hormonal control

• Glands

  • Endocrine
  • Exocrine
• Types of hormones

  • Steroid (lipid soluble, cholesterol based)
  • Protein and peptide (water soluble)
  • Small peptide hormones (e.g. ADH, Oxytocin)
  • Protein/polypeptide (e.g. insulin)
  • Glycoprotein (e.g. FSH)
  • Amine (derived from tyrosine and tryptophan, can be water or lipid soluble)(end in -ine, e.g. adrenaline and noradrenaline (catecholamines), thyroxine)
• How hormones control target cells

  • From outside the cell - fast hormones
  • Inside the cell - slow hormones
• What determines if a hormone works from outside or inside the cell

  • Water soluble hormones work from outside the cell
  • Lipid soluble hormones work inside the cell
• How adrenaline uses a second messenger system - cAMP

  1. Receptor unoccupied: Adenylyl cyclase is inactive and GDP is bound to the Gs-protein

  2. Adrenaline binds: Receptor interacts with the β- and γ-subunits of the Gs-protein

  3. Allows dissociation of GDP and the binding of GTP to the α-subunit of Gs-protein

  4. The α-subunit then leaves the β- and γ-units and interacts with the catalytic portion of the adenylyl cyclase and generates cAMP

  5. Guanosine triphosphatase (GTPase) in the α-subunit converts the GTP back to GDP

  6. The α-subunit then returns to its association with the other Gs-subunits
• How oestrogen works inside the cell

  • As oestrogen is a steroid hormone, it can diffuse through the cell membrane
  • what stops it from diffusing through all cell membranes?
  • interacts with intracellular ERα and ERβ receptors
  • Oestrogen binds to ERα receptor ERβ, binds to oestradiol
  • Both then join to form a dimer and ERβ activates ERα
  • The dimer binds to DNA at oestrogen response points in the promoter region and stimulates protein synthesis and cell proliferation
• How tamoxifen can stop breast cancer

  Is a competitive inhibitor of ERα, blocks estrogen binding
• How insulin works

  1. Via the IMGU (Insulin-mediated glucose uptake) cascade Increases:

  • uptake of glucose from skeletal muscle and adipose tissue
  • Suppresses glucose generation by hepatic cells

  2. The insulin receptor is a transmembrane signal protein with 2 alpha and 2 beta subunits joined by disulfide bonds

  3. The Alpha subunit contains the insulin-binding site

  4. The beta subunit has a transmembrane and cytosolic part which is a tyrosine kinase
• ADH - Anti Diuretic Hormone

  AKA Vasopressin
• What does ADH do?
• What produces ADH?
• What causes the release of ADH?
• What type of hormone is ADH?
• Where does ADH act?
• Hypothalamo-Pituitary Axis


  • Where is the hypothalamus?
  • The hypothalamus links the endocrine and nervous systems
  • Releases chemicals which stimulate the pituitary gland to release hormones
  • Synthesises neurohormones into the circulation via the posterior pituitary
  • Synthesises releasing hormones into the hypophyseal portal blood system which regulate hormones released from the anterior pituitary
• Blood supply to anterior pituitary


  • Carries releasing hormones to pituitary
  • No blood supply here - hormones released by neurosecretion
• Female reproductive system hormonal control provides good examples of both negative and positive feedback
• Female reproductive hormones


  • GnRH
  • FSH
  • LH
  • Oestrogen
  • Progesterone
  • Oxytocin
• Female reproductive hormone control

  1. Puberty: Hypothalamus ↑ GnRH release causing release of FSH and LH from anterior pituitary

  2. FSH and LH cause growth of ovarian tissue; ovarian (steroid) hormones are produced (e.g. oestrogen)

  3. Early cycle: oestrogen inhibits LH and FSH release

  4. Then oestrogen exerts causes surge of LH and FSH: triggers ovulation

  5. Ruptured follicle develops into a corpus luteum
• Oxytocin - an example of positive feedback


  1. Uterine contractions: Helps expel baby and placenta during labour

  2. Milk ejection in response to suckling (let-down reflex)
• Hormonal conditions


  • Diabetes mellitus
  • Acromegaly
  • Diabetes insipidus
  • Grave's Disease
  • Cushing's Disease
• What, where, how! (for the hormonal conditions)