Ch 16_lecture pt a_sp2014

CHAPTER 16: THE ENDOCRINE SYSTEM

© 2013 Pearson Education, Inc.


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



• 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



• Exocrine glands – ‘exo’ - out– Release nonhormonal substances (sweat,

saliva) – to the outside or into body cavities– Have ducts to carry secretion to membrane

surface• Endocrine glands – endo = within, crine =

excrete– Produce hormones– Lack ducts, release hormones via diffusion or

exocytosis, into blood vessels or lymphatic system



• Endocrine glands: pituitary, thyroid, parathyroid, adrenal, and pineal glands

• Hypothalamus is a neuroendocrine organ – because it

has both neural functions, as well as produces and releases hormones

• Glands that have both exocrine and endocrine functions– Pancreas, gonads, placenta

• Other tissues and organs that produce hormones– Adipose cells – release leptin– Thymus releases thymic hormones– Cells in the walls of the small intestine, stomach,

kidneys, and heart. • Recall ANP?

See page 622, Table 16.5



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)


Chemical Messengers• Hormones: long-distance chemical

signals; travel in blood or lymph

• Autocrines and paracrines are local, i.e., short-distance chemical messengers

• Some endocrinologists do not consider autocrines and paracrines as part of endocrine system.

• Autocrines: chemicals that exert effects on same cells that secrete them– E.g., prostaglandins released by smooth

muscle cells, cause contraction of those cells• Paracrines: locally acting chemicals that

affect cells other than those that secrete them– e.g., somatostatin, released by certain

pancreatic cells, stops other pancreatic cells from releasing insulin.



Mechanisms of Hormone Action

• Though hormones circulate all over, only cells with receptors for that hormone are affected.

• Target cells– Tissues with receptors for specific hormone

• Hormones alter target cell activity – they increase or decrease the rates of cellular processes.



• Hormone action on target cells may be to– Change the 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

IMPORTANT!


Chemistry of Hormones

• Two main classes– Amino acid hormones

• Water-soluble - except for thyroid hormone• Recall that amino acids are the building blocks of

protein molecules • Amino acid derivatives, peptides, and proteins

– Steroids – body makes these from cholesterol • Lipid soluble• Of the hormones produced by the major endocrine

organs - only the gonadal and adrenocortical hormones are steroids.



• Hormones act at cell receptors in one of two ways, depending on their chemical nature and receptor location– water vs. lipid– Outside vs. inside1.Water-soluble hormones (all amino acid–based

hormones except thyroid hormone)• Act on plasma membrane receptors on the outside

of the cell.• Act via G protein second messengers• Cannot enter cell



2. Lipid-soluble hormones (steroid and thyroid hormones)• Act on intracellular receptors that directly activate

genes• Can diffuse into the cell – recall that the cell

membrane is a lipid bi-layer.


Slide 1Figure 16.2 Cyclic AMP second-messenger mechanism of water-soluble hormones.

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


Plasma Membrane Receptors and Second-messenger Systems • cAMP signaling mechanism:

1. Hormone (first messenger) binds to receptor2. Receptor activates G protein inside the cell3. G protein activates adenylate cyclase4. Adenylate cyclase converts ATP to cAMP

(second messenger) 5. cAMP activates enzymes (protein kinases)

that triggers the cell to perform – i.e., secrete cellular substances, activate enzymes, or open/close ion channels.


Plasma Membrane Receptors and Second-messenger 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 – meaning that a single hormone (1st messenger) binding to one receptor can produce millions of product molecules.

• Examples of cAMP signalling:– Thyroid-Stimulating Hormone (TSH) binds to

thyroid cells to cause them to produce the hormone thyroxin

– The hormone Glucagon binds to liver cells which causes enzymes to break down glycogen molecules and release glucose to the blood.








G protein (Gs)

GDP

Receptor







Activeproteinkinase


Cytoplasm

cAMP

GTP

GTPGTP

ATP

1

2 3 4

5





Receptor G protein Enzyme 2ndmessenger Hormone (1st messenger)

binds receptor.1

Extracellular fluid

Receptor

Cytoplasm






Extracellular fluid

Hormone (1st messenger) binds receptor.1

G protein (Gs)

GDP

Receptor

GTP

GTP


2

Cytoplasm







G protein (Gs)

GDP

Receptor




Cytoplasm

GTP

GTPGTP

1

2 3







G protein (Gs)

GDP

Receptor





Cytoplasm

cAMP

GTP

GTPGTP

ATP

1

2 3 4







G protein (Gs)

GDP

Receptor







Activeproteinkinase


Cytoplasm

cAMP

GTP

GTPGTP

ATP

1

2 3 4

5

Cyclic AMP Secondary Messenger Mechanism Video


http://www.youtube.com/watch?v=Nt2r5R0ZO5U

http://www.youtube.com/watch?v=Nt2r5R0ZO5U


Other Signaling Mechanisms

• Cyclic guanosine monophosphate (cGMP) is second messenger for some hormones

• Some work without second messengers– E.g., Insulin works without a second

messenger.– The insulin receptor is tyrosine kinase. TK

provides docking sites for relay proteins which then trigger cell responses.


