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CHAPTER
16
Part A
HUMAN ANATOMY AND PHYSIOLOGY II
1
CASE STUDY


Chief Complaint: 8 year old girl with excessive thirst,
frequent urination, and weight loss
History: History: Cindy Mallon, an 8-year-old girl in
previously good health, has noticed that, in the past
month, she is increasingly thirsty. She gets up several
times a night to urinate, and finds herself gulping down
glassfulls of water. At the dinner table, she seems to be
eating twice as much as she used to, yet she has lost 5
pounds in the past month. In the past three days, she
has become nauseated, vomiting on three occasions,
prompting a visit to her pediatrician.
2
CASE STUDY
At the doctor's office, blood and urine samples
are taken. The following lab results are noted:
 blood glucose level = 545 mg/dl (normal 50170 mg/dl)
 blood pH level = 7.23 (normally 7.35-7.45)
 urine = tested positive for glucose and ketone
bodies (normally urine is free of glucose and
ketone bodies)

3
THE DIABETES EPIDEMIC
4
ENDOCRINE SYSTEM: OVERVIEW
Acts with nervous system to coordinate and
integrate activity of body cells
 Influences metabolic activities via hormones
transported in blood
 Response slower but longer lasting than
nervous system
 Endocrinology

 Study
of hormones and endocrine organs
Slide 1
ENDOCRINE SYSTEM: OVERVIEW

Controls and integrates
 Reproduction
 Growth
and development
 Maintenance of electrolyte, water, and nutrient
balance of blood
 Regulation of cellular metabolism and energy
balance
 Mobilization of body defenses
Slide 2
ENDOCRINE SYSTEM: OVERVIEW

Exocrine glands
 Nonhormonal
substances (sweat, saliva)
 Have ducts to carry secretion to membrane surface

Endocrine glands
 Produce
hormones
 Lack ducts
Slide 3
ENDOCRINE SYSTEM: OVERVIEW
Endocrine glands: pituitary, thyroid,
parathyroid, adrenal, and pineal glands
 Hypothalamus is Neuroendocrine organ
 Some have exocrine and endocrine functions

 Pancreas,

gonads, placenta
Other tissues and organs that produce
hormones
 Adipose
cells, thymus, and cells in walls of small
intestine, stomach, kidneys, and heart
Slide 4
Figure 16.1 Location of selected endocrine organs of the body.
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
(on dorsal aspect
of thyroid gland)
Thymus
Adrenal glands
Pancreas
Gonads
• Ovary (female)
• Testis (male)
Slide 5
CHEMICAL MESSENGERS
Hormones: long-distance chemical signals;
travel in blood or lymph
 Autocrines: chemicals that exert effects on
same cells that secrete them
 Paracrines: locally acting chemicals that affect
cells other than those that secrete them
 Autocrines and paracrines are local chemical
messengers; not considered part of endocrine
system

Slide 6
CHEMISTRY OF HORMONES

Two main classes
 Amino
acid-based hormones
 Amino
acid derivatives, peptides, and proteins
 Steroids
 Synthesized
from cholesterol
 Gonadal and adrenocortical hormones
Slide 7
MECHANISMS OF HORMONE ACTION
Though hormones circulate systemically only
cells with receptors for that hormone affected
 Target cells

 Tissues

with receptors for specific hormone
Hormones alter target cell activity
Slide 8
MECHANISMS OF HORMONE ACTION

Hormone action on target cells may be to
 Alter
plasma membrane permeability and/or
membrane potential by opening or closing ion
channels
 Stimulate synthesis of enzymes or other proteins
 Activate or deactivate enzymes
 Induce secretory activity
 Stimulate mitosis
Slide 9
MECHANISMS OF HORMONE ACTION

Hormones act at receptors in one of two ways,
depending on their chemical nature and
receptor location
1.
Water-soluble hormones (all amino acid–based
hormones except thyroid hormone)



Act on plasma membrane receptors
Act via G protein second messengers
Cannot enter cell
Slide 10
MECHANISMS OF HORMONE ACTION
2. Lipid-soluble hormones (steroid and thyroid
hormones)


