ENDROCRINOLOGY

• Endocrinology


  The study of the process involved in the regulation and integration of cells and organ systems by hormones
• Endocrine System


  • Group of ductless glands that secrete hormones necessary for normal growth and development, reproduction and homeostasis
  • Ductless - secrete and release substances directly into the blood or external environment
  • Regulates the metabolic activity of many cells and organs through positive or negative feedback mechanism
• Major endocrine glands


  • Hypothalamus
  • Pituitary Gland
  • Pineal Gland
  • Thyroid Gland
  • Parathyroid Gland
  • Adrenal Gland
  • Islet of Langerhans in the Pancreas
  • Testes/Testis
  • Ovary
• Endocrine System


  • A network of ductless glands of internal secretions
  • Greek: Endo - within; Crine - secrete = Release or Secretion within
  • The regulatory system of the body
  • Formation of hormone is what controls the overall function of ES
  • Collection of hormones
• Hormones


  • Chemical substances that act as messenger molecules in the body
  • Can be a protein, lipid/fat, or amino acid type
  • Carry messages and affect the metabolic activity of the target cell or tissue
  • Main functioning component
  • Chemical signals produced by specialized cells secreted into the blood stream and carried to target site bloodstream and carried to a target site of action as free hormone or bound to transport protein.
• Each hormone is produced by a specific endocrine gland
• Hormones


  Chemical signals produced by specialized cells secreted into the blood stream and carried to a target site of action as free hormone or bound to transport protein
• Positive feedback


  Increased in the product also increases the activity of the system and the production rate
• Negative feedback


  Increased in the product decreases the activity of the system and the production rate
• Hormone secretion can be stimulated and inhibited by

  • other hormones
  • plasma concentrations of ions and nutrients, as well as binding globulins
  • neurons and mental activity
  • environmental changes
• Typical hormone roles


  • Stress response (e.g. cortisol, epinephrine)
  • Maintenance of homeostasis (e.g. insulin, glucagon, cortisol)
  • Regulation of episodic or cyclic events (e.g. estrogen, insulin, oxytocin)
  • Growth/overall regulation (e.g. growth factors, trophic hormones)
  • Hormes may have more than one function (e.g. cortisol, insulin)
• Types of hormone actions

  • Autocrine
  • Paracrine
  • Endocrine
  • Neuroendocrine
  • Juxtacrine
  • Exocrine
  • Neurocrine
• Actions of hormones


  • Regulatory function
  • Morphogenesis
  • Integrative action
• Peptide and protein hormones

  • Synthesized in the Rough Endoplasmic Reticulum
  • Secretory peptides synthesized in Polyribosomes as preprohormones
• Action of hormones


  • Regulatory function
  • Morphogenesis
  • Integrative action
• REGULATORY FUNCTION

  • Maintain constancy of the chemical composition of the ECF and ICF
  • Regulate electrolytes and nutrients
  • Maintain concentration in and out of the cell for homeostasis
• INTEGRATIVE ACTION

  • Have specific functions but multiple hormones from different glands may regulate a single function
  • Function individually or together to execute a particular function
• Classification of hormones according to composition and structure

  • Peptides and proteins
  • Steroids
  • Amines
• Peptide and protein hormones

  • Synthesized in the Rough Endoplasmic Reticulum
  • Synthesized as larger complex precursors (prehormone or preprohormone)
  • Stored within cells in secretory granules and cleaved as needed
  • Cannot cross cell membrane, only act on cell surface
  • receptor site: cell membrane
  • hydrophilic
  • not bound to carrier protein
• Steroid hormones


  • Synthesized in the Smooth Endoplasmic Reticulum
  • Cholesterol as precursor
  • No storage form
  • Water-insoluble, bound to protein carrier
  • Act by modulating gene expression
  • Receptor site: nucleus
  • Slower onset of action but longer lasting
  • Made by adrenal cortex, ovaries, testes, placenta
  • steroid from these lands fall into 5 categories: progestins, mineralocorticoids, glucocorticoids, androgens, estrogens
  • EXAMPLE: aldosterone, cortisol, gynecological hormone (estradiol, estrone, progesterone), and androgenic hormone (testosterone)
• Amine hormones


  • Derived from amino acids
  • Intermediary between steroid and protein hormones
  • Function similar to steroid or peptide hormones
  • storage form: granules, vesicles
  • forms in: RER
  • Synthesized in the cytoplasm of endocrine cells
  • Mostly derived/originated from tyrosine and some from tryptophan
• Amine hormones


  • Epinephrine
  • Norepinephrine
  • T3
  • T4
  • Serotonin
• Classification of hormones by tissue origin

