H' Hormones and their Actions

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H. Hormones and their Actions

• Hormone chemistry
• Hormone synthesis - SKIP
• Hormone receptors mode of action
• Enzyme amplification
• Modulation of target cell sensitivity
• Hormone Interactions
• Hormone clearance

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1. Hormone Chemistry

• Steroid hormones
• Peptide hormones
• Monoamines

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Steroid hormones

• Derived from cholesterol
• made by gonads
• estrogens
• progesterone
• testosterone
• made by adrenal cortex
• cortisol
• corticosterone
• aldosterone
• DHEA

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Peptide hormones
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Monoamines
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3. Hormone transport

• Transport proteins
• Purpose to transport hydrophobic hormones in the
  blood
• Allow them to travel in blood (water solvent)
• Protect them from enzyme degradation in blood
• Hydrophobic hormones
• Steroid hormones
• Thyroid hormone (T3 T4)
• Bound hormone bound to transport protein
• Unbound (free) hormone not bound to transport
  protein

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4. Hormone receptors and mode of action

• general info
• Structure
• Protein/glycoprotein
• Specificity recognize only one hormone
• Saturability finite number of receptors/cell
  when all are occupied by hormone molecules, no
  increase in binding can occur
• Location
• On cell membrane, nucleus, etc. of target cells
• Function
• To bind to and recognize hormone signal
• Binding ? alter target metabolism

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Steroid hormone receptors

• Hydrodrophobic
• Enter target cells thru plasma membranes
• Enter nucleus and bind to receptors on DNA
• Trigger protein synthesis in target cells
• T4 is converted to T3
• T3 binds to receptors on
• Mitochondria? ? aerobic respiration
• Ribosomes ? ? protein synthesis
• Chromatin ? transcription ? ? mRNA synthesis
• ? ? ATPase ? ? heat (calorigenic effect)

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Peptides and catecholamines

• Hydrophilic
• Bind to cell surface receptors
• Activate 2nd messenger cascades
• Intracellular events activated by a hormone can
  be different in different target cells
• ADH (different cascades in kidney vs. smooth
  muscle)

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4. Enzyme Amplification

• One molecule of hormone can activate many
  molecules of enzyme inside a target cell ? many
  more molecules of product.

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5. Modulation of target sensitivity

• Up-regulation more receptors, more sensitivity
• Down-regulation fewer receptors, less sensitivity

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6. Hormone interactions

• Synergistic hormones act together
• Permissive first hormone enhances target
  response to second hormone
• Antagonistic hormones oppose each other

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V. Stress Adaptation

• A. Introduction
• B. The Alarm Reaction
• C. The Stage of Resistance
• D. The Stage of Exhaustion

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Introduction

• Definition any situation which upsets
  homeostasis and threatens physical or emotional
  well-being
• General adaptation syndrome (GAS) (a.k.a., stress
  response)
• ? EPI, cortisol
• described in stages

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B. The Alarm Reaction

• NE (sympathetic n.s.) EPI (adrenals)
• Breakdown of stored glycogen ?? blood glucose
• ? aldosterone ? water Na retention
• ? angiotensin ? ? b.p.

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C. The Stage of Resistance

• Glycogen exhausted
• Requires alternative fuels
• Cortisol plays important role
• ? CRH ? ACTH ? ? cortisol
• Cortisol ? fat, protein, metabolism ? glycerol,
  FAs aas ? gluconeogenesis
• Protein synthesis inhibited
• Bad for immune system (cant make Abs)
• poor wound healing, etc.

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D. The Stage of Exhaustion

• Fat reserves important
• When fat depleted ? homeostasis blocked
• Protein breakdown begins ? energy
• progressive wasting
• Adrenals may fail
• No glucocorticoids ? ? gluconeogenesis
• aldosterone ? water retention, hypokalemia ?
  n.s. dysfunction, alkalosis (high blood pH), etc.
  ? potentially fatal

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VI. Eicosanoids
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VII. Endocrine Disorders

• A. Hyposecretion Hypersecretion
• B. Pituitary Disorders
• C. Thyroid Disorders
• D. Parathyroid Disorders
• E. Adrenal Disorders
• F. Diabetes Mellitus

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Hyposecretion Hypersecretion

• hyposecretion
• diabetes incipidus hyposecretion of ADH
• Hypersecretion
• pheochromocytoma
• Graves disease (toxic goiter)

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B. Pituitary Disorders

• Hypersecretion
• acromegaly (GH hypersecretion - adult)
• gigantism (GH hypersecretion - child)
• Cushings Disease (ACTH)
• Hyposecretion
• pituitary dwarfism

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C. Thyroid Disorders

• Hyposecretion
• congenital hypothyroidism
• myxedema
• Iodine deficiency
• endemic goiter

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D. Parathyroid Disorders

• Hypoparathyroidism
• Hyperparathyroidism

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E. Adrenal Disorders

• Hypersecretion
• Cushings syndrome (cortisol)
• tumor (ACTH)
• Adrenogenital syndrome (angrogens)

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F. Diabetes Mellitus

• Symptoms
• POLYURIA (osmotic diuresis)
• POLYPHAGIA
• POLYDIPSIA
• Hyperglycemia
• Glycosuria
• Ketonuria
• ketoacidosis
• Type I insulin-dependent
• Type II non-insulin-dependent

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VIII. Insight

• Read about the discovery of insulin.