Endocrine Glands

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Chapter 18

• Endocrine Glands

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Chapter 18 Outline

• Fxns of the Endocrine System
• Pituitary Gland Hypothalamus
• Thyroid Gland
• Parathyroid Glands
• Adrenal Glands
• Pancreas
• Hormonal regulation of nutrients
• Hormones of the reproductive system
• Hormones of the pineal body
• Hormones of the Thymus
• Hormones of the GI tract
• Hormone-like Substances
• FX of aging on the endocrine system

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I. Fxns of the Endocrine System (ES)
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I. Fxns of the Endocrine System

• Information needed to understand ESs regulation
  of body fxns
• Anatomy of each gland its location
• Hormones secreted by each gland
• Target tissues their responses to the hormone
• Regulation of those hormones secretion
• Consequences causes of hypersecretion/hyposecret
  ion of the hormone

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I. Fxns of the Endocrine System

• Main regulatory fxns of the ES

• Metabolism tissue maturation
• Ion regulation
• Water Balance
• Immune System regulation
• Heart rate BP regulation
• Control of bld glucose other nutrients
• Control of reproductive fxns
• Uterine contractions milk release

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I. Fxns of the Endocrine System

• Main regulatory fxns of the ES

• Metabolism tissue maturation
• Regulated rate of metabolism
• Influences the maturation of tissues (i.e.
  nervous system)
• Ion regulation
• Regulate blood pH
• Na, K, Ca in blood
• Water Balance
• Controlling solute in the blood
• Immune System regulation
• Controlling the prodn of immune cells

• Heart rate BP regulation
• Helps to prep the body for physical activity
• Control of bld glucose other nutrients
• In the bld
• Control of reproductive fxns
• Controls the development fxns of reproductive
  system in both males females
• Uterine contractions milk release
• During childbirth after birth

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II. Pituitary Gland Hypothalamus
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II. Pituitary Gland Hypothalamus

• Pituitary Gland
• Secretes 9 major hormones that regulate numerous
  body fxns secretory activities of other glands
• Hypothalamus
• Major site where nervous system ES interact
• Hypo regulates secretions of the Posterior
  Pituitary
• Hormones, sensory information that enters the CNS
  emotions in turn influence the activity of the
  hypothalamus

Figure 18.1 Pg. 610
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II. Pituitary Gland Hypothalamus

• 1cm diameter, 0.5-1g, rests in sella turcica
• Divided into 2 parts
• Posterior Pituitary
• Secretions from the PP are neurohormones
• Anterior Pituitary
• 3 regions
• Pars tuberalis
• Pars intermedia
• Pars distalis
• Hormones from AP are not neurohormones

• Pg 611 Figure 18.2

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II. Pituitary Gland Hypothalamus
Pg 611 Fig 18.3

• AP
• Hypothalamohypophysial Portal System
• Extends from the hypothalamus to the AP so that
  neurohormones produced by the hypothalamus to
  stimulate or inhibit the cells of the AP
• THUS the hypothalamus controls the AP

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II. Pituitary Gland Hypothalamus
Pg 611 Figure 18.2
Inhibiting releasing hormones released by
hypothalamus

• Growth Hormone Releasing Hormone (GHRH)
• Small peptide that stimulates the secretion of
  Growth Hormone from the AP
• Growth Hormone Inhibiting Hormone/Somatostatin
  (GHIH)
• Small peptide that inhibits the secretion of
  growth hormone from AP
• Thyrotropin-releasing hormone (TRH)
• Small peptide that stimulating the secretion of
  thyroid stimulating hormone from AP
• Corticotropin-releasing Hormone (CRH)
• Peptide that stimulates the secretion of
  adrenocorticotropic hormone from AP
• Gonadotropin-releasing Hormone (GnRH)
• Small peptide that stimulates LH and FSH release
  from the AP
• Prolactin-releasing Hormone (PRL)
• Regulate the secretion of prolactin from the AP.

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II. Pituitary Gland Hypothalamus
Pg 613 Figure 18.4

• PP
• Neurohormones released from PP are not made by
  the PP. These hormones that are stored in the PP
  are originally made in the hypothalamus.
• The neurosecretory cells of the hypothalamus have
  axons that extend to the PP. Neurohomeones are
  prodd in these neurosecretory cells and travel
  via vesicle toward the axon terminal. AT the
  axon terminal they are stored in secretory
  vesicles. The axon terminals are buried in the
  PP. Action potentials cause the release of the
  neurohormones from the axon terminal so that they
  can enter the blood stream.