Intracellular Receptors and Direct Gene Activation

• Steroid hormones and thyroid hormone are lipid soluble1. Diffuse into target cells and bind with receptors inside

the cell2. Receptor-hormone complex enters nucleus; binds to

specific region of DNA3. Prompts DNA to produce messenger RNA (mRNA)4. mRNA directs protein synthesis5. These proteins 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. Slide 1

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




1

Nucleus

Receptorprotein



CytoplasmReceptor-hormonecomplex




1


Nucleus


Receptorprotein



Cytoplasm

2




1



Nucleus

DNA



Receptorprotein



Cytoplasm

2

3




1




Nucleus

mRNA

DNA



Receptorprotein



Cytoplasm

2

3

4


Slide 6Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones.


1

5




The mRNA directs protein synthesis.

New protein

Nucleus

mRNA

DNA



Receptorprotein



Cytoplasm

2

3

4

Lipid soluble proteins action video


http://www.youtube.com/watch?v=m43jBFNL7gY

http://www.youtube.com/watch?v=m43jBFNL7gY


Target Cell Specificity

• Target cells must have specific receptors to which hormone binds, for example– ACTH receptors are found only on certain

cells of adrenal cortex– Thyroxin receptors are found on nearly all

cells of body because thyroxin is the main hormone that stimulates cell metabolism.


Target Cell Activation

• Target cell activation depends on three factors– Blood levels of hormone– Relative number of receptors on, or in, the

target cell– Affinity of binding between receptor and

hormone, i.e,, how ‘strong’ is the bond between the receptor and the hormone.


Target Cell Activation

• Hormones can influence the number of their receptors– Up-regulation - If hormone levels are low, the

target cells respond and form more receptors.

– Down-regulation - If hormone levels are high, the target cells respond by losing receptors


Control of Hormone Release

• Blood levels of hormones– Controlled by negative feedback systems– Vary only within narrow, desirable range

• Endocrine gland is 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. Slide 1

Humoral StimulusHormone 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+.




Parathyroidglands

Parathyroidglands

Capillary (low Ca2+

in blood)





Stimulus: Low concentration of Ca2+ incapillary blood.

Parathyroidglands

Parathyroidglands

Capillary (low Ca2+

in blood)


PTH

Response: Parathyroid glands secreteparathyroid hormone (PTH), whichincreases blood Ca2+.

Figure 11.2

Central nervous system (CNS)Brain and spinal cordIntegrative and control centers

Peripheral nervous system (PNS)Cranial nerves and spinal nervesCommunication lines between theCNS and the rest of the body

Parasympatheticdivision

Conserves energyPromotes house-keeping functionsduring rest

Motor (efferent) divisionMotor nerve fibersConducts impulses from the CNSto effectors (muscles and glands)

Sensory (afferent) divisionSomatic and visceral sensorynerve fibersConducts impulses fromreceptors to the CNS

Somatic nervoussystem

Somatic motor(voluntary)Conducts impulsesfrom the CNS toskeletal muscles

Sympathetic divisionMobilizes bodysystems during activity

Autonomic nervoussystem (ANS)

Visceral motor(involuntary)Conducts impulsesfrom the CNS tocardiac muscles,smooth muscles,and glands

StructureFunctionSensory (afferent)division of PNS Motor (efferent) division of PNS

Somatic sensoryfiber

Visceral sensory fiber

Motor fiber of somatic nervous system

Skin

Stomach Skeletalmuscle

Heart

BladderParasympathetic motor fiber of ANS

Sympathetic motor fiber of ANS

Figure 11.2


Neural Stimuli

• Nerve fibers stimulate hormone release– Sympathetic nervous system fibers stimulate

adrenal medulla (of the adrenal gland) to secrete catecholamines (e.g., epinephrine and norepinephrine – act like chemical transmitters)

- norepinephrine, aka, noradrenalinepinephrine, and epinephrine, aka adrenaline – ‘fight or flight’ chemicals


Figure 16.4b Three types of endocrine gland stimuli. Slide 1

Neural StimulusHormone 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.




CNS (spinal cord)



Capillary




Stimulus: Action potentials in preganglionicsympathetic fibers to adrenal medulla.

CNS (spinal cord)



Capillary

Response: Adrenal medulla cells secreteepinephrine and norepinephrine.


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.