  • Hypothalamus: TRH, GnRH, CRF
  • Anterior pituitary gland: TSH, ACTH, FSH, LH, Prolactin, Growth Hormone
  • Posterior pituitary gland: Vasopressin, Oxytocin
  • Adrenal medulla: Epinephrine, Norepinephrine
  • Adrenal cortex: Cortisol, Aldosterone
  • Parathyroid: PTH
  • Thyroid: T3, T4, Calcitonin
  • Pancreas: Insulin, Glucagon
  • Ovaries: Estrogen
  • Testes: Testosterone and other androgens
• Hormonal interactions


  • Synergistic
  • Antagonistic
  • Permissive
  • Potentiation
  • Stimulatory
  • Inhibitory
• Hormone concentration


  • Threshold - minimum concentration required for physiological effect
  • Concentration effect - differential effects depending on hormone concentration
  • Half-life - time for concentration to reduce by 50%
  • Receptor saturation - receptors can be downregulated if overwhelmed by hormones; hormone receptors are not ser number
  • Positive feedback - increased product leads to increased production rate; example: labor/birth, lactation
  • Negative feedback - increased product leads to decreased production rate; common homeostatitic mechanism
• MORPHOGENESIS- controlling the growth and development of organism
• STRESS REPONSE

  • cortisol, epinephrine
  • heart rate regulation, BP, inflammation
• MAINTENANCE OF HOMEOSTASIS

  • Insulin – hypoglycemic agent; takes effect when plasma glucose level is high.
  • Glucagon – hyperglycemic agent
  • Cortisol - hyperglycemic agent Maintain more or less constant conditions = homeostasis.
  • These 3 could regulate the blood or plasma glucose level and energy supplies in the body since glucose can also generate energy or ATP
• REGULATION OF EPISODIC OR CYCLIC EVENTS

  • Estrogen
  • Insulin
  • Oxytocin
  • These could control the different cyclic events in the human body.
  • Lactation – among lactating mothers
  • Pregnancy – also an episodic event among women
  • Effects of eating – when we eat we normally become hyperglycemic
• GROWTH/OVERALL REGULATION

  • Growth factors Trophic hormones - Could regulate the production of other hormones
• AUTOCRINE

  • Hormone secreted by a cell and acts on that cell.
  • Secreted by cells into the ECF and affect the function of the same cells that produced them binding to cell surface receptors.
  • The glandular cells secrete this hormone that is when released the target is a specific receptor on that particular cell.
  • Could result to self-regulation of its function.
• PARACRINE

  • Hormones secreted by the cell and acts on nearby cells.
  • Paracrine are secreted by cells into the ECF and affect neighboring cells of different types.
  • Hormones secreted into the EC space can also regulate nearby cells without ever passing through the systemic circulation.
  • Release the hormones to the ECF and will bind to the specific receptor of adjacent cells and affect the function of nearby cells.
  • The nearby cells will have different biochemical activities
• ENDOCRINE

  • Hormones are released by glands or specialized cells into the circulating blood/systemic circulation and influence the function of cells at another location in the body.
  • Binding of hormone and receptor could elicit a biochemical action.
• NEUROENDOCRINE

  • Hormones secreted by the nerve cell [endocrine cell is a neuron] into blood and acts on distant target cells.
• EXOCRINE

  • Hormones are released into the lumen of the GUT of the GIT.
  • These could bind to the receptors and affect the function of the tissues and the cells. Could affect the function of the GUT of the GIT.
  • Exocrine kasi from the circulation, nirelease sya into the GIT or outside the circulation na.
• NEUROCRINE

  • Hormones are released into the EC space and binds to the receptor of the nearby cell and affects its function.
  • Neurocrine vs Neuroendocrine = both secreted by the neurons
  • Diff = location of the target cell
  • Neurocrine – nearby, neighboring, adjacent
  • Neuroendocrine – distant
• GLYCOPROTEINS------POLYPEPTIDES

  • FSH----- ACTH [Adrenocorticotropic Hormone]
  • hCG---- ADH/Arginine Vasopressin
  • TSH---- GH
  • (11) Erythropoietin----- Angiotensin, Calcitonin, Cholecystokinin, Gastrin , Glucagon, Insulin, MSH [Melanocyte Stimulating Hormone], Oxytocin, PTH, Prolactin, Somatostatin
• SYNERGISTIC

  • 2 or more hormones are additive/ complementary in effect.
  • Example: FSH and LH
  • Activity will have similar effect to the cell
• Antagonistic


  – the function of 1 hormone offsets another hormone.

  o Action of the 2 contradicts each other.

  o Example: regulation of plasma glucose involves insulin

  [for increased blood glucose] and glucagon [for

  decreased blod glucose]
• Potentiation Reaction

  • the presence of 1 hormone increase the action of another hormone.
  • Example: ACTH and Androgen
  • If ACTH is present = activity of Andrigen is increased