Hormones

• Are chemicals produced by cells and carried in the blood to bring about an effect in the body
• Usually produced by endocrine glands and control activities from growth, reproduction, solute concentration of the blood, glucose concentrations and blood temperature
• Nerves communicate along cells via nerve impulses, hormones are the chemical form of communication between tissues and cells and travel in bloodstream
• Hormones move through the bloodstream, reaching all cells
• Each type of hormone is designed to target and affect different target cells (receptor specific) to influence metabolic processes 
• Three types or classes of hormones

  • Peptide and protein hormones
  • Amino acid derived hormones
  • Lipid/steroid hormones
• Peptide and protein hormones

  • Consist of short/long chains of amino acids
  • Synthesised in the RER
  • Require cleavage to activate
  • Stored in vesicles
  • Most are polar (water soluble)
  • Travel in the blood
  • Bind to receptors in the cell membrane activating secondary messengers
• Peptide and protein hormones

  • Insulin
  • Glucagon
  • Antidiuretic hormone (ADH)
• Protein and peptide hormones are often polar (water soluble) and do not travel into the cell
• Their action occurs as a result of binding to target cell membranes that possess complementary receptors to the hormone
• Steroid hormones are non polar (lipid soluble) and bring about their effects by travelling into the cell and binding with internal receptors 
• Hormones influence

  • Activation of Enzymes
  • Regulation of gene expression
  • Modification of cellular transport
  • Alteration of metabolic pathways
  • Impact on cellular signalling
  • Modification of cellular growth and differentiation
• Activation of Enzymes

  Hormones often activate or inhibit specific enzymes that control metabolic pathways
• Insulin activates glucagon


  To lower blood glucose
• Regulation of gene expression

  Hormones can influence the transcription of specific genes, leading to changes in the synthesis of proteins and enzymes involved in metabolism
• Thyroid hormones

  Increase the expression of genes involved in metabolic rate
• Modification of cellular transport

  Hormones can alter the activity of transport proteins, affecting the movement of substances such as glucose, amino acids and ions into and out of cells
• Alteration of metabolic pathways

  Hormones can influence the direction and rate of metabolic pathways by affecting key regulatory steps
• Impact on cellular signalling


  Hormones can affect intracellular signalling pathways that regulate various metabolic processes
• Modification of cellular growth and differentiation

  Hormones can influence cell growth, differentiation and proliferation, which can indirectly affect metabolism
• Amino acid derived hormones

  • Derived from amino acids tyrosine and tryptophan
  • Synthesised from one amino acid
  • Stored before release
  • Some are lipid soluble
  • Some are water soluble
  • Some act on cell membrane receptors
  • Others bind to receptors inside the cell
• Amino acid derived hormones

  • T3
  • T4 (thyroxine)
  • Adrenaline
  • Melatonin
• Lipid/steroid hormones

  • Lipid based hormones
  • Derived from cholesterol
  • Usually insoluble in water
  • Travel through the blood bound to proteins
  • Synthesised from cholesterol
  • Released into the bloodstream immediately
  • Non polar (lipid soluble)
  • Bind to intracellular receptors
• Lipid/steroid hormones

  • Progesterone
  • Oestrogen
  • Testosterone