endocrinology

    Cards (129)

    • Adenohypophysis
      Anterior pituitary
    • Neurohypophysis
      Posterior pituitary
    • Anterior pituitary doesn't synthesise hormones
    • Anterior pituitary
      • Major endocrine gland, produces several hormones
      • Formed by epithelial outgrowth
    • Posterior pituitary
      • Just stores hormones that are produced by hypothalamus
      • Formed by downgrowth of hypothalamus (mouth)
    • Pars intermedia
      • Thin band of tissue
    • how is the anterior pituitary regulated
      Via the hypothalamus via specialised blood vessels
    • Hypothalamus regulates posterior pituitary
      Via specialised neural pathways
    • Hormone
      Chemical messengers that regulate activities in target cells
    • Hormones that act on anterior pituitary
      • Corticotrophin releasing hormone (causes release of ACTH)
      • Thyrotrophin releasing hormone (stimulates release of TSH and prolactin)
      • Growth hormone releasing hormone (causes release of growth hormone)
      • Somatostatin or growth hormone inhibiting hormone (inhibits release of growth hormone)
      • Gonadotrophin releasing hormone (causes release of LH and FSH)
      • Prolactin releasing hormone (causes release of prolactin)
      • Dopamine or prolactin inhibiting hormone (inhibits release of prolactin)
    • Hormones released by anterior pituitary
      • Growth hormone (GH)
      • Thyroid Stimulating hormone (TSH)
      • Adrenocorticotrophic hormone (ACTH)
      • Follicle Stimulating hormone (FSH)
      • Luteinizing hormone (LH)
      • Prolactin
    • Growth hormone (GH)
      Acts on bone and skeletal muscle, regulates growth
    • Thyroid Stimulating hormone (TSH)

      Stimulates thyroid gland to produce T3 and T4
    • Adrenocorticotrophic hormone (ACTH)
      Stimulates adrenal cortex to secrete glucocorticoid hormones (cortisol, corticosterone)
    • Follicle Stimulating hormone (FSH)
      1. Growth and development of ovarian follicle, M: Production of spermatozoa
    • Luteinizing hormone (LH)

      1. Triggers ovulation, formation of corpus luteum, promotes progesterone secretion, M: Production of testosterone by Leydig cells
    • Prolactin
      Stimulates development of mammary glands, milk production
    • Hormones
      Released/stored by posterior pituitary
    • Oxytocin
      • Acts on uterus, mammary glands
      • Causes uterine contractions, milk let-down
    • Antidiuretic hormone (ADH)

      • Acts on kidneys, blood vessels
      • Stimulates vasoconstriction
      • Promotes reabsorption of water in the kidneys
    • Pineal gland

      • Attached by a stalk to the dorsal wall of the third ventricle of the cerebellum
      • Produces melatonin at night
      • Important for sleep
    • Thyroid gland
      • Functions: growth, metabolism, stores iodine
      • Lies on the trachea directly behind and sometimes overlapping the larynx
      • Paired lobes can sometimes be connected by an isthmus
      • Rare in cats and dogs, thin in horses
      • Secretes T3, T4, calcitonin
    • Thyroid follicles
      • Walls made of simple cuboidal epithelium
      • Contain gelatinous material composed of thyroglobulin (protein)
    • Thyroglobulin
      Synthesised and secreted by epithelial cells lining the follicles, precursor to thyroid hormone
    • Parathyroid gland
      • Usually 4, 2 on each side
      • Located close to or embedded within the thyroid gland
      • Pale colour
      • Play an important role in calcium metabolism - absorption from gut, mobilisation of skeleton, excretion in urine
      • Production of parathyroid hormone is mainly regulated by calcium concentration in plasma
    • Adrenal glands
      • Paired
      • Lie against the roof of the abdomen by the thoracolumbar region
      • Retroperitoneal
      • Craniomedially to the kidney
      • Interior divided into inner medulla and outer cortex
      • Medulla darker colour, cortex yellow, striated
    • Medulla
      The cells of the adrenal medulla produce norepinephrine (noradrenaline) and epinephrine (adrenaline)
    • Cortex
      Produces mineralcorticoids, glucocorticoids and sex steroids
    • Pancreas
      Both exocrine and endocrine gland
    • Exocrine pancreas
      1. Secretes gastric juices into the proximal duodenum via ducts
      2. Helps break down proteins, fats, carbs
    • Endocrine pancreas
      Consists of islets which are the source of insulin, glucagon, gastrin
    • Steroids (administered orally)
      • Exogenous
      • Reduces demand for endogenous production
      • Leads to adrenal atrophy
      • Need to stop taking slowly so adrenal glands can start producing again
      • Otherwise risk of addisonial crisis due to lack of cortisol
    • Steroid types
      • Cortisone
      • Hydrocortisone
      • Prednisolone
      • Methylprednisolone
      • Dexamethasone
      • Betamethasone
      • Budesonide
      • Flumethasone
      • Fluticasone
      • Triamcinolone
    • Regulation of glucocorticoids
      1. Hypothalamus senses stress and releases corticotrophin releasing hormone
      2. Corticotrophin releasing hormone acts on anterior pituitary and causes release of ACTH
      3. ACTH stimulates adrenal cortex and releases glucocorticoids (cortisol)
      4. Cortisol causes negative feedback loop to reduce release of corticotrophin and adrenocorticotropic
    • Glucocorticoid
      Hormone that regulates metabolic functions and related side effects
    • Metabolic functions and related side effects of glucocorticoids
      1. Glucose: ↑gluconeogenesis, ↓ uptake of glucose by the tissues -> hyperglycaemia
      2. Protein: ↓ protein synthesis, ↑ protein catabolism -> muscle atrophy (pot-belly appearance)
      3. Fat: ↑ lipolysis + fatty liver (contributes to pot-belly appearance)
      4. Concentration of urine: antagonist release/effect of ADH
      5. Gastrointestinal system: ↑ absorption, gastric acid secretion, reduced/altered gastric mucous -> risk of GI ulcers
      6. Skin: cutaneous atrophy -> thin skin, hair changes
      7. Calcium: ↑ tissue mobilisation of calcium -> osteoporosis and soft tissue mineralisation
    • Miscellaneous effects of glucocorticoids include polyphagia
    • How glucocorticoids work
      1. Bind to receptor in cell cytoplasm
      2. Move into nucleus
      3. Bind to DNA
      4. Increase/decrease gene transcription
    • Anti-inflammatory actions of glucocorticoids
      • Suppress pro-inflammatory gene-expression
      • Inhibit immune cell activation
      • Dampen signalling pathways
    • Anti-inflammatory effects of glucocorticoids
      1. ↓ capillary blood flow and vasodilation/vasoproliferation
      2. ↓ Platelet aggregation
      3. ↓ fibrin deposition
      4. ↓ collagen formation
      5. ↓ production of pro-inflammatory proteins
      6. ↓ production of anti-inflammatory proteins