introduction and pituitary gland Secretion, Function and Regulation

1. ENDOCRINE SYSTEM
SECRETIONS, REGULATION
AND FUNCTIONS
1
SELINA SRAVANTHI
SAROJINI NAIDU VANITA PHARMACY MAHA VIDYALAYA,
TARNAKA, HYDERABAD, TELANAGANA

2. NERVOUS AND ENDOCRINE SYSTEM
• The nervous and endocrine
systems act together to
coordinate functions of all body
systems.
• At synapses, nerve impulses
trigger the release of mediator
(messenger) molecules called
neurotransmitters
• The endocrine system also
controls body activities by
releasing mediators, called
hormones.
• A hormone is a mediator - that
is released in one part of the body
and regulates the activity of cells
in other parts of the body. 2

3. CHARACTERISTIC NERVOUS SYSTEM ENDOCRINE SYSTEM
Mediator molecules Neurotransmitters
released locally in
response to nerve
impulses
Hormones delivered to
tissues throughout the
body by the blood
Site of mediator action Close to site of release, at
a synapse; binds to
receptors inpostsynaptic
membrane
Far from site of release
(usually); binds to
receptors on or in target
cells
Types of target cells Muscle (smooth, cardiac,
and skeletal) cells, gland
cells, other neurons
Cells throughout the body.
Time to onset of action Typically within
milliseconds (thousandths
of a second).
Seconds to hours or days.
Duration of action Generally briefer
(milliseconds).
Generally longer (seconds
to days).
3

4. EXOCRINE AND ENDOCRINE GLANDS
• Body contains two kinds of glands:
• Exocrine glands-
– secrete their products into ducts that carry the secretions into body cavities,
into the lumen of an organ, or to the outer surface of the body.
– Ex: Sudoriferous (Sweat), Sebaceous (Oil), Mucous, and Digestive Glands.
• Endocrine glands –
– secrete their products (hormones) into the interstitial fluid surrounding the
secretory cells rather than into ducts.
– From the interstitial fluid, hormones diffuse into blood capillaries and blood
carries them to target cells throughout the body.
– Hormones are required in very small amounts, circulating levels typically
are low.
– Ex: Pituitary, Thyroid, Parathyroid, Adrenal, and Pineal Glands
• Several organs and tissues are not endocrine glands but contain cells that
secrete hormones. Ex: Hypothalamus, Thymus, Pancreas, Ovaries,
Testes, Kidneys, Stomach, Liver, Small Intestine, Skin, Heart, Adipose
Tissue, and Placenta.
• Taken together, all ENDOCRINE GLANDS and HORMONE-
SECRETING CELLS constitute the ENDOCRINE SYSTEM.
4

5. TERMINOLOGY
• CIRCULATING HORMONES
• secretory cells - interstitial fluid – blood
• LOCAL HORMONES
• -act on neighboring cells or same cell before entering blood stream
• PARACRINE- act on neighboring cell
• AUTOCRINE- act on same cell
5

6. HYPOTHALAMUS AND PITUITARY GLAND
• Master gland- secretes several hormones that control
other endocrine glands.
• Pituitary gland itself has a master—the
Hypothalamus.
• major link between the nervous and endocrine
systems.
• Cells in the hypothalamus synthesize at least nine
different hormones,
• Cells in the pituitary gland secretes seven different
hormones.
• Together, these hormones – regulate all aspects of
growth, development, metabolism, and homeostasis6

7. HYPOTHALAMUS AND PITUITARY GLAND
It is a pea shaped structure.
Lies in the hypophyseal fossa of the sphenoid bone
Attaches to the hypothalamus by a stalk- Infundibulum
Downgrowth of
nervous tissue of brain
Upgrowth of glandular
epithelium of pharynx
7

