c h a p t e r 16 part a 1. chief complaint: 8 year old girl with excessive thirst, frequent...
TRANSCRIPT
C H A P T E R 16
Part A
1
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
At the doctor's office, blood and urine samples are taken. The following lab results are noted:
blood glucose level = 545 mg/dl (normal 50-170 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
4
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
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
Exocrine glands Nonhormonal substances (sweat, saliva) Have ducts to carry secretion to membrane
surface Endocrine glands
Produce hormones Lack ducts
Slide 3
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 glandHypothalamusPituitary gland
Thyroid glandParathyroid glands(on dorsal aspect of thyroid gland)Thymus
Adrenal glands
Pancreas
Gonads
• Testis (male)• Ovary (female)
Slide 5
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
Two main classes Amino acid-based hormones
Amino acid derivatives, peptides, and proteins Steroids
Synthesized from cholesterol Gonadal and adrenocortical hormones
Slide 7
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
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
Hormones act at receptors in one of two ways, depending on their chemical nature and receptor location1. 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
2. Lipid-soluble hormones (steroid and thyroid hormones) Act on intracellular receptors that directly
activate genes Can enter cell
Slide 11
cAMP signaling mechanism:1. Hormone (first messenger) binds to
receptor2. Receptor activates G protein3. G protein activates adenylate cyclase4. Adenylate cyclase converts ATP to cAMP
(second messenger) 5. cAMP activates protein kinases that
phosphorylate proteins
Slide 12
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
Recall from Chapter 3 thatG protein signaling mechanismsare like a molecular relay race.
Hormone(1st messenger)
Receptor G protein Enzyme 2ndmessenger
Adenylate cyclase Extracellular fluid
G protein (Gs)
GDP
Receptor
Hormone (1st messenger) binds receptor.
Receptor activates G protein (Gs).
G protein activates adenylate cyclase.
Adenylate cyclase convertsATP to cAMP (2nd messenger).
Inactiveproteinkinase
Triggers responses of target cell (activatesenzymes, stimulatescellular secretion,opens ion channel, etc.)
Activeproteinkinase
cAMP activates protein kinases.
Cytoplasm
cAMP
GTP
GTPGTP
ATP
1
2 3 4
5
Slide 14
Recall from Chapter 3 thatG protein signaling mechanismsare like a molecular relay race.
Hormone(1st messenger)
Receptor G protein Enzyme 2ndmessenger Hormone (1st messenger)
binds receptor.1
Extracellular fluid
Receptor
Cytoplasm
Slide 15
Recall from Chapter 3 thatG protein signaling mechanismsare like a molecular relay race.
Hormone(1st messenger)
Receptor G protein Enzyme 2ndmessenger
Extracellular fluid
Hormone (1st messenger) binds receptor.1
G protein (Gs)
GDP
Receptor
GTP
GTP
Receptor activates G protein (Gs).
2
Cytoplasm
Slide 16
Recall from Chapter 3 thatG protein signaling mechanismsare like a molecular relay race.
Hormone(1st messenger)
Receptor G protein Enzyme 2ndmessenger
Adenylate cyclase Extracellular fluid
G protein (Gs)
GDP
Receptor
Hormone (1st messenger) binds receptor.
Receptor activates G protein (Gs).
G protein activates adenylate cyclase.
Cytoplasm
GTP
GTPGTP
1
2 3
Slide 17
Recall from Chapter 3 thatG protein signaling mechanismsare like a molecular relay race.
Hormone(1st messenger)
Receptor G protein Enzyme 2ndmessenger
Adenylate cyclase Extracellular fluid
G protein (Gs)
GDP
Receptor
Hormone (1st messenger) binds receptor.
Receptor activates G protein (Gs).
G protein activates adenylate cyclase.
Adenylate cyclase convertsATP to cAMP (2nd messenger).
Cytoplasm
cAMP
GTP
GTPGTP
ATP
1
2 3 4
Slide 18
Recall from Chapter 3 thatG protein signaling mechanismsare like a molecular relay race.
Hormone(1st messenger)
Receptor G protein Enzyme 2ndmessenger
Adenylate cyclase Extracellular fluid
G protein (Gs)
GDP
Receptor
Hormone (1st messenger) binds receptor.
