CC2 LEC -- INTRO TO ENDOCRINOLOGY

• Endocrinology


  Study of the processes 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
  • Major/Dedicated endocrine glands in humans: Hypothalamus, Pituitary gland, Pineal gland, Thyroid gland, Parathyroid gland, Adrenal gland, Islet of langerhans in pancreas, Endocrine pancreas, Ovaries, Testes
• Hormones

  • Chemical substances that act as messenger molecules in the body
  • Hormones could bind to a specific receptor of the target cell
  • Influence biochemical changes in the cell
  • Each hormone is produced by a specific endocrine gland
  • Chemical signals produced by specialized cells secreted into the bloodstream and carried to a target site of action as free hormone or bound to transport protein
  • They play an important role in the growth and development of an organism
  • They are regulated by the metabolic activity either positive or negative feedback mechanism
• Hormone secretion can be stimulated and inhibited by

  • Other hormones: Stimulating hormones
  • Plasma concentrations of ions or nutrient as well as binding Globulins
  • Neurons and mental activity
  • Environmental changes, e.g. Temperature, Light Exposure
• Summary of typical hormone roles

  • Stress response: ex: cortisol, epinephrine
  • Maintenance of Homeostasis: ex: insulin, glucagon, cortisol
  • Regulation of episodic or cyclic events: ex: estrogen, insulin, oxytocin
  • Growth/overall regulation: ex: growth factors, tropic hormones
• Autocrine


  Hormone secreted by a cell and acts on that cell
• Paracrine


  Hormones secreted by a cell and acts on nearby cells
• Endocrine

  Endocrine hormones are released by glands or specialized cells into the circulating blood and influence the function of cells at another location in the body
• Neuroendocrine


  Hormone secreted by nerve cell (the endocrine cell is a neuron) into blood and acts on distant target cells
• Juxtacrine


  Secreted hormones by endocrine cells are released and remain in the plasma membrane of the cell it is secreted
• Exocrine


  Hormones secreted by the endocrine cells are released into the lumen of the gut, from there hormones could affect the function of the gut/GIT
• Neurocrine


  Hormones secreted by the neurons are released into the extracellular space where it would bind to the receptor of nearby cells and affect their function
• General actions of hormones

  • Regulatory function
  • Morphogenesis
  • Integrative action
• Classification of hormones according to composition and structure

  • Peptides and Proteins
  • Steroids
  • Amines
• Classification of hormones according to tissue origin


  • Hypothalamus
  • Anterior Pituitary
  • Posterior Pituitary
  • Adrenal Medulla
  • Adrenal Cortex
  • Parathyroid
  • Thyroid
  • Pancreas
  • Ovaries
  • Testes
• Hormonal interaction

  • Synergistic
  • Antagonistic
  • Permissive
  • Potentiation Reaction
  • Stimulatory Reaction
  • Inhibitory Reaction
• Threshold


  Hormone will not have any physiological effect until hormone threshold is reached
• Concentration effect


  Differential physiology depending on concentration of hormone
• Half-life


  The time it takes for the concentration of a hormone to reduce 50% in the circulation
• Receptor Saturation


  Hormone receptors are not a set number. Can down regulate if bombarded with hormones
• Feedback control

  • Negative Feedback Control
  • Positive Feedback Control
• Endocrinology


  Study of the processes involved in the regulation and integration of cells and organs systems by hormones

  
• Endocrinology

  • Focuses on the effects of Endocrine System to a target cell or organs
  • Function of Endocrine System is specific to a particular cell or to a group of cells

  
• Gland


  Organs, or tissues responsible for the secretion of hormones
• Endocrine System


  • Comes from the Greek words 'Endo' (within) and 'Krine' (secrete)
  • Refers to the collection of hormones
  • Group of ductless glands that secretes hormones necessary for normal growth and development, reproduction, and homeostasis (GDRH)
  • Hormones are released into the external environment of the cells
  • Considered to be the regulatory system of the body
  • Metabolic and biochemical changes are controlled by hormones
  • It is regulated by means of control of hormone synthesis rather than by degradation
• Major Endocrine Glands

  • Hypothalamus
  • Pituitary Gland
  • Pineal Gland
  • Thyroid Gland
  • Parathyroid Gland
  • Adrenal Gland
  • Islet of Langerhans in Endocrine Pancreas
  • Ovaries
  • Testes
• Hormones


  • Act as messenger molecules in the body
  • Chemical signals produced by specialized cells (endocrine cells) secreted into the bloodstream
  • Each hormone is produced by a specific endocrine gland
  • They play an important role in the growth and development of an organism
  • They may cause biochemical changes in the cell or tissue
  • They are regulated by the metabolic activity, either by positive or negative feedback mechanism
• Positive Feedback Mechanism


  • An increase in the product also increases the activity of the system and the production rate
  • Reinforcement of the activity
• Negative Feedback Mechanism


  • An increase in the product decreases the activity of the system and the production rate
  • When the product level is attained, the activity of endocrine system gradually subsides
  • This is the more common regulatory system due its homeostatic function
  • Prevents excess amount of products
• Major Function of Feedback Mechanisms

  To maintain the constancy of chemical composition of ECF and ICF (e.g. Electrolytes)
• Hormone secretion can be stimulated and inhibited by

  • Other hormones (Stimulating- or Releasing- Hormones)
  • Plasma concentrations of ions or nutrients, and binding globulins
  • Neurons and Mental Activity
  • Environmental Changes
• Thyroid-stimulating Hormone (TSH)


  Hormone that stimulates the Thyroid Gland to produce more thyroid hormones
• Parathyroid Hormone (PTH)

  • Hypocalcemia - PTH is released
  • Hypercalcemia - PTH is inhibited
• Stress Response

  • Positive Stress (e.g. overjoy) and Negative Stress (e.g. depression)
  • Cortisol and Epinephrine
  • Heart Rate Regulation
  • BP Regulation
  • Inflammation
• Maintenance of Homeostasis

  • Insulin, Glucagon, Cortisol
  • Maintenance of plasma glucose level
  • Insulin is Hypoglycemic
  • Glucagon & Cortisol are Hyperglycemic
  • Brain directly consumes glucose as its source of energy
  • There are other hormones that maintain homeostasis in electrolytes, enzymes, etc.
• Regulation of Episodic or Cyclic Events

  • Estrogen, Insulin, Oxytocin
  • Regulates lactation among lactating mothers
  • Regulates pregnancy
  • Regulates effect of eating
  • Hyperglycemia after eating
• Growth / Overall Regulation

  • Growth Factors, Tropic Hormones
  • Tropic Hormones regulate production of other hormones
• Hormones may have more than one function
• Hormone Therapy


  • Involves patients who had sex change
  • Gynecological hormones can change physical characteristics of the patient (e.g. Androgenic Hormones - Male Characteristics)
• Autocrine


  • Hormone secreted by a cell and acts on that cell
  • Promotes self-regulation of its own function