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II. Pituitary Gland Hypothalamus
Pg 611 Figure 18.2

• Hormones of the PP
• Antidiuretic Hormone/ Vasopressin (ADH)
• Constricts bld vessels raises BP thus
  preventing the loss of water. (prevents large
  output of urine)
• Secretion rate Ds in response to bld osmolarity
  and bd volume (osmoreceptors)
• Osmolarity ? as solute ?
• Water intake BP can change action potential
  frequency
• Oxytocin
• Primary fxns
• ?Stimulates uterine contraction
• ? Responsible for milk ejection from the breast
  by contraction of smooth muscle around alveoli of
  mammary glands
• ? Unknown fxn
• Stimulation of oxytocin release
• Stretch of the uterus, mechanical stimulation of
  the cervix, stimulation of the breast as baby
  nurses (action potentials travel from receptor up
  the spinal cord to hypothalamus ? oxytocin
  releasing hormone.

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II. Pituitary Gland HypothalamusAP

• Hormones are proteins, glycoproteins, or
  polypeptides labeled Tropic Hormones
• Transported via the cardiovascular system
• Half life of these hormones is minutes
• Bind to membrane bound receptors on target
  tissues
• Most hormones are secreted by their own separate
  cell types.

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II. Pituitary Gland HypothalamusAP-Hormones

• Growth Hormone (GH)/Somatotropin

• Bind to membrane bound receptors that
  phosphorylate intracellular proteins
• Fxns
• Stimulates growth of most tissues
• Major role in regulating growth thus help
  determine final height
• Regulation of metabolism
• ? mvmt of aa into cells
• ? lipolysis
• ? FA release from adipocytes into bld
• ? glucose synthesis in liver
• Imp. role in reg. bld nutrient levels after meals
  fasting

• Stimulus that influences GH secretion
• Low bld glucose stress? stimulation of GH
  release
• High bld Glucose ? Inhibition of glucose release
• Hormonal Regulation by neurohormones of the
  hypothalamus
• Growth Factor Releasing Hormone(GFRH) ? secretion
• Growth Factor Inhibiting Hormone (GFRH) ?
  Inhibition

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II. Pituitary Gland HypothalamusAP-Hormones

• Thyroid-Stimulating Hormone/Throtropin (TSH)

• G-protein receptors in the membrane of the
  thyroid cells respond to binding. ? cAMP ?s
  activity of phospholipase activates opening of
  Ca2 to ? Ca2 in thyroid cells
• Fxn
• Stimulate synthesis secretion of thyroid
  hormones from thyroid

• Stimulus that influences TSH secretion
• Secreted in pulsatile fashion blood levels are
  highest at night
• Very narrow homeostatic window for TSH
• Reg. of secretion of TSH
• Hypothalamus releases Thyroid-releasing hormone
  (TRH)
• TRH? binds to receptors in AP? activates
  G-proteins ? result ? TSH secretion
• Thyroid hormone levels in the blood.
• Influences both TSH TRH secretion

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II. Pituitary Gland HypothalamusAP-Hormones

• Adrenocorticotropic Hormone (ACTH) related
  substances

• Several hormones derived from proopiomelanocotin
  secreted by AP.
• (ACTH, Lipotropins, b Endorphins, Melanocyte
  stimulating hormone (MSH)
• Increased levels of release in response to stress
  exercise

• ACTH
• Binds to membrane-bound receptor ? activation of
  G-protein ? response
• Increases hormone secretion? adrenal cortex ?
  cortisol
• ACTH MSH ? bind melanocytes and increase skin
  pigmentation.