Receptor activates G protein (Gs).
G protein activates adenylate cyclase.
Adenylate cyclase convertsATP to cAMP (2nd messenger).
Inactiveproteinkinase
Triggers responses of target cell (activatesenzymes, stimulatescellular secretion,opens ion channel, etc.)
Activeproteinkinase
cAMP activates protein kinases.
Cytoplasm
cAMP
GTP
GTPGTP
ATP
1
2 3 4
5
Slide 19
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
Ca2+ alters enzyme activity and channels, or binds to regulatory protein calmodulin
Calcium-bound calmodulin activates enzymes that amplify cellular response
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
Steroid hormones and thyroid hormone1. Diffuse into target cells and bind with
intracellular receptors2. Receptor-hormone complex enters nucleus;
binds to specific region of DNA3. Prompts DNA transcription to produce
mRNA4. mRNA directs protein synthesis5. Promote metabolic activities, or promote
synthesis of structural proteins or proteins for export from cell
The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.
1
5
The receptor-hormone complex enters the nucleus.
The receptor- hormone complex binds a specific DNA region.
Binding initiates transcription of the gene to mRNA.
The mRNA directs protein synthesis.
New protein
Nucleus
mRNA
DNA
ReceptorBinding region
Receptor-hormonecomplex
Receptorprotein
Steroidhormone Plasma
membraneExtracellularfluid
Cytoplasm
2
3
4
The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.
1
Nucleus
Receptorprotein
Steroidhormone Plasma
membraneExtracellularfluid
Cytoplasm
Receptor-hormonecomplex
The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.
1
The receptor-hormone complex enters the nucleus.
Nucleus
Receptor-hormonecomplex
Receptorprotein
Steroidhormone Plasma
membraneExtracellularfluid
Cytoplasm
2
The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.
1
The receptor-hormone complex enters the nucleus.
The receptor- hormone complex binds a specific DNA region.
Nucleus
DNA
ReceptorBinding region
Receptor-hormonecomplex
Receptorprotein
Steroidhormone Plasma
membraneExtracellularfluid
Cytoplasm
2
3
The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.
1
The receptor-hormone complex enters the nucleus.
The receptor- hormone complex binds a specific DNA region.
Binding initiates transcription of the gene to mRNA.
Nucleus
mRNA
DNA
ReceptorBinding region
Receptor-hormonecomplex
Receptorprotein
Steroidhormone Plasma
membraneExtracellularfluid
Cytoplasm
2
3
4
The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.
1
5
The receptor-hormone complex enters the nucleus.
The receptor- hormone complex binds a specific DNA region.
Binding initiates transcription of the gene to mRNA.
The mRNA directs protein synthesis.
New protein
Nucleus
mRNA
DNA
ReceptorBinding region
Receptor-hormonecomplex
Receptorprotein
Steroidhormone Plasma
membraneExtracellularfluid
Cytoplasm
2
3
4
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 depends on three factors Blood levels of hormone Relative number of receptors on or in
target cell Affinity of binding between receptor and
hormone
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
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
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 alteredlevels of certain critical ions ornutrients.
Stimulus: Low concentration of Ca2+ incapillary blood.
Parathyroidglands
Parathyroidglands
Capillary (low Ca2+
in blood)
Thyroid gland(posterior view)
PTH
Response: Parathyroid glands secreteparathyroid hormone (PTH), whichincreases blood Ca2+.
Figure 16.4a Three types of endocrine gland stimuli.
Humoral Stimulus
Hormone release caused by alteredlevels of certain critical ions ornutrients.
Parathyroidglands
Parathyroidglands
Capillary (low Ca2+
in blood)
Thyroid gland(posterior view)
Figure 16.4a Three types of endocrine gland stimuli.
Humoral Stimulus
Hormone release caused by alteredlevels of certain critical ions ornutrients.
Stimulus: Low concentration of Ca2+ incapillary blood.
Parathyroidglands
Parathyroidglands
Capillary (low Ca2+
in blood)
Thyroid gland(posterior view)
PTH
Response: Parathyroid glands secreteparathyroid hormone (PTH), whichincreases blood Ca2+.
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 anotherhormone (a tropic hormone).
Stimulus: Hormones from hypothalamus.