Act on intracellular receptors that directly activate
genes
Can enter cell
Slide 11
PLASMA MEMBRANE RECEPTORS AND SECONDMESSENGER SYSTEMS

cAMP signaling mechanism:
1.
2.
3.
4.
5.
Hormone (first messenger) binds to receptor
Receptor activates G protein
G protein activates adenylate cyclase
Adenylate cyclase converts ATP to cAMP (second
messenger)
cAMP activates protein kinases that
phosphorylate proteins
Slide 12
PLASMA MEMBRANE RECEPTORS AND SECONDMESSENGER SYSTEMS

cAMP signaling mechanism
 Activated
kinases phosphorylate various proteins,
activating some and inactivating others
 cAMP is rapidly degraded by enzyme
phosphodiesterase
 Intracellular enzymatic cascades have huge
amplification effect
Slide 13
FIGURE 16.2 CYCLIC AMP SECOND-MESSENGER MECHANISM OF WATER-SOLUBLE HORMONES.
Recall from Chapter 3 that
G protein signaling mechanisms
are like a molecular relay race.
Hormone Receptor G protein Enzyme
2nd
(1st messenger)
messenger
1 Hormone (1st messenger)
binds receptor.
Extracellular fluid
Adenylate cyclase
G protein (Gs)
Receptor
5 cAMP activates
protein kinases.
cAMP
GTP
GTP
ATP
GDP
Inactive
protein
kinase
GTP
Active
protein
kinase
Triggers responses of
target cell (activates
enzymes, stimulates
cellular secretion,
opens ion channel, etc.)
Cytoplasm
2 Receptor
activates G
protein (Gs).
3 G protein
activates
adenylate
cyclase.
4 Adenylate
cyclase converts
ATP to cAMP (2nd
messenger).
Slide 14
FIGURE 16.2 CYCLIC AMP SECOND-MESSENGER MECHANISM OF WATER-SOLUBLE HORMONES.
Recall from Chapter 3 that
G protein signaling mechanisms
are like a molecular relay race.
1 Hormone (1st messenger)
binds receptor.
Hormone Receptor G protein Enzyme
2nd
(1st messenger)
messenger
Extracellular fluid
Receptor
Cytoplasm
Slide 15
FIGURE 16.2 CYCLIC AMP SECOND-MESSENGER MECHANISM OF WATER-SOLUBLE HORMONES.
Recall from Chapter 3 that
G protein signaling mechanisms
are like a molecular relay race.
Hormone Receptor G protein Enzyme
2nd
(1st messenger)
messenger
1 Hormone (1st messenger)
binds receptor.
Extracellular fluid
G protein (Gs)
Receptor
GTP
GDP
GTP
Cytoplasm
2 Receptor
activates G
protein (Gs).
Slide 16
FIGURE 16.2 CYCLIC AMP SECOND-MESSENGER MECHANISM OF WATER-SOLUBLE HORMONES.
Recall from Chapter 3 that
G protein signaling mechanisms
are like a molecular relay race.
Hormone Receptor G protein Enzyme
2nd
(1st messenger)
messenger
1 Hormone (1st messenger)
binds receptor.
Adenylate cyclase
Extracellular fluid
G protein (Gs)
GTP
Receptor
GTP
GDP
GTP
Cytoplasm
2 Receptor
activates G
protein (Gs).
3 G protein
activates
adenylate
cyclase.
Slide 17
FIGURE 16.2 CYCLIC AMP SECOND-MESSENGER MECHANISM OF WATER-SOLUBLE HORMONES.
Recall from Chapter 3 that
G protein signaling mechanisms
are like a molecular relay race.
Hormone Receptor G protein Enzyme
2nd
(1st messenger)
messenger
1 Hormone (1st messenger)
binds receptor.
Extracellular fluid
Adenylate cyclase
G protein (Gs)
cAMP
GTP
Receptor
GTP
ATP
GDP
GTP
Cytoplasm
2 Receptor
activates G
protein (Gs).
3 G protein
activates
adenylate
cyclase.
4 Adenylate
cyclase converts
ATP to cAMP (2nd
messenger).
Slide 18
FIGURE 16.2 CYCLIC AMP SECOND-MESSENGER MECHANISM OF WATER-SOLUBLE HORMONES.
Recall from Chapter 3 that
G protein signaling mechanisms
are like a molecular relay race.
Hormone Receptor G protein Enzyme
2nd
(1st messenger)
messenger
1 Hormone (1st messenger)
binds receptor.
Extracellular fluid
Adenylate cyclase
G protein (Gs)
Receptor
5 cAMP activates
protein kinases.
cAMP
GTP
GTP
ATP
GDP
Inactive
protein
kinase
GTP
Active
protein
kinase
Triggers responses of
target cell (activates
enzymes, stimulates
cellular secretion,
opens ion channel, etc.)
Cytoplasm
2 Receptor
activates G
protein (Gs).
3 G protein
activates
adenylate
cyclase.
4 Adenylate
cyclase converts
ATP to cAMP (2nd
messenger).
Slide 19
PLASMA MEMBRANE RECEPTORS AND SECONDMESSENGER SYSTEMS

