Endocrine Anatomy

Aka: Endocrine Anatomy, Autocrine, Paracrine, Hormone

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II. Definitions

  1. Cytokine
    1. See Cytokine
    2. Short-range, cell-released molecules that influence the same cell (Autocrine) or nearby cells (Paracrine)
  2. Autocrine Communication
    1. Cytokines that influence the same cell that released the molecule
  3. Paracrine Communication
    1. Cytokines that diffuse to influence nearby cells
  4. Endocrine Glands
    1. Glands that secrete hormonal agents that act systemically
    2. Contrast with exocrine glands (e.g. Salivary Glands) that secrete molecules locally into ducts
  5. Hormones
    1. Molecules secreted by endocrine organs, and carried by the vascular system to influence cells at distant sites
    2. Hormones may be Proteins (e.g. TSH), Amino Acid derivatives (e.g. Thyroxine) or steroid rings (e.g. Progesterone)
    3. Hormones act at specific receptors on cell membranes, in the cytoplasm or within the cell nucleus
    4. Each Hormone may act at multiple different receptors with different effects (e.g. Epinephrine at a1, a2, b1, b2; Histamine at h1-4)
    5. Hormones may modify enzyme synthesis or activity, or affect other cellular function (e.g. cell membrane permeability)

III. Physiology: Hormonal Activity

  1. Polypeptides (e.g. Epinephrine)
    1. Bind cell surface receptors
    2. Receptor binding triggers G Protein (intermediate molecule) release
    3. G Proteins stimulate secondary messenger release (e.g. cAMP, cGMP, Inositol triphosphate, diglyceride, Calcium) within the cell
  2. Steroid Hormones (e.g. Progesterone)
    1. See Steroid Hormone Pathway
    2. Bind cytoplasmic receptors to form molecule complex
    3. Complex enters nucleus to influence Protein transcription
  3. Amino Acid Derivatives (e.g. Thyroxine)
    1. Thyroxine enters cells and acts directly within nucleus to influence Protein transcription

IV. Preparations: Hypothalamus and Pituitary Hormones

  1. Hypothalamus
    1. Corticotropin Releasing Hormone (CRH, CRF)
      1. Stimulates anterior pituitary release of Adrenocorticotropic Hormone (ACTH)
    2. Gonadotropin Releasing Hormone (GnRH, LHRH)
      1. Stimulates anterior pituitary release of Follicle Stimulating Hormone (FSH)
      2. Stimulates anterior pituitary release of Luteinizing Hormone (LH)
    3. Growth Hormone Releasing Hormone (GHRH)
      1. Stimulates anterior pituitary release of Growth Hormone
    4. Thyrotropin Releasing Hormone (TRH, TRF)
      1. Stimulates anterior pituitary release of Thyroid Stimulating Hormone (TSH)
      2. Stimulates anterior pituitary release of Prolactin
    5. Somatostatin
      1. Inhibits anterior pituitary release of Growth Hormone
      2. Inhibits anterior pituitary release of Thyroid Stimulating Hormone (TSH)
    6. Neurotransmitters
      1. Dopamine released from Hypothalamus inhibits anterior pituitary release of Prolactin
  2. Posterior Pituitary Gland (Hormones produced in the Hypothalamus, released from pituitary)
    1. Oxytocin
      1. Stimulates uterine contractions
      2. Stimulates milk let-down in Lactation
    2. Antidiuretic Hormone (ADH, Vasopressin)
      1. Increases renal water reaborption
  3. MIddle Pituitary Lobe
    1. Melanocyte Stimulating Hormone
      1. Peptide Hormone promoting Melanin pigment within the skin
  4. Anterior Pituitary Gland
    1. Prolactin
      1. Protein synthesized and secreted by Lactotrophs (acidophil cells) in the anterior Pituitary Gland
      2. Prolactin stimulates milk secretion into the Breast alveoli in pregnancy and Lactation
      3. Oxytocin stimulates myoepithelial cells to contract, expressing Breast Milk from the nipple
      4. Stimulated by Estrogen, vasoactive intestinal polypeptide (VIP), Thyroid Releasing Hormone (TRH)
      5. Inhibition by hypothalamic Dopamine (Prolactin Inhibiting Factor or PIF)
    2. Human Growth Hormone
      1. Polypeptide produced in the acidophil cells of the anterior Pituitary Gland
      2. Triggered by Hypoglycemia (or low Amino Acids) via hypothalamic release of GHRH
      3. Promotes bone and cartilage growth, Protein synthesis, glycogen storage, Fatty Acid increase
    3. Adrenocorticotropic Hormone (ACTH)
      1. Polypeptide synthesized and secreted by Basophil cells in the anterior Pituitary Gland
      2. Stimulation (releasing factors) include Corticotropin Releasing Hormone (CRH) and stress
      3. Inhibition by negative feedback loops (Cortisol inhibits CRH and ACTH release)
      4. ACTH stimulates the Adrenal Cortex to release Cortisol (and to a lesser extent Aldosterone and androgens)
    4. Thyroid Stimulating Hormone (TSH)
      1. See Thyroid Physiology
      2. Thyroid Stimulating Hormone (TSH) is a Glycoprotein synthesized in the Basophil cells of the anterior Pituitary Gland
      3. Stimulated by Thyroid Releasing Hormone (TRH)
      4. Inhibited by negative feedback from Thyroid Hormones (T4, T3)
      5. Thyroid Stimulating Hormone (TSH) promotes all aspects of Thyroid Hormone production
        1. Increases Iodide uptake and incorporation of Iodine into Thyroglobulin
        2. Increases lysis into active Thyroid Hormones T4 and T3
    5. Follicle Stimulating Hormone (FSH)
      1. FSH is a glyoprotein secreted by Basophil cells in the anterior Pituitary Gland
      2. Stimulation (releasing factors) is by Hypothalamic Gonadotrophic Releasing Hormone (GnRH)
      3. Inhibited via negative feedback loop by Testosterone, Estrogens, Progesterone and inhibin
      4. FSH stimulates ovarian follicle growth (which secretes Estradiol) in women
      5. FSH stimulates spermatogenesis and sperm maturation within Sertoli Cells in men
    6. Luteinizing Hormone (LH)
      1. LH is a Glycoprotein secreted by Basophil cells in the anterior Pituitary Gland
      2. Stimulation is by Hypothalamic Gonadotrophic Releasing Hormone (GnRH)
      3. Inhibited via negative feedback loop by Testosterone, Estrogens, Progesterone and inhibin
      4. LH stimulates ovarian follicles to ovulate and mature into a corpus luteum (produces Estrogen, Progesterone)
      5. LH stimulates Leydig Cells within Testes to produce Testosterone