Anteriorpituitarygland
Thyroidgland
Adrenalcortex
Gonad(Testis)
Hypothalamus
Response: Anterior pituitary gland secreteshormones that stimulate other endocrine glands to secrete hormones.
Figure 16.4c Three types of endocrine gland stimuli.
Hormonal Stimulus
Hormone release caused by anotherhormone (a tropic hormone).
Anteriorpituitarygland
Thyroidgland
Adrenalcortex
Gonad(Testis)
Hypothalamus
Figure 16.4c Three types of endocrine gland stimuli.
Hormonal Stimulus
Hormone release caused by anotherhormone (a tropic hormone).
Anteriorpituitarygland
Thyroidgland
Adrenalcortex
Gonad(Testis)
Hypothalamus
Figure 16.4c Three types of endocrine gland stimuli.
Hormonal Stimulus
Hormone release caused by anotherhormone (a tropic hormone).
Stimulus: Hormones from hypothalamus.
Anteriorpituitarygland
Thyroidgland
Adrenalcortex
Gonad(Testis)
Hypothalamus
Response: Anterior pituitary gland secreteshormones that stimulate other endocrine glands to secrete hormones.
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.
Stimulus: Action potentials in preganglionicsympathetic fibers to adrenal medulla.
CNS (spinal cord)
Preganglionicsympatheticfibers
Medulla ofadrenal gland
Capillary
Response: Adrenal medulla cells secreteepinephrine and norepinephrine.
Figure 16.4b Three types of endocrine gland stimuli.
Neural Stimulus
Hormone release caused by neural input.
CNS (spinal cord)
Preganglionicsympatheticfibers
Medulla ofadrenal gland
Capillary
Figure 16.4b Three types of endocrine gland stimuli.
Neural Stimulus
Hormone release caused by neural input.
Stimulus: Action potentials in preganglionicsympathetic fibers to adrenal medulla.
CNS (spinal cord)
Preganglionicsympatheticfibers
Medulla ofadrenal gland
Capillary
Response: Adrenal medulla cells secreteepinephrine and norepinephrine.
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 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 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
Some responses ~ immediate Some, especially steroid, hours to days Some must be activated in target cells
Limited Ranges from 10 seconds to several hours Effects may disappear as blood levels drop Some persist at low blood levels
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
Pituitary gland (hypophysis) has two major lobes Posterior pituitary (lobe)
Neural tissue Anterior pituitary (lobe)
(adenohypophysis) Glandular tissue
Posterior pituitary (lobe) Downgrowth of hypothalamic neural tissue Neural connection to hypothalamus
(hypothalamic-hypophyseal 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).
Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH).
Oxytocin and ADH are stored in axon terminals in the posterior pituitary.
When hypothalamic neurons fire, action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood.
1
2
3
4OxytocinADH
Posterior lobeof pituitary
Opticchiasma
Infundibulum(connecting stalk)
Hypothalamic-hypophyseal
tract
Axon terminals
Posterior lobeof pituitary
Paraventricular nucleus
Hypothalamus
Supraopticnucleus
Inferiorhypophysealartery
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).
Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH).
1
Posterior lobeof pituitary
Opticchiasma
Infundibulum(connecting stalk)
Axon terminals
Paraventricular nucleus
Hypothalamus
Supraopticnucleus
Inferiorhypophysealartery
Hypothalamic-hypophyseal
tract
Posterior lobeof pituitary
Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).
Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH).
1
2
Posterior lobeof pituitary
Opticchiasma
Infundibulum(connecting stalk)
Axon terminals
Paraventricular nucleus
Hypothalamus
Supraopticnucleus
Inferiorhypophysealartery
Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary.Hypothalamic-
hypophysealtract
Posterior lobeof pituitary
Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).
Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH).
Oxytocin and ADH are stored in axon terminals in the posterior pituitary.
1
2
3
Posterior lobeof pituitary
Opticchiasma
Infundibulum(connecting stalk)
Axon terminals
Paraventricular nucleus
Hypothalamus
Supraopticnucleus
Inferiorhypophysealartery
Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary.Hypothalamic-
hypophysealtract
Posterior lobeof pituitary
Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).
Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH).
Oxytocin and ADH are stored in axon terminals in the posterior pituitary.