PIP2-calcium signaling mechanism
 Involves
G protein and membrane-bound effector –
phospholipase C
 Phospholipase C splits PIP2 into two second
messengers – diacylglycerol (DAG) and inositol
trisphosphate (IP3)
 DAG
activates protein kinase; IP3 causes Ca2+ release
 Calcium ions act as second messenger
PLASMA MEMBRANE RECEPTORS AND SECONDMESSENGER SYSTEMS
 Ca2+
alters enzyme activity and channels, or binds
to regulatory protein calmodulin
 Calcium-bound calmodulin activates enzymes that
amplify cellular response
OTHER SIGNALING MECHANISMS
Cyclic guanosine monophosphate (cGMP) is
second messenger for some hormones
 Some work without second messengers

 E.g.,
insulin receptor is tyrosine kinase enzyme that
autophosphorylates upon insulin binding 
docking for relay proteins that trigger cell responses
INTRACELLULAR RECEPTORS AND DIRECT GENE
ACTIVATION

Steroid hormones and thyroid hormone
1.
2.
3.
4.
5.
Diffuse into target cells and bind with intracellular
receptors
Receptor-hormone complex enters nucleus; binds
to specific region of DNA
Prompts DNA transcription to produce mRNA
mRNA directs protein synthesis
Promote metabolic activities, or promote
synthesis of structural proteins or proteins for
export from cell
FIGURE 16.3 DIRECT GENE ACTIVATION MECHANISM OF LIPID-SOLUBLE HORMONES.
Extracellular
fluid
Steroid
hormone
Plasma
membrane
Cytoplasm
Receptor
protein
Nucleus
1 The steroid hormone
diffuses through the plasma
membrane and binds an
intracellular receptor.
Receptorhormone
complex 2 The receptorhormone complex enters the
nucleus.
Receptor
Binding region
DNA
mRNA
3 The receptor- hormone
complex binds a specific DNA
region.
4 Binding initiates
transcription of the gene to
mRNA.
5 The mRNA directs protein
synthesis.
New protein
FIGURE 16.3 DIRECT GENE ACTIVATION MECHANISM OF LIPID-SOLUBLE HORMONES.
Extracellular
fluid
Steroid
hormone
Plasma
membrane
Cytoplasm
Receptor
protein
Nucleus
Receptorhormone
complex
1 The steroid hormone
diffuses through the plasma
membrane and binds an
intracellular receptor.
FIGURE 16.3 DIRECT GENE ACTIVATION MECHANISM OF LIPID-SOLUBLE HORMONES.
Extracellular
fluid
Steroid
hormone
Cytoplasm
Receptor
protein
Nucleus
Plasma
membrane
1 The steroid hormone
diffuses through the plasma
membrane and binds an
intracellular receptor.
Receptorhormone
complex 2 The receptorhormone complex enters the
nucleus.
FIGURE 16.3 DIRECT GENE ACTIVATION MECHANISM OF LIPID-SOLUBLE HORMONES.
Extracellular
fluid
Steroid
hormone
Plasma
membrane
Cytoplasm
Receptor
protein
Nucleus
1 The steroid hormone
diffuses through the plasma
membrane and binds an
intracellular receptor.
Receptorhormone
complex 2 The receptorhormone complex enters the
nucleus.
Receptor
Binding region
DNA
3 The receptor- hormone
complex binds a specific DNA
region.
FIGURE 16.3 DIRECT GENE ACTIVATION MECHANISM OF LIPID-SOLUBLE HORMONES.
Extracellular
fluid
Steroid
hormone
Plasma
membrane
Cytoplasm
Receptor
protein
Nucleus
Receptorhormone
complex 2 The receptorhormone complex enters the
nucleus.
Receptor
Binding region
DNA
mRNA
1 The steroid hormone
diffuses through the plasma
membrane and binds an
intracellular receptor.
3 The receptor- hormone
complex binds a specific DNA
region.
4 Binding initiates
transcription of the gene to
mRNA.
FIGURE 16.3 DIRECT GENE ACTIVATION MECHANISM OF LIPID-SOLUBLE HORMONES.
Extracellular
fluid
Steroid
hormone
Plasma
membrane
Cytoplasm
Receptor
protein
Nucleus
1 The steroid hormone
diffuses through the plasma
membrane and binds an
intracellular receptor.
Receptorhormone
complex 2 The receptorhormone complex enters the
nucleus.
Receptor
Binding region
DNA
mRNA
3 The receptor- hormone
complex binds a specific DNA
region.
4 Binding initiates
transcription of the gene to
mRNA.
5 The mRNA directs protein
synthesis.
New protein
TARGET CELL SPECIFICITY

