydroepiandrosterone)
 Converted in peripheral tissues to testosterone and
estrogen (also steroid hormones)
 Unclear function in relation to stress

32. 32
 Steroid-secreting cells
have abundant smooth
ER
 As opposed to rough ER
in protein-secreting cells
 Steroids directly diffuse
across plasma
membrane
 Not exocytosis
 Abundant lipid droplets
 Raw material from which
steroids made
In general:

33. 33
Adrenal medulla
 Part of autonomic
nervous system
 Spherical chromaffin
cells are modified
postganglionic
sympathetic neurons
 Secrete epinephrine
and norepinephrine
 Amine hormones
 Fight, flight, fright
 Vesicles store the
hormones

34. 34
The Pancreas
Exocrine and endocrine cells
 Acinar cells (forming most of the pancreas)
 Exocrine function
 Secrete digestive enzymes
 Islet cells (of Langerhans)
 Endocrine function

35. 35
Pancreatic islet
endocrine cells
Alpha cells: secrete glucagon
raises blood sugar
mostly in periphery
Beta cells: secrete insulin
lowers blood sugar
central part (are more abundant)
Also rare Delta cells:secrete
somatostatin(GHIH)
inhibits glucagon

36. Diabetes Mellitus
 Mostly due to decreased secretion of insulin from
beta cells of islet of langerhans of pancreas
 It may due to obesity which causes decrease in
number of insulin receptors target cells in body.
 It can be characterised by- hyperglycemia,
glucosuria, polyuria, polydipsia, polyphagia etc.
Type 1 diabetes mellitus or IDDM-
Progressive loss of beta cells and in severe case
its fully absent. In this insulin injections are given
to prevent death. Aka juvenile diabetes because
it may occur at the age of 20 and persist life long.
36

37. Type 2 Diabetes Mellitus or NIDDM
 It is commonest form and genetic factors play
major role in this condition.
 Generally observed in children above the age of
4 those are overweight.
 In this insulin level in blood is not low bur
condition is due to fact that insulin receptors
becomes less sensitive and even reduce in no.
 Beta cells of langerhans are active but problem
is with peripheral action of insulin. Therfore
known as NIDDM. Increased blood glucose level
can be controlled through diet, exercise, weight
loss etc.
37

38. 38
The Gonads (testes and ovaries)
main source of the steroid sex hormones
 Testes
 Interstitial cells secrete androgens
 Primary androgen is testosterone
 Maintains secondary sex characteristics
 Helps promote sperm formation
 Ovaries
 Androgens secreted by thecal folliculi
 Directly converted to estrogens by follicular granulosa cells
 Granulosa cells also produce progesterone
 Corpus luteum also secretes estrogen and progesterone

39. 39
Endocrine cells in various organs
 The heart: atrial natriuretic peptide (ANP)
 Stimulates kidney to secrete more salt
 Thereby decreases excess blood volume, high
BP and high blood sodium concentration
 GI tract & derivatives: Diffuse neuroendocrine
system (DNES)

40. 40
Endocrine cells in various organs continued
 The heart: atrial natriuretic peptide (ANP)
 Stimulates kidney to secrete more salt
 Thereby decreases excess blood volume, high BP and high blood
sodium concentration
 GI tract & derivatives: Diffuse neuroendocrine system (DNES)
 The placenta secretes steroid and protein hormones
 Estrogens, progesterone
 CRH
 HCG
 The kidneys
 Juxtaglomerular cells secrete renin
 Renin indirectly signals adrenal cortex to secrete aldosterone
 Erythropoietin: signals bone marrow to increase RBC production
 The skin
 Modified cholesterol with uv exposure becomes Vitamin D precursor
 Vitamin D necessary for calcium metabolism: signals intestine to absorb
CA++