ENDOKRIN KULIAH FKG

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    ENDOCRINOLOGYThe Scientific Study of the Endocrine

    Glands and their Hormones

    Picture : Insulin-containing cells on direct immunofluorescence of islets of Langerhans

    MIFTAHRACHMAN, DR, SPPD-MKES

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    Outline Lecture 1

    General Features of the Endocrine System

    and Important definitions

    Evolution of the Endocrine System

    Classes of Hormones

    Actions of Hormones

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    General Features of theEndocrine System

    Endocrine glands are :

    - ductless

    - have a rich supply of blood.Hormones, produced by the endocrine glands are

    secreted into the bloodstream.

    Hormones travel in the blood to target cells closeby or far away from point of secretion.

    Hormones receptors are specific binding sites onthe target cell.

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    Important Definitions

    What are hormones?- Hormones are organic chemical messengers produced

    and secreted by endocrine cells into the bloodstream.

    - Hormones regulate, integrate and control a wide rangeof physiologic functions.

    Silverthorn, Human Physiology, 3rd

    edition Figure 6-1&2

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    Important Definitions Cont.

    What are endocrine glands?

    Endocrine glands are ductless glands comprised of endocrine cells.

    This means that these glands do not have ducts that lead to the outsideof the body.

    For example, sweat glands are NOT endocrine glands(they are insteadexocrine glands) because sweat glands have ducts that lead to theoutside surface of your skin (thats how the sweat gets out).

    The fact that endocrine glands are ductless means that these glandssecrete hormones directly into the blood stream (instead of to theoutside of your body).

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    Important Definitions Cont.

    What are target cells?Target cells refer to cells that contain specific receptors

    (binding sites) for a particular hormone.

    Once a hormone binds to receptors on a target cell, a

    series of cellular events unfold that eventually impactgene expression and protein synthesis.

    Silverthorn, Human Physiology, 3rd

    edition Figure 6-1&2

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    Important Definitions Cont.

    What are hormone receptors?

    Hormone receptors are binding sites on the target cell

    (either on the surface or in the cytoplasm or nucleus ofthe target cell) that are activated only when specific

    hormones bind to them.

    If a hormone does not/cannot bind to its receptor, then nophysiologic effect results.

    See next slide for a picture of a hormone bound to its receptor

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    Growth hormone regulates cell growth by bindingto growth hormone receptors on target cells.

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    Hormones Cytokines GrowthfactorsProduction Only specialized

    cells

    Many cell types

    Few places Many places

    Action Long-range Mostly short-

    range

    Short-

    range

    Pleiotropy Low High Medium

    Redundance Low High Medium

    Regulation Tight Loose

    Function Homeostasis

    Ontogenesis

    Defence Remo-

    deling

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    Outline Lecture 1

    General Features of the Endocrine System

    and Important definitions

    Evolution of the Endocrine System

    Classes of Hormones

    Actions of Hormones

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    Types of humoral signalization

    Endocrine from gland via blood to a distance

    Neurocrine via axonal transport and then via blood

    Paracrine neighboring cells of different types

    Autocrine neighboring cells of the same type or thesecreting cell itself

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    Silverthorn, Human Physiology, 3rd

    edition Figure 6-1&2

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    Outline Lecture 1

    General Features of the Endocrine System

    and Important definitions

    Evolution of the Endocrine System

    Classes of Hormones

    Actions of Hormones

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    Chemical characteristicsof hormones

    Amines (from tyrosine) hydroxylation - catecholamines

    iodination - thyroid hormones Peptides/proteins

    Steroids (from cholesterol)

    adrenocortikoids sex hormones

    active metabolites of vitamin D

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    Classes of Hormones

    Steroids vs. Peptide Hormones

    Hormones fall into 2 general classes based

    on their molecular structure and synthesis.

    All steroid hormones are made initially

    from the precursor (precursor = first step inbiosynthetic pathway) cholesterol.

    See next slide for a diagram of the biosynthetic pathway of steroid hormones

    from cholesterol.

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    Steroid Hormones

    Steroid hormones are produced by thegonads and adrenal cortex.

    Thyroid hormones are not steroids, but willbe categorized with steroids for simplicity.

    Steroid hormones are made from cholesterol in

    the smooth endoplasmic reticulum and

    mitochondria of endocrine cells.

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    Steroid Hormones

    Steroid hormones cannot be stored in vesicles inthe endocrine cells that produce them.

    As soon as steroid hormones are produced, theydiffuse out of the endocrine cell and enter thebloodstream.

    Steroid hormones are lipid soluble and theirreceptors are located inside their target cell.

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    Peptide Hormones

    Peptide hormones are comprised of chains on

    amino acids.

    Like most proteins, peptide hormones aresynthesized on ribosomes of the (rough)

    endoplasmic reticulum of endocrine cells.

    Peptide hormones can be stored in vesicles in

    endocrine cells until they are needed at some

    later point.

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    Peptide Hormones

    Peptide hormones do not readily pass

    through cell membranes (lipid bilayers)

    and they are referred to as water soluble.

    Receptors for peptide hormones are found

    on the cell surface of their target cells.

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    Outline Lecture 1

    General Features of the Endocrine System

    and Important definitions

    Evolution of the Endocrine System

    Classes of Hormones

    Actions of Hormones

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    Regulation of hormone release

    Feedback Negative

    Gland Target tissue

    hormone

    product

    inhibition

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    Regulation of hormone release

    Feedback Negative

    Positive (only narrow dose range)

    Gland Target tissue

    hormone

    product

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    Regulation of hormone release

    Feedback Negative

    Positive (only narrow dose range) Nerve regulation

    pain, emotions, sex, injury, stress,...

    e.g. oxytocin with nipple stimulation

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    Combined feedbackStress etc.

    CRH secretion in hypothalamus

    ACTH secretion in pituitary

    plasma ACTH

    cortisol secretion in adrenals

    plasma cortisol

    stimulation

    inhibition

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    Regulation of hormone release

    Rhythms circadian

    light/dark fine/tune endogenous rhythm of cells &suprachiasmatic nucleus of hypothalamus

    melatonin, cortisol monthly

    seasonal (day length; atavistic)

    developmental (puberty, menopause)

    Pulsations/oscillations gonadotropins

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    Regulation of hormone release

    Rhythms circadian

    0

    100

    200

    300

    400

    500

    600

    Cortisol(nM)

    Time of day

    09 0921

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    Pulsatility inGnRH & LH release

    0

    2

    4

    6

    8

    10

    12

    14 GnRH (pg/10 min)

    LH (ng/ml)

    12:00 16:0014:00

    Time of day

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    Actions of Hormones

    Fetal development and differentiation

    Cell growth and cancer

    Metabolism

    Cardiovascular function Renal function

    Skeletal function

    Reproductive function

    Immune function

    Central nervous system function

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    Hormone production:

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    Hormone production:Less traditional sources

    Placenta:All hormones

    Adipocytes:Leptin

    Cardiocytes:ANP

    Kidney:ErythropoietinRAS

    GIT:GastrinCholecystokininSecretin,...

    Endothelium:

    EndothelinsNOProstanoids,...

    Immune system:Cytokines

    Platelets, mesenchyme:

    Growth factors

    Gonads:Inhibins

    Activins

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    THANK YOU