Target cells must have specific receptors to
which hormone binds, for example
 ACTH
receptors found only on certain cells of
adrenal cortex
 Thyroxin receptors are found on nearly all cells of
body
TARGET CELL ACTIVATION

Target cell activation depends on three factors
 Blood
levels of hormone
 Relative number of receptors on or in target cell
 Affinity of binding between receptor and hormone
TARGET CELL ACTIVATION

Hormones influence number of their receptors
 Up-regulation—target
cells form more receptors in
response to low hormone levels
 Down-regulation—target cells lose receptors in
response to high hormone levels
CONTROL OF HORMONE RELEASE

Blood levels of hormones
 Controlled
by negative feedback systems
 Vary only within narrow, desirable range

Endocrine gland stimulated to synthesize and
release hormones in response to
 Humoral
stimuli
 Neural stimuli
 Hormonal stimuli
HUMORAL STIMULI
Changing blood levels of ions and nutrients
directly stimulate secretion of hormones
 Example: Ca2+ in blood

 Declining
blood Ca2+ concentration stimulates
parathyroid glands to secrete PTH (parathyroid
hormone)
 PTH causes Ca2+ concentrations to rise and
stimulus is removed
Figure 16.4a Three types of endocrine gland stimuli.
Humoral Stimulus
Hormone release caused by altered
levels of certain critical ions or
nutrients.
Capillary (low Ca2+
in blood)
Thyroid gland
(posterior view)
Parathyroid
glands
Parathyroid
glands
PTH
Stimulus: Low concentration of Ca2+ in
capillary blood.
Response: Parathyroid glands secrete
parathyroid hormone (PTH), which
increases blood Ca2+.
Figure 16.4a Three types of endocrine gland stimuli.
Humoral Stimulus
Hormone release caused by altered
levels of certain critical ions or
nutrients.
Capillary (low Ca2+
in blood)
Parathyroid
glands
Thyroid gland
(posterior view)
Parathyroid
glands
Figure 16.4a Three types of endocrine gland stimuli.
Humoral Stimulus
Hormone release caused by altered
levels of certain critical ions or
nutrients.
Capillary (low Ca2+
in blood)
Thyroid gland
(posterior view)
Parathyroid
glands
Parathyroid
glands
PTH
Stimulus: Low concentration of Ca2+ in
capillary blood.
Response: Parathyroid glands secrete
parathyroid hormone (PTH), which
increases blood Ca2+.
HORMONAL STIMULI