V. Preparations: Adrenal Hormones

  1. Physiology Images
    1. AdrenalFunction.png
    2. CholesterolDerivedSteroidHormones.png
  2. Adrenal Medulla (sympathetic agent synthesis)
    1. See Sympathetic Nervous System
    2. See Alpha Adrenergic Receptor
    3. See Beta Adrenergic Receptor
    4. Inner structure of the Adrenal Gland
    5. Functions as a sympathetic Ganglion that releases Sympathomimetics in response to stressors
    6. Epinephrine
      1. Primary Adrenal Medulla released Catecholamine (more than Norepinephrine)
      2. Alpha Adrenergic Agonist Effects
        1. Vasoconstriction (increased Systemic Vascular Resistance and Blood Pressure)
        2. Increases Vital Organ Perfusion (myocardial perfusion, cerebral perfusion)
        3. Decreases Non-Vital Organ Perfusion (splanchnic, intestinal, renal and skin perfusion)
      3. Beta 1 Adrenergic Agonist Effects (at physiologic doses)
        1. Increases myocardial contractility
        2. Increases Heart Rate
      4. Beta 2 Adrenergic Agonist Effects
        1. Relaxes Bronchial Smooth Muscle (bronchodilation)
        2. Stimulates Gluconeogenesis, lipolysis and glycogen breakdown
    7. Norepinephrine
      1. Neurotransmitter for all other postganglionic sympathetic Neurons
      2. Potent Alpha 1 Adrenergic ReceptorAgonist Effects
        1. Potent arterial and venous Vasoconstriction
      3. Beta 1 Adrenergic ReceptorAgonist Effects
        1. Similar potency to Epinephrine
        2. Increases myocardial contractility
      4. No Beta 2 Adrenergic Receptor Activity
  3. Adrenal Cortex (steroid Hormone synthesis from Cholesterol)
    1. See Adrenal Gland Physiology
    2. See Steroid Hormone Pathway
    3. Outer structure of the Adrenal Gland
    4. Mineralcorticoids (esp. Aldosterone)
      1. See Sodium and Water Homeostasis
      2. See Renin-Angiotensin System
      3. Increases Sodium retention and Potassium excretion
      4. Increases water reabsorption from Kidney
    5. Glucocorticoids (esp. Cortisol)
      1. Mobilizes available energy sources (Glucose, fats, Amino Acids)
        1. Increases Serum Glucose by stimulating liver Gluconeogenesis and glycogenolysis
        2. Increases serum Fatty Acids by promoting lipolysis of adipose Triglyceride stores
        3. Increases blood Amino Acids by breaking down Proteins (outside liver)
          1. Within liver, Cortisol induces Protein synthesis
      2. Antiinflammatory activity
        1. Inhibit Histamine release
        2. Inhibit Lymphocyte production
        3. Stabilize MacrophageLysosomes
      3. Increases gastric acid production
    6. Androgens
      1. Dehydroepiandrosterone (DHEA)
      2. Androstenedione
      3. Testosterone

VI. Preparations: Miscellaneous Hormones

  1. Sex Hormones
    1. CholesterolDerivedSteroidHormones.png
    2. See Menstrual Cycle
    3. Human Gonadotrophin (HCG)
    4. Estrogen
    5. Progesterone
    6. Testosterone
  2. Glucose Metabolism
    1. Insulin
    2. Glucagon
  3. Gastrointestinal Hormones
    1. Gastrin
    2. Secretin
    3. Leptin
    4. Cholecystokinin
  4. Thyroid Hormones
    1. Thyroxine (T4)
    2. Triiodothyronine (T3)
  5. Calcium Metabolism
    1. Parathyroid Hormone
    2. Calcitonin
  6. Cardiac Hormones
    1. Atrial Natriuretic Factor or Peptide (ANF, ANP)

VII. Anatomy: Endocrine Components

  1. Adrenal Anatomy
  2. Thyroid Anatomy
  3. Parathyroid Anatomy
  4. Pituitary Anatomy
  5. Testes Anatomy
  6. Ovary Anatomy

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