• b- endorphins
• ? in response to stress exercise
• Same FX as opiates (analgesics)
• Other proposed fxns regulation of
• Body temp, Food intake, H2O balance

• MSH
• Binds to membrane-bound receptor on melanocytes?
  stimulation of melanin deposition in skin
• Regulation not well understood

Lipotropins Bind to membrane bound receptors in
adipocytes ? cause fat brkdwn release of FAs
into circulatory system
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II. Pituitary Gland Hypothalamus AP-Hormones

• Follicle-stimulating Hormone (FSH)
• Luteinizing Hormone (LH) Prolactin

• A.k.a. Gonadotropins
• Glycoprotein hormones capable of promoting growth
  fxn of gonads
• All play a role in reproduction regulation
• All released from AP

• LH FSH
• Bind to membrane-bound receptors that are
  G-proteins
• Increase intracellular synthesis of cAMP
• Stimulate prod of gametes
• Sperm in testes
• Oocytes in ovaries
• Control prod of reproductive hormones
• Estrogens progesterone in ovaries
• Testosterone in testes
• Regulation
• Hypothalamus
• Gonadotropin releasing hormone (GnRH)
• Leutinizing Hormone releasing hormone (LHRH)

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II. Pituitary Gland Hypothalamus AP-Hormones

• Follicle-stimulating Hormone (FSH)
• Luteinizing Hormone (LH) Prolactin

• A.k.a. Gonadotropins
• Glycoprotein hormones capable of promoting growth
  fxn of gonads
• All play a role in reproduction regulation
• All released from AP

• Prolactin
• Role in milk prodn in the mammary glands of
  lactating females
• Binds to membrane-bound receptor that is bound to
  kinase? phosphorylates intracellular proteins
• Enhance progesterone secretion of ovary after
  ovulation
• Males unknown
• Regulation
• Hypothalamus neurohormones
• Prolactin Releasing Hormone (PRH)
• Prolactin-Inhibiting Hormone (PIH)

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III. Thyroid Gland
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III. Thyroid Gland
Pg 620 Figure 18.8

• Location
• Lateral upper portion of the trachea just
  inferior to the larynx
• One of the largest endocrine glands _at_ 20g
• Highly Vascular with numerous follicles whose
  centers are filled w/proteins called Thyroglobin
  (Prodd by follicular cells)
• Follicles store large amounts of thyroid hormones
  as part of thyroglobin (T3 T4)
• Parafollicular cells prod calcitonin

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III. Thyroid GlandThyroid Hormones

• 2 types

Triiodothyronine T3
Tetraiodothyronine T4

• 10 of thyroid product

• A.k.a. Thyroxine
• 90 of thyroid product

• XS thyroid hormone is stored w/in the follicles
• TSH causes the release of T3 T4 from follicles
• Major component of T3 T4 is iodine wh/is why it
  is so important to have in your diet.
• These are also lipid soluble hormones
• 70-75 in blood must be bound to transport
  protein called Thyroxine-binding protein
• Creates a large reservoir of T3 T4.
• 33-44 of the T3 is converted into T4 in the
  tissues b/c T3 is major hormone that interacts
  with target is several times more potent.
• Rapidly metabolized and excreted in urine or bile

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III. Thyroid GlandThyroid Hormones

• Mechanism of Action

• Structure
• aa derivative
• Target Tissue
• Most cells of the body
• Response
• Increased metabolic rate
• ? rate at wh/ glucose, fat protein are
  metabolized
• Increased Na-K pump activity
• Can alter activity of mitochondria
• Essential for normal process of growth
  maturation

• Intracellularly diffuse thru the PM enter nuclei
  bind to receptor molecules.
• This receptor-hormone complex interacts with DNA
  to regulate gene expression
• Final action can take up to 1 week before result
  is seen.

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III. Thyroid GlandCalcitonin

• Prodd by parafollicular cells (C-cells)
• Controlled by Ca2 levels in the Bld
• ? Ca2 in the blood ?s calcitonin prodn
• Target Bone tissue
• Binds to membrane bound receptors
• Decreases osteoclast activity
• Lengthens life of osteoblasts
• Result
• Decreased bld Ca2 phosphate
• Increased bone deposition

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IV. Parathyroid Glands
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IV. Parathyroid Glands

• 4 small units embedded in the back of the thyroid
• 2 cell Types
• Chief Cells
• Secrete parathyroid hormone (PTH)
• Oxyphils
• Unknown fxn

Figure 18.11
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IV. Parathyroid Glands

• PTH
• Structurally
• Polypeptide
• Target Tissues
• Bone, Kidneys, Small Intestine
• Response
• Increased rate of breakdown of bone by
  osteoclasts
• Increased reabsorption of Ca2 by kidneys
• Increased absorption of Ca2 by small intestine
• Increased Vit D synthesis
• Increased bld Ca2 levels