Hormones stimulate other endocrine organs to
release their hormones
 Hypothalamic
hormones stimulate release of most
anterior pituitary hormones
 Anterior pituitary hormones stimulate targets to
secrete still more hormones
 Hypothalamic-pituitary-target endocrine organ
feedback loop: hormones from final target organs
inhibit release of anterior pituitary hormones
Figure 16.4c Three types of endocrine gland stimuli.
Hormonal Stimulus
Hormone release caused by another
hormone (a tropic hormone).
Hypothalamus
Anterior
pituitary
gland
Thyroid
gland
Adrenal Gonad
cortex (Testis)
Stimulus: Hormones from hypothalamus.
Response: Anterior pituitary gland secretes
hormones that stimulate other endocrine
glands to secrete hormones.
Figure 16.4c Three types of endocrine gland stimuli.
Hormonal Stimulus
Hormone release caused by another
hormone (a tropic hormone).
Hypothalamus
Anterior
pituitary
gland
Thyroid
gland
Adrenal Gonad
cortex (Testis)
Figure 16.4c Three types of endocrine gland stimuli.
Hormonal Stimulus
Hormone release caused by another
hormone (a tropic hormone).
Hypothalamus
Anterior
pituitary
gland
Thyroid
gland
Adrenal Gonad
cortex (Testis)
Figure 16.4c Three types of endocrine gland stimuli.
Hormonal Stimulus
Hormone release caused by another
hormone (a tropic hormone).
Hypothalamus
Anterior
pituitary
gland
Thyroid
gland
Adrenal Gonad
cortex (Testis)
Stimulus: Hormones from hypothalamus.
Response: Anterior pituitary gland secretes
hormones that stimulate other endocrine
glands to secrete hormones.
NEURAL STIMULI

Nerve fibers stimulate hormone release
 Sympathetic
nervous system fibers stimulate
adrenal medulla to secrete catecholamines
Figure 16.4b Three types of endocrine gland stimuli.
Neural Stimulus
Hormone release caused
by neural input.
CNS (spinal cord)
Preganglionic
sympathetic
fibers
Medulla of
adrenal gland
Capillary
Stimulus: Action potentials in preganglionic
sympathetic fibers to adrenal medulla.
Response: Adrenal medulla cells secrete
epinephrine and norepinephrine.
Figure 16.4b Three types of endocrine gland stimuli.
Neural Stimulus
Hormone release caused
by neural input.
CNS (spinal cord)
Preganglionic
sympathetic
fibers
Medulla of
adrenal gland
Capillary
Figure 16.4b Three types of endocrine gland stimuli.
Neural Stimulus
Hormone release caused
by neural input.
CNS (spinal cord)
Preganglionic
sympathetic
fibers
Medulla of
adrenal gland
Capillary
Stimulus: Action potentials in preganglionic
sympathetic fibers to adrenal medulla.
Response: Adrenal medulla cells secrete
epinephrine and norepinephrine.
NERVOUS SYSTEM MODULATION

Nervous system modifies stimulation of
endocrine glands and their negative feedback
mechanisms
 Example:
under severe stress, hypothalamus and
sympathetic nervous system activated


 body glucose levels rise
Nervous system can override normal endocrine
controls
HORMONES IN THE BLOOD

Hormones circulate in blood either free or
bound
 Steroids
and thyroid hormone are attached to
plasma proteins
 All others circulate without carriers

Concentration of circulating hormone reflects
 Rate
of release
 Speed of inactivation and removal from body
HORMONES IN THE BLOOD

Hormones removed from blood by
 Degrading
enzymes
 Kidneys
 Liver
 Half-life—time
required for hormone's blood level to
decrease by half

Varies from fraction of minute to a week
ONSET OF HORMONE ACTIVITY
Some responses ~ immediate
 Some, especially steroid, hours to days
 Some must be activated in target cells

DURATION OF HORMONE ACTIVITY

Limited
 Ranges
from 10 seconds to several hours
 Effects may disappear as blood levels drop
 Some persist at low blood levels
INTERACTION OF HORMONES AT TARGET CELLS

Multiple hormones may act on same target at
same time
 Permissiveness:
one hormone cannot exert its
effects without another hormone being present
 Synergism: more than one hormone produces same
effects on target cell  amplification
 Antagonism: one or more hormones oppose(s)
action of another hormone
THE PITUITARY GLAND AND HYPOTHALAMUS

Pituitary gland (hypophysis) has two major
lobes
 Posterior pituitary (lobe)
Neural
 Anterior
tissue
pituitary (lobe) (adenohypophysis)
Glandular
tissue
PITUITARY-HYPOTHALAMIC RELATIONSHIPS