8. ANTERIOR PITUITARY/
ADENOHYPOPHYSIS
•Secretes hormones that regulate a wide range of bodily activities,
from growth to reproduction.
•Release of anterior pituitary hormones is stimulated by releasing
hormones and suppressed by inhibiting hormones from the
hypothalamus.
•Secretion of anterior pituitary hormones is regulated in two ways.
•First, neurosecretory cells in the hypothalamus secrete five
releasing hormones, which stimulate secretion of anterior pituitary
hormones, and two inhibiting hormones, which suppress secretion
of anterior pituitary hormones
•Second, negative feedback in the form of hormones released by
target glands decreases secretions of three types of anterior pituitary
cells- thyrotrophs, gonadotrophs, and corticotrophs
8

9. HORMONES OF ANTERIOR
PITUITARY GLAND
1. HUMAN GROWTH HORMONE (hGH)/
SOMATOTROPIN
2. THYROID STIMULATING HORMONE (TSH)/
THYROTROPIN
3. FOLLICLE STIMULATING HORMONE(FSH)
4. LUTEINIZING HORMONE (LH)
5. PROLACTIN (PRL)
6. ADRENOCORTICOTROPIC HORMONE (ACTH)
7. MELANOCYTE STIMULATING HORMONE
(MSH)
9

10. HORMONES OF HYPOTHALAMUS
RELEASING HORMONES
• Growth Hormone Releasing
Hormone (GHRH)
• Throtropin Releasing
Hormone (TRH)
• Gonadotropin Releasing
Hormone (GnRH)
• Prolactin Releasing Hormone
(PRH)
• Corticotropin Releasing
Hormone (CRH)
INHIBITORY HORMONES
• Growth Hormone Inhibitory
Hormone (GHIH)
• Prolactin Inhibitory
Hormone (PIH)/ Dopamine
• Dopamine
10

11. ANTERIOR PITUITARY/ ADENOHYPOPHYSIS
TYPES OF ANTERIOR PITUITARY CELLS
1. SOMATOTROPHS secrete human growth hormone (hGH) or
somatotropin. Human growth hormone in turn stimulates several tissues to secrete
insulin like growth factors, hormones that stimulate general body growth and
regulate aspects of metabolism.
2. THYROTROPHS secrete thyroid-stimulating hormone (TSH) or
thyrotropin controls the secretions and other activities of the thyroid gland.
3. GONADOTROPHS secrete two gonadotropins: follicle-stimulating hormone
(FSH) and luteinizing hormone (LH) FSH and LH both act on the gonads.
They stimulate secretion of estrogens and progesterone and the maturation of
oocytes in the ovaries, and they stimulate sperm production and secretion of
testosterone in the testes.
4. LACTOTROPHS secrete prolactin (PRL)- initiates milk production in the
mammary glands.
5. CORTICOTROPHS secrete adrenocorticotropic hormone (ACTH) or
corticotropin- Stimulates the adrenal cortex to secrete glucocorticoid such as
cortisol. Some corticotrophs, secrete melanocyte-stimulating hormone (MSH).11

12. HUMAN GROWTH HORMONE AND
INSULIN LIKE GROWTH FACTORS
• Somatotrophs are the most numerous cells- human growth hormone (hGH) is the
most plentiful anterior pituitary hormone.
• The main function of hGH is to promote synthesis and secretion of small protein
hormones called insulin like growth factors (IGFs) or somatomedins.
• In response to human growth hormone, cells in the liver, skeletal muscles,
cartilage, bones, and other tissues secrete IGFs, which may either enter the
bloodstream from the liver or act locally in other tissues as autocrines or
paracrines.
• FUNCTIONS OF IGFs
• During childhood and teenage- cause cells to grow and multiply- increases
growth rate of skeleton and skeletal muscles.
• In adults- help maintain muscle and bone mass, promote healing of injuries and
tissue repair.
• Enhance lipolysis- to produce ATP from fatty acids.
• Decreases Glucose uptake by body cells - spares glucose so that it is available to
neurons for ATP production.
• Stimulate liver cells to release glucose into the blood.
12