Is this a negative or positive feedback loop?


Figure 16.4c Three types of endocrine gland stimuli. Slide 1

Hormonal StimulusHormone 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.





Thyroidgland

Adrenalcortex

Gonad(Testis)

Hypothalamus




Stimulus: Hormones from hypothalamus.


Thyroidgland

Adrenalcortex

Gonad(Testis)

Hypothalamus

Response: Anterior pituitary gland secreteshormones that stimulate other endocrine glands to secrete hormones.


Nervous System Modulation

• Nervous system modifies stimulation of endocrine glands and their negative feedback mechanisms – Example: under severe stress, the hypothalamus and

sympathetic nervous system are activated • causes body glucose levels to rise to get your

body ready to react. • Nervous system can override normal endocrine

controls – Can turn on humoral, hormonal and neural stimuli– Can turn off stimuli via feedback mechanism– Maintains homeostasis by making adjustments


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 tissue– Anterior pituitary (lobe)

(adenohypophysis)• Glandular tissue


Pituitary-hypothalamic Relationships

• Posterior pituitary (lobe)– Is derived from neural tissue of the

hypothalamus– Is connected to the hypothalamus via the

hypothalamic-hypophyseal tract– The neurohormones oxytocin and

antidiuretic hormone (ADH), are synthesized by nuclei in the hypothalamus

– 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).Slide 1

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 Optic

chiasma

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.




1


chiasma


Axon terminals


Hypothalamus

Supraopticnucleus


Hypothalamic-hypophyseal

tract





1

2


chiasma


Axon terminals


Hypothalamus

Supraopticnucleus


Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary.Hypothalamic-

hypophysealtract






1

2

3


chiasma


Axon terminals


Hypothalamus

Supraopticnucleus



hypophysealtract






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


chiasma


Axon terminals


Hypothalamus

Supraopticnucleus



hypophysealtract



Pituitary-hypothalamic Relationships

• Anterior Lobe:– Originates as outpocketing 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). Slide 1

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


Hypothalamus Hypothalamicneurons synthesizeGHRH, GHIH, TRH,CRH, GnRH, PIH.

A portal system is two capillary plexuses (beds) connected by veins.

12

3








Superiorhypophyseal

artery




1









Superiorhypophyseal

artery




12




In response to releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus. This in turn empties into the general circulation.






Superiorhypophyseal

artery




12

3


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 (including large loss of blood from injury, and drugs)

• Inhibited by alcohol, diuretics• At high concentrations, ADH causes

vasoconstriction


ADH

• Diabetes insipidus– ADH deficiency due to hypothalamus or

posterior pituitary damage– Must keep well-hydrated

• Syndrome of inappropriate ADH secretion (SIADH)– High ADH levels– Retention of fluid, headache, disorientation– Treatment includes 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 second-

messenger 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 (occurs after

the epiphyseal plate closure at puberty)• 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 releaseStimulates GHIH release

Inhibits GH synthesisand release

Feedback

Indirect actions(growth-promoting)

Liver andother tissues

Insulin-like growthfactors (IGFs)

Produce

Effects

Skeletal Extraskeletal Fatmetabolism

Carbohydratemetabolism

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.


Examples of Acromegaly – caused by hypersecretion of Growth Hormone (GH)


Thyroid-stimulating Hormone (TSH , aka 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


Hypothalamus

TRH

Anterior pituitary

TSH

Thyroid gland

Thyroidhormones

Target cells Stimulates

Figure 16.8 Regulation of thyroid hormone secretion.

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 gonadotropic cells 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)

Progesterone

• hormone secreted by the female reproductive system that functions mainly to regulate the condition of the inner lining (endometrium) of the uterus

• produced by the ovaries, placenta, and adrenal glands.


Estrogen

• Also known as oestrogen

• the primary female sex hormone

• responsible for development and regulation of the female reproductive system and secondary sex characteristics


Testosterone

• is secreted primarily by the testicles of males and, to a lesser extent, the ovaries of females.

• plays a key role in the development of male reproductive tissues such as the testis and prostate as well as promoting secondary sexual characteristics such as increased muscle, bone mass, and the growth of body hair


https://en.wikipedia.org/wiki/Testicles

https://en.wikipedia.org/wiki/Male

https://en.wikipedia.org/wiki/Ovaries

https://en.wikipedia.org/wiki/Female

https://en.wikipedia.org/wiki/Testis

https://en.wikipedia.org/wiki/Prostate

https://en.wikipedia.org/wiki/Muscle

https://en.wikipedia.org/wiki/Bone

https://en.wikipedia.org/wiki/Androgenic_hair


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

Ch 16_lecture pt a_sp2014

Healthcare

Transcript of Ch 16_lecture pt a_sp2014