Posterior pituitary (lobe)
 Downgrowth
of hypothalamic neural tissue
 Neural connection to hypothalamus (hypothalamichypophyseal tract)
 Nuclei of hypothalamus synthesize neurohormones
oxytocin and antidiuretic hormone (ADH)
 Neurohormones are transported to and stored in
posterior pituitary
Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).
Paraventricular nucleus
Hypothalamus
Posterior lobe
of pituitary
Optic
chiasma
Infundibulum
(connecting stalk)
Hypothalamichypophyseal
tract
Supraoptic
nucleus
Inferior
hypophyseal
artery
Axon terminals
1 Hypothalamic neurons
synthesize oxytocin or
antidiuretic hormone (ADH).
2 Oxytocin and ADH are
transported down the axons of
the hypothalamic- hypophyseal
tract to the posterior pituitary.
3 Oxytocin and ADH are
stored in axon terminals in
the posterior pituitary.
Posterior lobe
of pituitary
Oxytocin
ADH
4 When hypothalamic neurons
fire, action potentials arriving at
the axon terminals cause
oxytocin or ADH to be released
into the blood.
Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).
Paraventricular nucleus
Hypothalamus
Posterior lobe
of pituitary
Optic
chiasma
Infundibulum
(connecting stalk)
Hypothalamichypophyseal
tract
Axon terminals
Posterior lobe
of pituitary
Supraoptic
nucleus
Inferior
hypophyseal
artery
1 Hypothalamic neurons
synthesize oxytocin or
antidiuretic hormone (ADH).
Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).
Paraventricular nucleus
Hypothalamus
Posterior lobe
of pituitary
Optic
chiasma
Infundibulum
(connecting stalk)
Hypothalamichypophyseal
tract
Axon terminals
Posterior lobe
of pituitary
Supraoptic
nucleus
Inferior
hypophyseal
artery
1 Hypothalamic neurons
synthesize oxytocin or
antidiuretic hormone (ADH).
2 Oxytocin and ADH are
transported down the axons of
the hypothalamic- hypophyseal
tract to the posterior pituitary.
Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).
Paraventricular nucleus
Hypothalamus
Posterior lobe
of pituitary
Optic
chiasma
Infundibulum
(connecting stalk)
Hypothalamichypophyseal
tract
Axon terminals
Posterior lobe
of pituitary
Supraoptic
nucleus
Inferior
hypophyseal
artery
1 Hypothalamic neurons
synthesize oxytocin or
antidiuretic hormone (ADH).
2 Oxytocin and ADH are
transported down the axons of
the hypothalamic- hypophyseal
tract to the posterior pituitary.
3 Oxytocin and ADH are
stored in axon terminals in
the posterior pituitary.
Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).
Paraventricular nucleus
Hypothalamus
Posterior lobe
of pituitary
Optic
chiasma
Infundibulum
(connecting stalk)
Hypothalamichypophyseal
tract
Supraoptic
nucleus
Inferior
hypophyseal
artery
Axon terminals
1 Hypothalamic neurons
synthesize oxytocin or
antidiuretic hormone (ADH).
2 Oxytocin and ADH are
transported down the axons of
the hypothalamic- hypophyseal
tract to the posterior pituitary.
3 Oxytocin and ADH are
stored in axon terminals in
the posterior pituitary.
Posterior lobe
of pituitary
Oxytocin
ADH
4 When hypothalamic neurons
fire, action potentials arriving at
the axon terminals cause
oxytocin or ADH to be released
into the blood.
PITUITARY-HYPOTHALAMIC RELATIONSHIPS

Anterior Lobe:
 Originates
as out-pocketing of oral mucosa
 Vascular connection to hypothalamus
 Hypophyseal
portal system
Primary capillary plexus
 Hypophyseal portal veins
 Secondary capillary plexus
 Carries releasing and inhibiting hormones to anterior pituitary to
regulate hormone secretion

Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2).
Hypothalamus
Anterior lobe
of pituitary
Superior
hypophyseal
artery
2 Hypothalamic hormones
travel through portal veins to
the anterior pituitary where
they stimulate or inhibit
release of hormones made in
the anterior pituitary.
3 In response to releasing
hormones, the anterior
pituitary secretes hormones
into the secondary capillary
plexus. This in turn empties
into the general circulation.
GH, TSH, ACTH,
FSH, LH, PRL
Anterior lobe
of pituitary
Hypothalamic
neurons synthesize
GHRH, GHIH, TRH,
CRH, GnRH, PIH.
1 When appropriately stimulated,
hypothalamic neurons secrete
releasing or inhibiting hormones
into the primary capillary plexus.
Hypophyseal
portal system
• Primary capillary
plexus
• Hypophyseal
portal veins
• Secondary
capillary plexus
A portal
system is
two
capillary
plexuses
(beds)
connected
by veins.
Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2).
Hypothalamus
Anterior lobe
of pituitary
Superior
hypophyseal
artery
Hypothalamic
neurons synthesize
GHRH, GHIH, TRH,
CRH, GnRH, PIH.
1 When appropriately stimulated,
hypothalamic neurons secrete
releasing or inhibiting hormones
into the primary capillary plexus.
Hypophyseal
portal system
• Primary capillary
plexus
• Hypophyseal
portal veins
• Secondary
capillary plexus
GH, TSH, ACTH,
FSH, LH, PRL
Anterior lobe
of pituitary
A portal
system is
two
capillary
plexuses
(beds)
connected
by veins.
Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2).
Hypothalamus
Anterior lobe
of pituitary
Superior
hypophyseal
artery
2 Hypothalamic hormones
travel through portal veins to
the anterior pituitary where
they stimulate or inhibit
release of hormones made in
the anterior pituitary.
GH, TSH, ACTH,
FSH, LH, PRL
Anterior lobe
of pituitary
Hypothalamic
neurons synthesize
GHRH, GHIH, TRH,
CRH, GnRH, PIH.
1 When appropriately stimulated,
hypothalamic neurons secrete
releasing or inhibiting hormones
into the primary capillary plexus.
Hypophyseal
portal system
• Primary capillary
plexus
• Hypophyseal
portal veins
• Secondary
capillary plexus
A portal
system is
two
capillary
plexuses
(beds)
connected
by veins.
Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2).
Hypothalamus
Anterior lobe
of pituitary
Superior
hypophyseal
artery
2 Hypothalamic hormones
travel through portal veins to
the anterior pituitary where
they stimulate or inhibit
release of hormones made in
the anterior pituitary.
3 In response to releasing
hormones, the anterior
pituitary secretes hormones
into the secondary capillary
plexus. This in turn empties
into the general circulation.
GH, TSH, ACTH,
FSH, LH, PRL
Anterior lobe
of pituitary
Hypothalamic
neurons synthesize
GHRH, GHIH, TRH,
CRH, GnRH, PIH.
1 When appropriately stimulated,
hypothalamic neurons secrete
releasing or inhibiting hormones
into the primary capillary plexus.
Hypophyseal
portal system
• Primary capillary
plexus
• Hypophyseal
portal veins
• Secondary
capillary plexus
A portal
system is
two
capillary
plexuses
(beds)
connected
by veins.
POSTERIOR PITUITARY AND HYPOTHALAMIC
HORMONES

Oxytocin and ADH
 Each
composed of nine amino acids
 Almost identical – differ in two amino acids
OXYTOCIN
Strong stimulant of uterine contraction
 Released during childbirth
 Hormonal trigger for milk ejection
 Acts as neurotransmitter in brain

ADH (VASOPRESSIN)
Inhibits or prevents urine formation
 Regulates water balance
 Targets kidney tubules  reabsorb more water
 Release also triggered by pain, low blood
pressure, and drugs
 Inhibited by alcohol, diuretics
 High concentrations  vasoconstriction

ADH

Diabetes insipidus
 ADH
deficiency due to hypothalamus or posterior
pituitary damage
 Must keep well-hydrated

Syndrome of inappropriate ADH secretion
(SIADH)
 Retention
of fluid, headache, disorientation
 Fluid restriction; blood sodium level monitoring
ANTERIOR PITUITARY HORMONES
Growth hormone (GH)
 Thyroid-stimulating hormone (TSH) or
thyrotropin
 Adrenocorticotropic hormone (ACTH)
 Follicle-stimulating hormone (FSH)
 Luteinizing hormone (LH)
 Prolactin (PRL)

ANTERIOR PITUITARY HORMONES
All are proteins
 All except GH activate cyclic AMP secondmessenger systems at their targets
 TSH, ACTH, FSH, and LH are all tropic
hormones (regulate secretory action of other
endocrine glands)