13. Secretion of hGH is stimulated by growth hormone–
releasing hormone (GHRH) and inhibited by growth
hormone–inhibiting hormone (GHIH)
Other factors that
promote hGH:
•Decreased fatty
acids,
•Increased AA
•Deep sleep
•Increased activity
of sympathetic NS-
stress, physical
exercise
•Other hormones
like glucagon,
estrogens, cortisol,
insulin
Other factors that
inhibit hGH:
•Increased fatty
acids,
•Decreased AA
•Not Deep sleep
•Obesity
•Emotional
deprivation
•Low level of
thyroid hormones
and hGH
•Growth hormone-
inhibitting
Hormone
(Somatostatin)
13

14. THYROID STIMULATING
HORMONE
•Thyroid-stimulating hormone (TSH) stimulates the
synthesis and secretion of the two thyroid hormones,
TRIIODOTHYRONINE (T3) and THYROXINE (T4),
both produced by the thyroid gland.
•Thyrotropin-releasing hormone (TRH) from the
hypothalamus controls TSH secretion.
• Release of TRH in turn depends on blood levels of T3
and T4; high levels of T3 and T4 inhibit secretion of TRH
via negative feedback.
•THERE IS NO THYROTROPIN INHIBITING
HORMONE. 14

15. FOLLICLE STIMULATING
HORMONE
•In females, the ovaries are the targets for follicle-
stimulating hormone (FSH).
• Each month FSH initiates the development of several
ovarian follicles.
•FSH also stimulates follicular cells to secrete estrogens
(female sex hormones).
•In males, FSH stimulates sperm production in the testes.
• Gonadotropin releasing hormone (GnRH) from the
hypothalamus stimulates FSH release.
•Release of GnRH and FSH is suppressed by estrogens in
females and by testosterone (the principal male sex
hormone) in males through negative feedback systems.
• THERE IS NO GONADOTROPIN-INHIBITING
HORMONE.
15

16. LUTEINIZING HORMONE
• In females, luteinizing hormone (LH) triggers ovulation, the
release of a secondary oocyte (future ovum) by an ovary.
• LH stimulates formation of the corpus luteum (structure formed
• after ovulation) in the ovary and the secretion of progesterone
another female sex hormone) by the corpus luteum.
• Together, FSH and LH also stimulate secretion of estrogens by
ovarian cells. Estrogens and progesterone prepare the uterus for
• implantation of a fertilized ovum and help prepare the mammary
glands for milk secretion.
• In males, LH stimulates cells in the testes to secrete
testosterone.
• Secretion of LH, like that of FSH, is controlled by gonadotropin-
releasing hormone (GnRH).
16

17. PROLACTIN
• Prolactin (PRL), together with other hormones, initiates and
maintains milk secretion by the mammary glands.
• By itself, prolactin has only a weak effect.
• Only after the mammary glands have been primed by estrogens,
progesterone, glucocorticoids, human growth hormone, thyroxine,
and insulin, which exert permissive effects, does PRL bring about
milk secretion.
• Ejection of milk from the mammary glands depends on the
hormone oxytocin, which is released from the posterior pituitary.
• Together, milk secretion and ejection constitute lactation.
• The hypothalamus secretes both inhibitory and excitatory
hormones that regulate prolactin secretion. In females,
prolactin-inhibiting hormone (PIH), which is dopamine, inhibits
the release of prolactin from the anterior pituitary most of the
time.
17

18. PROLACTIN
• Each month, just before menstruation begins, the secretion of PIH
diminishes and the blood level of prolactin rises, but not enough to
stimulate milk production. Breast tenderness just before
menstruation may be caused by elevated prolactin. As the
menstrual cycle begins anew, PIH is again secreted and the
prolactin level drops.
• During pregnancy, the prolactin level rises, stimulated by
prolactin- releasing hormone (PRH) from the hypothalamus.
The sucking action of a nursing infant causes a reduction in
hypothalamic secretion of PIH.
• The function of prolactin is not known in males, but its
hypersecretion causes erectile dysfunction (impotence, the
inability to have an erection of the penis).
• In females, hypersecretion of prolactin causes galactorrhea
(inappropriate lactation) and amenorrhea (absence of menstrual
cycles). 18

