bone health

• what is the function of calcium?

  1.Muscle contraction

  2.Blood clotting

  3.Nerve conduction

  4.Bone mineralization

  5.Hormonal communication
• which three hormones regulate calcium levels?

  1.Parathyroid (PTH) hormone

  2.Calcitriol or vitamin D3

  3.Calcitonin
• which cells in the parathyroid glans secrete PTH?

  in response to what?

  • chief cells synthesis and secrete PTH from the parathyroid gland (4 in the body)
  • chief cells secrete PTH in response to low Ca (para think low)
  • PTH = most important regulator of ECF Ca
• how does parathryroid hormone increase Ca levels in response to low serum Ca? what is the effect of PTH on phosphate levels

  1. bone -> increased bone resorption
  2. intestines -> increase dietary/GIT Ca absorption
  3. kidneys -> increased renal reabsorption of calcium

  PTH decreases phosphate reabsorption
• how does PTH act on osteoblasts to increase osteoclastic activity?

  PTH stimulates osteoclast activity (it doesn’t have PTH-R) so PTH acts on osteoblast which signals to osteoclasts to begin bone resorption via RANKL and M-CSF and  which interact with preosteoclasts to activate osteoclast function

  
• Vitamins D2 and D3 are both inactive until they undergo two .....

  where do they undergo these?

  Vitamins D2 and D3 are both inactive until they undergo two hydroxylations

  1.The first hydroxylation occurs in the liver, creating calcidiol

  1.The second hydroxylation occurs in the kidneys and forms calcitriol, the biologically active form of vitamin D
• where is calcitonin secreted from?

  •Is secreted by C cells of the thyroid gland in response to hypercalcemia

  •PTH antagonist
• what does calcitonin do?

  bones -> inhibit osteoclastic activity

  kidney -> increase urinary excretion of phosphate and calcium
• how does ACTIVE vitamin D affect Ca levels?

  • intestine - increases absorption of calcium and phosphorus
  • along with PTH -> reduce Ca lost in the kidneys by urine and stimulate calcium release from bones
• free ionised calcium is tightly regulated by hormones, which of the following is secreted in response to increased serum calcium?

  1. PTH
  2. Vitamin D
  3. Calcitonin

  calcitonin
• outline the negative feedback loop for calcium 


  herer

  
• which hormones apart from the Ca-regulating hormones can have an effect on bone health?

  sex hormones - testosterone and oestrogen

  • growth hormone/ insulin-like growth factor
  • thyroid hormone
  • cortisol
• how does thyroid hormone and growth hormone affect bone health?

  thyroid hormone

  • too much = bone resorption, activates osteoclastic activity

  growth hormone

  • stimulate bone formation and longitudinal growth
• how do glucocorticoids/ cortisol affect bones?

  inhibits bone formation and decreases calcium reabsorption at the intestines
• how do sex hormones affect bone health?

  • maintain bone density by inhibiting osteoclast activity
  • stimulate osteoblasts
  • calcium absorption
  • inhibit bone resorption
• 6 ways to improve bone health?

  • increase calcium intake
  • increase Vit D -> sunshine
  • regular exercise
  • avoid smoking and drinking
  • healthy body weight
  • hormonal health
• what is Vitamin D deficiency called in children vs adults?

  children -> vitamin D

  Adults -> osteomalacia
• what is rickets?


  In children

  • Demineralisation of bone – soft pliable bones
  • Characteristic bow-leg deformity
  • Overgrowth at costochondral junction – rachitic rosary
  • Pigeon chest deformity
  • Frontal bossing
• what is osteomalacia?


  • Softening of bones – frequent fractures
• what is used to dx vitamin D deficiency? (rickets and osteomalacia?)

  • hypocalcemia
  • hypophasphatemia
  • increased alkaline phosphotase
• PTH promotes synthesis of active Vit D3 ..

  here - B

  
• what is FRAX? 


  WHO fracture risk assessment tool -> calculates the probability of fracture over 10 years

  age, sex, weight, height, previous fracture, smoking, glucocorticoids, RA?
• what are the two types of hyperparathyroidism and how are they treated?


  here

  
• what is the neumonic to remember the symptoms of primary hyperparathyroidism?

  stones (renal stones), bones (bone pain), moans (abdominal pain and constipation) and groans (psychiatric – lethargy, depression)”.
• what is Renal Osteodystrophy/CKD Mineral Bone Disorder?


  •broad term for biochemical abnormalities and skeletal manifestations in chronic kidney disease or end-stage renal disease

  •GFR below 60 mL/min
• at what GFR is it considered kidney failure?

  Below 15 GFR is failure
• what are the symptoms for renal osteodystrophy/ CKD Mineral Bone Disorder?

  •Bone pain and fractures

  •Joint pain

  •Bone deformation

  •Slow bone growth

  •Low bone mineral content

  •Some people with early forms of the disease may not have any symptoms
• what are two key concerns with renal osetodystrophy/ CKD Mineral Bone Disorder

  1. failure to synthesise Active Vit D3 -> decreased calcium reabsorption -> decreased bone mineralisation
  2. failure to remove phosphate ions -> hypersphosphatemia -> PO4 bind to serum Ca -> decrease availability of ionised free Ca -> increased PTH
• how does FGF23 production in CKD cause secondary parahyperthyroidism?

  FGF23 produced in bone by osteoblasts and osteocytes under physiological conditions

  •Increase urinary phosphate excretion

  •Involved in vit D metabolism and regulation

  In chronic kidney disease, as a compensatory mechanism, FGF23 levels rise 1000-fold to maintain a neutral phosphate distribution. This compensatory increase in FGF23 promotes the suppression of 1-25-dihydroxyvitamin D production leads to reduction of intestinal calcium absorption increase of PTH level and ultimately develop secondary hyperparathyroidism.
• what are three key things in CKD that cause secondary hyperparathyroidism ?

  • decerased Vit D synthesis
  • hyperphophatemia
  • increased FGF23 production
• what are common causes of osteoporosis?

  •Hormonal related/Postmenoupausal

  •Long use of steroid

  •Malabsorption disease

  •Drug related

  •Low BMI
• what are common symptoms of osteoporosis?

  •Osteoporosis literally means Porous bone (Full of holes)

  •bones are fragile and more likely to break easily

  •Increase bone fragility and susceptibility to fracture

  symptoms:

  • Osteoporosis is painless unless a fracture occurs

  • Significant height loss and curvature of the spine may indicate compression fractures have occurred in your spine
• answer.....


  the answer is A