Figure 18.11
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V. Adrenal Glands
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V. Adrenal Glands

• Located above the kidney surrounded by abundant
  adipose tissue CT capsule w/an abundant blood
  supply.
• 2 major regions
• Cortex
• Outer edge
• 3 layers
• Zona glumerulosa (outer)
• Zona fasiculata (middle)
• Zona reticularis (inner)
• Medulla
• Inner core

• Each of the regions layers is fxnally
  structurally specialized

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V. Adrenal Glands

• Adrenal Medulla

• Hormones
• Epinephrine primarily norepinephrine
• ½ life of minutes
• Structure
• AA derivatives
• Target Tissue
• Heart, blood vessels, liver, fat cells
• Response
• Increased cardiac output
• Increased bld flow to skeletal muscle heart
• Vasoconstriction of bld vessels
• Visceral organs skin
• Increased release of glucose FA in the bld
• Preparation for physical activity

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V. Adrenal GlandsAdrenal Cortex

• 3 types of steroid hormones are prodd here
• All have similar structure to steroids are
  derived from cholesterol
• B/c they are lipid soluble
• They are not stored in the cell but synthesized
  as needed
• Transported in the blood via transport proteins
• Metabolized in the liver excreted in bile
  urine
• Bind to intracellular receptors to stimulate the
  synthesis of specific proteins responsible for
  proding cellular responses

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V. Adrenal GlandsAdrenal Cortex

• Hormones are made as needed not stored
• Zona Glomerulosa
• Mineralcorticoids
• Zona Faciculata
• Glucocorticoids
• Zona Reticularis
• Adrenal Androgens

• Hormones are made as needed not stored

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V. Adrenal GlandsAdrenal Cortex

• Zona Glomerulosa
• Outer section
• Mineralcorticoids (cortisol)
• Structure
• steroids
• Target Tissue
• Most tissues
• Response
• ? protein fat brkdwn
• Increased glucose prodn
• Inhibition of the immune response decreased
  inflammation

• Zona Faciculata
• Middle Layer
• Glucocorticoids
• Structure
• Steroids
• Target Tissue
• Kidney
• Response
• Increase Na K and H excretion
• Enhances water reabsorption

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V. Adrenal GlandsAdrenal Cortex

• Zona Reticularis
• Adrenal Androgens
• Structure
• steroids
• Target Tissue
• Many Tissues
• Response
• Minor importance in males
• In females
• Development of some 2ndary sex characteristics
• Axillary pubic hair

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V. Adrenal GlandsAdrenal Cortex

• Stress/Low bld glucose
• ?
• Hypothalamus releases Corticotropin Releasing
  Hormone (CRH)
• ?
• CRH goes to AP which released ACTH
• ?
• Binds to membrane-bound receptors of the adrenal
  cortex
• ?
• Stimulates the secretion of glucocorticoids,
  primarily cortisol
• (Negative Feedback for CRH)
• ?
• ? protein fat brkdwn
• Increased glucose prodn
• Inhibition of the immune response decreased
  inflammation

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VI. Pancreas

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VI. Pancreas

• Lies btwn the greater curvature if the stomach
  duodenum (beginning of the small intestine)
• Head lies close to the duodenum
• Body extends toward spleen
• Fxns as both an endocrine and exocrine gland
• Exocrine
• Acini cells prod pancreatic juice a duct which
  carries the pancreatic juice into the small
  intestine

Pg 634 Fig 18.16

• Endocrine
• Pancreatic islets secrete hormones into the
  circulatory system

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VI. Pancreas

• Pancreatic Islets
• Alpha (a) cells
• Secrete glucagon
• Small peptide hormone
• 20 of cells
• Beta (b) cells
• Secrete insulin
• Small protein w/2 polypeptide chains
• 75 of cells
• Delta (d) cells
• Secrete somatostatin
• Small polypeptide hormone
• Remaining 5 of cells

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VI. Pancreas
Cell Type a-cells
Structure Polypeptide
Hormone Glucagon
Target Tissues

• Liver

• Skeletal muscle
• Cardiac muscle
• Cartilage
• Bone
• Fibroblasts
• Leukocytes
• Mammary glands