19. ADRENOCORTICOTROPIC HORMONE
• Corticotrophs secrete mainly adrenocorticotropic hormone
(ACTH).
• ACTH controls the production and secretion of cortisol
and other glucocorticoids by the cortex (outer portion)
of the adrenal glands.
• Corticotropin-releasing hormone (CRH) from the
hypothalamus stimulates secretion of ACTH by
corticotrophs.
• Stress-related stimuli, such as low blood glucose or
physical trauma, and interleukin-1, a substance produced
by macrophages, also stimulate release of ACTH.
• Glucocorticoids inhibit CRH and ACTH release via
negative feedback.
19

20. MELANOCYTE STIMULATING
HORMONE
• Melanocyte-stimulating hormone (MSH) increases
skin pigmentation in amphibians by stimulating the
dispersion of melanin granules in melanocytes.
• Its exact role in humans is unknown, but the
presence of MSH receptors in the brain suggests it
may influence brain activity.
• There is little circulating MSH in humans.
However, continued administration of MSH for
several days does produce a darkening of the skin.
• Excessive levels of corticotropin-releasing
hormone (CRH) can stimulate MSH release;
dopamine inhibits MSH release.
20

21. POSTERIOR PITUITARY/
NEUROHYPOPHYSIS
•Does not synthesize hormones.
•It stores and release two hormones-
oxytocin and vasopressin
•Paraventricular nucleus synthesizes-
oxytocin
•Supraoptic nucleus produces
antidiuretic hormone (ADH) or
vasopressin
•After production- oxytocin and
antidiuretic hormone are packaged into
secretory vesicles, which move by fast
axonal transport to the axon terminals
in the posterior pituitary, where they are
stored until nerve impulses trigger
exocytosis and release of the hormone. 21

22. OXYTOCIN
• During and after delivery of a baby, oxytocin affects
two target tissues: the mother’s uterus and breasts.
• During delivery, oxytocin enhances contraction of
smooth muscle cells in the wall of the uterus
• after delivery, it stimulates milk ejection from the
mammary glands in response to the mechanical
stimulus provided by a suckling infant.
• The function of oxytocin in males and in
nonpregnant females is not clear.
• Experiments with animals have suggested that it has
actions within the brain that foster parental
caretaking behavior toward young offspring.
• It may also be responsible, in part, for the feelings of
sexual pleasure during and after intercourse.
22

23. ANTIDIURETIC HORMONE
• Antidiuretic hormone is a substance that decreases
urine production.
• ADH causes the kidneys to return more water to the
blood, thus decreasing urine volume.
• In the absence of ADH, urine output increases more
than tenfold, from the normal 1 to 2 liters to about 20
liters a day.
• Drinking alcohol often causes frequent and copious
urination because alcohol inhibits secretion of ADH.
• ADH also decreases the water lost through
sweating and causes constriction of arterioles,
which increases blood pressure.
• This hormone’s other name, vasopressin, reflects this
effect on blood pressure.
23

24. ANTIDIURETIC HORMONE
24

25. CELL HORMO
NE
FUNCTIONS REGULATIONSOMATOTROPHS
HumanGrowthHormone(hGH)/Somatotropin •Promote synthesis of IGFs
•Increase growth rate of
skeleton and
muscles(children and
teenagers)
•Maintain muscle and bone
mass promote healing, tissue
repair (adults)
•Enhance lipolysis- to
produce ATP from fatty acids.
•Decreases Glucose uptake by
body cells - spares glucose so
that it is available to neurons
for ATP production.
•Stimulate liver cells to
release glucose into the
blood.
•Growth Hormone- Releasing Hormone
(GHRH)- stimulates hGH –
•Other stimulators -Decreased fatty acids,
Increased AA, Deep sleep, Increased
activity of sympathetic NS-stress, physical
exercise, Other hormones like glucagon,
estrogens, cortisol, insulin
•Growth Hormone- Inhibiting Hormone
(GHIH) – inhbits hGH
•Other inhibitors- Increased fatty acids,
Decreased AA, No Deep sleep, Obesity,
Emotional deprivation, Low level of thyroid
hormones and hGH (Somatostatin)
•GHRH and GHIH- controlled by glucose
blood levels
HYROTROPHS
Thyroid
Stimulating
ormone(TSH)
stimulates synthesis and
secretion of
TRIIODOTHYRONINE (T3) and
THYROXINE (T4)
Thyrotropin-releasing hormone (TRH)
controls TSH secretion.
Release of TRH- depends on blood levels of
T3 and T4 (High levels - negative feedback
mechanism)
25