When hypothalamic neurons fire, action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood.
1
2
3
4OxytocinADH
Posterior lobeof pituitary
Opticchiasma
Infundibulum(connecting stalk)
Axon terminals
Paraventricular nucleus
Hypothalamus
Supraopticnucleus
Inferiorhypophysealartery
Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary.Hypothalamic-
hypophysealtract
Posterior lobeof pituitary
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).
Hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary.
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 lobeof pituitary
When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus.
Hypophysealportal system
• Primary capillary plexus• Hypophyseal portal veins• Secondary capillary plexus
Superiorhypophyseal
artery
Anterior lobeof pituitary
Hypothalamus Hypothalamicneurons synthesizeGHRH, GHIH, TRH,CRH, GnRH, PIH.
A portal system is two capillary plexuses (beds) connected by veins.
12
3
Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2).
GH, TSH, ACTH,FSH, LH, PRL
Anterior lobeof pituitary
When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus.
Hypophysealportal system
• Primary capillary plexus• Hypophyseal portal veins• Secondary capillary plexus
Superiorhypophyseal
artery
Anterior lobeof pituitary
Hypothalamus Hypothalamicneurons synthesizeGHRH, GHIH, TRH,CRH, GnRH, PIH.
A portal system is two capillary plexuses (beds) connected by veins.
1
Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 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 lobeof pituitary
When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus.
Hypophysealportal system
• Primary capillary plexus• Hypophyseal portal veins• Secondary capillary plexus
Superiorhypophyseal
artery
Anterior lobeof pituitary
Hypothalamus Hypothalamicneurons synthesizeGHRH, GHIH, TRH,CRH, GnRH, PIH.
A portal system is two capillary plexuses (beds) connected by veins.
12
Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2).
Hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary.
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 lobeof pituitary
When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus.
Hypophysealportal system
• Primary capillary plexus• Hypophyseal portal veins• Secondary capillary plexus
Superiorhypophyseal
artery
Anterior lobeof pituitary
Hypothalamus Hypothalamicneurons synthesizeGHRH, GHIH, TRH,CRH, GnRH, PIH.
A portal system is two capillary plexuses (beds) connected by veins.
12
3
Oxytocin and ADH Each composed of nine amino acids Almost identical – differ in two amino acids
Strong stimulant of uterine contraction Released during childbirth Hormonal trigger for milk ejection Acts as neurotransmitter in brain
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
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
Growth hormone (GH) Thyroid-stimulating hormone (TSH)
or thyrotropin Adrenocorticotropic hormone
(ACTH) Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Prolactin (PRL)
All are proteins All except GH activate cyclic AMP
second-messenger systems at their targets
TSH, ACTH, FSH, and LH are all tropic hormones (regulate secretory action of other endocrine glands)
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)
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
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
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).
Hypothalamussecretes growthhormone–releasinghormone (GHRH), andGHIH (somatostatin)
Anteriorpituitary
Inhibits GHRH release
Stimulates GHIH release
Inhibits GH synthesisand release
Feedback
Indirect actions(growth-promoting)
Liver andother tissues
Insulin-like growthfactors (IGFs)
Produce
Effects
Skeletal ExtraskeletalFat
metabolismCarbohydratemetabolism
Direct actions(metabolic,anti-insulin)
Effects
Growth hormone (GH)
Increased cartilageformation and
skeletal growth
Increased proteinsynthesis, andcell growth and
proliferation
Increasedfat breakdown
and release
Increased bloodglucose and otheranti-insulin effects
Increases, stimulates
Initial stimulus
Reduces, inhibits
Physiological response
Result
Figure 16.7 Disorders of pituitary growth hormone.
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
Hypothalamus
TRH
Anterior pituitary
TSH
Thyroid gland
Thyroidhormones
Target cellsStimulates
Figure 16.8 Regulation of thyroid hormone secretion.
Inhibits
Secreted by corticotropic cells of anterior pituitary
Stimulates adrenal cortex to release corticosteroids
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
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
Regulation of gonadotropin release Triggered by gonadotropin-releasing
hormone (GnRH) during and after puberty Suppressed by gonadal hormones
(feedback)
Secreted by prolactin cells of anterior pituitary
Stimulates milk production Role in males not well understood
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