GROWTH HORMONE (GH, OR SOMATOTROPIN)
Produced by somatotropic cells
 Direct actions on metabolism

 Increases
blood levels of fatty acids; encourages
use of fatty acids for fuel; protein synthesis
 Decreases rate of glucose uptake and metabolism
– conserving glucose
  Glycogen breakdown and glucose release to
blood (anti-insulin effect)
GROWTH HORMONE (GH, OR SOMATOTROPIN)
Indirect actions on growth
 Mediates growth via growth-promoting proteins
– insulin-like growth factors (IGFs)
 IGFs stimulate

 Uptake
of nutrients  DNA and proteins
 Formation of collagen and deposition of bone
matrix

Major targets—bone and skeletal muscle
GROWTH HORMONE (GH)

GH release chiefly regulated by hypothalamic
hormones
 Growth
hormone–releasing hormone (GHRH)
 Stimulates
release
 Growth
hormone–inhibiting hormone (GHIH)
(somatostatin)
 Inhibits

release
Ghrelin (hunger hormone) also stimulates
release
HOMEOSTATIC IMBALANCES OF GROWTH
HORMONE

Hypersecretion
 In
children results in gigantism
 In adults results in acromegaly

Hyposecretion
 In
children results in pituitary dwarfism
Figure 16.6 Growth-promoting and metabolic actions of growth hormone (GH).
Feedback
Inhibits GHRH release
Stimulates GHIH release
Anterior
pituitary
Hypothalamus
secretes growth
hormone–releasing
hormone (GHRH), and
GHIH (somatostatin)
Inhibits GH synthesis
and release
Growth hormone (GH)
Indirect actions
Direct actions
(growthpromoting)
(metabolic,
anti-insulin)
Liver and
other tissues
Produce
Insulin-like growth
factors (IGFs)
Effects
Effects
Skeletal
Extraskeletal
Fat
metabolism
Carbohydrate
metabolism
Increases, stimulates
Reduces, inhibits
Increased cartilage
formation and
skeletal growth
Increased protein
synthesis, and
cell growth and
proliferation
Increased
fat breakdown
and release
Increased blood
glucose and other
anti-insulin effects
Initial stimulus
Physiological response
Result
Figure 16.7 Disorders of pituitary growth hormone.
THYROID-STIMULATING HORMONE
(THYROTROPIN)
Produced by thyrotropic cells of anterior
pituitary
 Stimulates normal development and secretory
activity of thyroid
 Release triggered by thyrotropin-releasing
hormone from hypothalamus
 Inhibited by rising blood levels of thyroid
hormones that act on pituitary and
hypothalamus

Figure 16.8 Regulation of thyroid hormone secretion.
Hypothalamus
TRH
Anterior pituitary
TSH
Thyroid gland
Thyroid
hormones
Target cells
Stimulates
Inhibits
ADRENOCORTICOTROPIC HORMONE
(CORTICOTROPIN)
Secreted by corticotropic cells of anterior
pituitary
 Stimulates adrenal cortex to release
corticosteroids

ADRENOCORTICOTROPIC HORMONE
(CORTICOTROPIN)

Regulation of ACTH release
 Triggered
by hypothalamic corticotropin-releasing
hormone (CRH) in daily rhythm
 Internal and external factors such as fever,
hypoglycemia, and stressors can alter release of
CRH
GONADOTROPINS
Follicle-stimulating hormone (FSH) and
luteinizing hormone (LH)
 Secreted by gonadotrophs of anterior pituitary
 FSH stimulates gamete (egg or sperm)
production
 LH promotes production of gonadal hormones
 Absent from the blood in prepubertal boys and
girls

GONADOTROPINS

Regulation of gonadotropin release
 Triggered
by gonadotropin-releasing hormone
(GnRH) during and after puberty
 Suppressed by gonadal hormones (feedback)
PROLACTIN (PRL)
Secreted by prolactin cells of anterior pituitary
 Stimulates milk production
 Role in males not well understood

PROLACTIN (PRL)

Regulation of PRL release
 Primarily
controlled by prolactin-inhibiting hormone
(PIH) (dopamine)
Blood levels rise toward end of pregnancy
 Suckling stimulates PRL release and promotes
continued milk production
 Hypersecretion causes inappropriate lactation,
lack of menses, infertility in females, and
impotence in males
