LEC 30: PITUITARY, THYROID, PARATHYROID GLANDS

• Pituitary gland (hypophysis)


  Located below hypothalamus, connected to brain by infundibulum
• Pituitary gland

  • Two lobes: Anterior Pituitary (glandular epithelial tissue), Posterior Pituitary (neural tissue)
• Anterior Pituitary Hormones


  • Gonadotropins (FSH, LH)
  • Prolactin
• Gonadotropins


  Regulate the function of gonads (ovaries & testes)
• FSH


  Stimulates production of gametes
• LH


  Promotes tissues in gonads to produce gonadal hormones (testosterone & estrogen)
• Prolactin


  Stimulates milk production
• Posterior Pituitary Hormones


  • Oxytocin
  • ADH
• Oxytocin


  Promotes uterine contractions, sexual & affectionate behaviour (bonding hormone), promotes nurturing & trust
• ADH


  Targets kidney tubules to reabsorb more water
• Triggers for ADH production

  Pain or low BP
• Inhibitor of ADH production

  Alcohol
• Production of ADH can be affected by physical trauma
• Lack of ADH production results in diabetes insipidus
• Thyroid gland


  • Follicular cells produce thyroglobulin, Parafollicular cells produce calcitonin
• Thyroid hormones

  • Thyroxine (T4)
  • Triiodothyronine (T3)
• Thyroid hormones


  Act on all body cells to increase basal metabolic rate (energy expended while at rest) & body heat, affect skeletal and nervous system development
• Steps to synthesize thyroid hormone

  1. Thyroglobulin is synthesized and secreted to the follicle lumen

  2. Iodide is trapped and oxidizes to iodine

  3. Iodine attaches to tyrosine portion of thyroglobulin

  4. Iodinated tyrosines linked = forms T3 & T4

  5. Thyroglobulin colloid transported into follicular cells so thyroglobulin can be removed, allowing hormone to diffuse into the bloodstream
• Myxedema (hypothyroidism)


  Hyposecretion of thyroid hormone in adults, results in low metabolic rate, feeling chilled, edema & lethargy
• Goiter


  Hyposecretion due to lack of iodine, triggers thyroid to swell as it synthesizes more unusable thyroglobulin
• Calcitonin


  Secreted by parafollicular cells of thyroid, antagonist to parathyroid hormone, inhibits osteoclast activity & stimulates incorporation of Ca2+ into bone matrix
• Parathyroid hormone


  Released in response to low Ca2+ levels, encourages osteoclasts to break down bone to raise blood Ca2+
• Hyperparathyroidism


  Too much parathyroid hormone, leaches calcium from bone causing bones to soften & deform
• Hypoparathyroidism


  Can cause hypocalcemia (not enough calcium for muscle contractions), untreated can stop breathing and heart contractions
• how many hormones are produced by the anterior pituitary gland?

  6
• how many hormones secreted by posterior pituitary gland?

  2