Endocrine system

• Hormones


  Chemical signals in the body that allow communication between different cells and tissues
• Endocrine system


  The system of glands that secrete hormones directly into the bloodstream
• Major endocrine glands


  • Hypothalamus
  • Pineal gland
  • Pituitary gland
  • Thyroid
  • Parathyroid
  • Thymus
  • Adrenal glands
  • Pancreas
  • Ovaries
  • Testes
• Endocrine glands


  • Release hormones directly into the bloodstream (no ducts)
  • Some glands have both endocrine and exocrine functions
• Classes of hormones


  • Amino acid-derived
  • Polypeptide
  • Lipid-derived (steroids)
• Hormone function


  Hormones bind to specific target cells and elicit a response (e.g. increased mitosis, enzyme activation)
• Hypothalamus-pituitary complex


  1. Hypothalamus makes hormones

  2. Posterior pituitary stores and secretes hormones

  3. Anterior pituitary makes its own hormones
• Posterior pituitary hormones


  • Oxytocin
  • Antidiuretic hormone (ADH)
• Anterior pituitary hormones


  • Growth hormone (GH)
  • Prolactin (PRL)
  • Thyroid-stimulating hormone (TSH)
  • Follicle stimulating hormone (FSH)
  • Luteinizing hormone (LH)
  • Adrenocorticotropic hormone (ACTH)
• Pineal gland


  Secretes melatonin, regulates circadian rhythm
• Thyroid gland


  • Secretes T4 (thyroxine) and T3 (triiodothyronine), involved in metabolic processes
  • Also secretes calcitonin, lowers blood calcium
• Parathyroid glands


  Secrete parathyroid hormone (PTH), raises blood calcium levels
• Thymus


  Secretes thymosin, stimulates T cell development
• Adrenal gland parts


  • Adrenal medulla
  • Adrenal cortex
• Adrenal medulla


  Secretes epinephrine and norepinephrine, involved in fight-or-flight response
• Adrenal cortex


  • Secretes glucocorticoids (e.g. cortisol), involved in stress and inflammation
  • Secretes mineralocorticoids (e.g. aldosterone), regulates sodium and potassium
• Pancreas


  • Secretes insulin, allows cells to take up glucose
  • Secretes glucagon, raises blood glucose levels
• Ovaries


  • Secrete estrogen, promotes female sexual characteristics
  • Secrete progesterone, maintains uterine lining
• Testes


  Secrete androgens (e.g. testosterone), promote male sexual characteristics and sperm production
• Estrogen, progesterone, and testosterone are present in all individuals, but in different concentrations and with different primary functions
• Endocrine system signaling


  Slower response time and longer distance compared to nervous system signaling
• Endocrinologists are physicians who specialize in endocrine system conditions