26. CELL HORMO
NE
FUNCTIONS REGULATIONGONADOTROPHS
Folliclestimulating
Hormone(FSH)
•In females, Initiates the development of
several ovarian follicles
•Stimulates follicular cells to secrete estrogens
•In males- stimulates sperm production in the
testes.
•Gonadotropin releasing
hormone (GnRH) regulates
FSH
•GnRH and FSH is
suppressed by estrogens &
testosterone (negative
feedback systems)
LeutinizingHormone(LH)
•Triggers ovulation
•Stimulates formation of the corpus luteum &
secretion of progesterone by the corpus
luteum.
•FSH and LH also stimulate secretion of
estrogens by ovarian cells.
•Estrogens and progesterone prepare the
uterus for implantation & help prepare the
mammary glands for milk secretion.
In males, -stimulates cells in the testes to
secrete testosterone.
Gonadotropin releasing
hormone (GnRH) regulates
LH
26

27. CELL HORM
ONE
FUNCTION REGULATIONLACTO-TROPHS
Prolactin(PRL) •Together with other
hormones initiates and
maintains milk secretion.
•Breast tenderness before
menstruation
•In females, prolactin-inhibiting hormone (PIH)-
dopamine, inhibits the release of prolactin as
menstrual cycle begins.
•During pregnancy, the prolactin level rises,
stimulated by prolactin- releasing hormone
(PRH)
•The sucking action of a nursing infant causes a
reduction in hypothalamic secretion of PIH.
CORTICOTROPHS
Adrenocortico-
trophicHormone
(ACTH)
•secrete adrenocorticotropic
hormone (ACTH).
•ACTH - production and
secretion of cortisol and
glucocorticoids by the cortex
of the adrenal glands.
•Corticotropin-releasing hormone (CRH)
stimulates secretion of ACTH
•Stress-related stimuli- Low blood glucose or
physical trauma, and interleukin-1, produced by
macrophages, also stimulate release of ACTH.
•Glucocorticoids inhibit CRH and ACTH
(negative feedback).
Melanocyte
Stimulating
Hormone(MSH)
•Role in humans is unknown
•Presence of MSH receptors
in the brain may influence
brain activity.
•Administration of MSH for
several days -darkening of
the skin.
•Excessive levels of Corticotropin Releasing
Hormone (CRH) can stimulate MSH release
•Dopamine inhibits MSH release.
27

28. CELL HORMONE FUNCTIONS REGULATIONNeronalbodiesin
paraventricularnucleus
OXYTOCIN
•During delivery, oxytocin enhances
contraction of smooth muscle cells
in the wall of the uterus
•After delivery, it stimulates milk
ejection from the mammary glands
in response to the mechanical
stimulus provided by a suckling
infant.
•Regulated by Uterine
Distension and Stimulation of
Nipples
Neuronalbodiesin
supraopticnucleus
ANTIDIURETICHORMONE
(ADH)/VASOPRESSIN
•decreases urine production by
causing the kidneys to return more
water to the blood, thus decreasing
urine volume.
•decreases the water lost through
sweating
•causes constriction of arterioles,
which increases blood pressure.
•Secreted by elevated levels of
Blood Osmotic Pressure and
less Blood Volume,
dehydration, pain or stress
•Inhibittors –low blood
osmaotic pressure, high blood
volume and alcohol
28