Nervous System
Adipose Cells
Response

• No effect

• Rapid increase in breakdown of glycogen into
  glucose (glycogenolysis) release of glucose into
  the bld.
• Increased formation of glucose from aas to
  some degree from fats
• Increased metabolism of FAs resulting in
  increased ketones in the bld

• High s cause the breakdown of fats
  (lipolysis)
• Probably unimportant under most conditions

• Little effect

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VI. Pancreas
Cell Type b-cells
Structure Protein
Hormone Insulin
Target Tissues
Nervous System
Adipose Cells

• Liver

• Skeletal muscle
• Cardiac muscle
• Cartilage
• Bone
• Fibroblasts
• Leukocytes
• Mammary glands

Response

• Increased glucose uptake glycogen syntheses
• Increased up-take of certain aas

• Increased glycogen synthesis
• Increased Glycolysis

• Increased
• Glucose uptake
• Glycogen synthesis
• Fat synthesis
• FA uptake
• Glycolysis

• Little effect except to increase glucose uptake
  in the satiety center

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VI. Pancreas
Cell Type d-cells
Structure Peptide
Hormone Somatostatin

• Target Tissue
• Pancreas a b Cells
• Response
• Inhibition of insulin glucagon secretion

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VI. Pancreas

• Insulin secretion control
• Inhibition
• Low blood glucose
• Somatostation
• Secretion
• High blood glucose
• Certain aas stimulate b-cells directly
• Stimulation of PNS caused and increase in blood
  glucose causing stimulation of insulin release
• GI hormones involved in digestion regulation
  increase insulin secretion

• Glucagon secretion control
• Inhibition
• High blood glucose
• Secretion
• Low blood glucose
• Certain aas can increase glucagon secretion
• Sympathetic stimulation

• After a high protein meal both insulin glucagon
  increase
• Insulin increased uptake of aas into the cell
  for protein synthesis
• Glucagon increased process of glucose synthesis
  from aas in the liver

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VII. Hormonal Regulation of Nutrients
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VII. Hormonal Regulation of Nutrients
Pg 639
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VII. Hormonal Regulation of Nutrients
Pg 640
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VIII. Hormones of the Reproductive System
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VIII. Hormones Reproductive System

• Both reproductive organs are controlled by FSH
  LH released by the AP (also considered part of
  the Reproductive System)

Pg 461

• Placenta
• During 1st 1/3 of pregnancy it secretes an
  LH-like substance to maintain pregnancy
• Ovaries placenta ? secrete increasing amounts
  of estrogen progesterone wh/ are necessary to
  maintain pregnancy

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IX. Hormones of the Pineal Body
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IX. Hormones of the Pineal Body
Fxn of PB in Humans is still actually unclear but
when there are tumors 1. early sexual development
or 2. retarded development of reproductive system
Pg 642
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X. Thymus
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X. Thymus

• Hormone
• Thymosin
• Structure
• Peptide
• Target Tissue
• Immune Tissues
• Fxn
• Important role in development maturation of the
  immune system

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XI. Hormones of the GI-tract

• There are several they relate to digestive fxns
  by influencing the activity of the stomach,
  intestine, liver, pancreas

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XII. Hormone like substances
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XII. Hormone like Substances

• Autocrine chemical signals are released by cells
  the influence the same cell type which released
  them.
• Paracrine chemical signals are released from 1
  cell type, diffuse short distance, influence
  the activity of another cell type near by.
• Not secreted from discrete endocrine glands
• Have local FX rather than systemic FX
• Have fxns that are not understood adequately to
  explain their role in the body

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XII. Hormone like substances

• of hormone like substances listed are minimal
  there are actually tons
• Chemical communication among cells in the body
  is complex, well developed, necessary for
  maintenance of homeostasis
• Investigations increase knowledge of body fxns
  that can be used to develop techniques for
  treatment of pathologic conditions

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XIII. FX of aging on Endocrine System

• Gradual decrease in secretion rate of most, but
  not all, hormones
• Some decreases are 2ndary to gradual decreases in
  physical activity
• GH
• Decreases w/ age but it is most drastic in people
  who do not exercise
• Melatonin
• Decreases and may help to explain the changes
  seen in sleeping pattern w/age