Bone diseases


Bony diseases are comes mainly due to disturbance of calcium homoeostasis, several body organs work mutually to maintain calcium homoeostasis of your body. (Calcium homeostasis is the mechanism by which the body maintains adequate calcium levels in order to prevent hypercalcemia( i.e. excess of calcium or hypocalcemia (low calcium level), both of which can have important consequences for health.)


Figure 2: Integration of the skeleton in mineral and energy homeostasis.In mineral homeostasis, a decrease in circulating calcium stimulates the parathyroid gland to release PTH, which then causes an increase in blood calcium levels by stimulating osteoclastic bone resorption, renal calcium reabsorption and renal production of 1,25(OH)2D to increase intestinal calcium absorption. Increased serum phosphate and 1,25(OH)2D stimulate FGF23 production in bone, which subsequently inhibits PTH production from the parathyroid gland, inhibits 1,25(OH)2D production in the kidney (thereby inhibiting intestinal absorption) and promotes renal phosphate excretion. Endocrine regulation of energy homeostasis by the skeleton is comprised of two mini loops: a negative bone–hypothalamic loop and a positive bone–pancreas loop. Leptin inhibits bone formation and the homeostatic function of the skeleton indirectly through the hypothalamus by suppressing SNS tone. However, SNS signalling also increases the production of osteocalcin from bone, which feeds into the positive loop. Osteocalcin acts on pancreatic β-cells to increase insulin production, which feeds positively back to bone, stimulating osteoblasts and driving further production of osteocalcin. Osteocalcin also acts on fat to increase the production of adiponectin, an insulin-sensitizing hormone. Abbreviations: 1,25(OH)2D, active vitamin D; 25(OH)D, 25-hydroxyvitamin D; FGF23, fibroblast growth factor 23; PTH, parathyroid hormone; SNS, sympathetic nervous system.

By this figure you can understand the relationship of bone to kidney, liver, intestine, liver and brain. If any of these organs disturbed physiologically or pathologically, it may affect calcium homoeostasis and produces bone disease.


How calcium homoeostasis affect bones

Bones formation and resorption (disintegration) is a continuous process, it means exact amount of bone form and dissolve continuously and maintains the required level of calcium in blood. This is regulated by


  1. Liver – vitamin D is converted to Calcidiol in liver via chemical reaction.
  2. Kidney – Calcidiol is converted into Calcitriol in kidney via chemical reaction. This Calcitriol regulates the level of calcium and phosphorous in the blood and bones and helps maintain a healthy bones and skeletal system.
  3. Osteoblast cell of bones- it collects calcium from blood and makes bones
  4. Osteoclast cell of bones – it release calcium into blood from bones
  5. Parathyroid gland – it regulate the calcium release from blood to bone
  6. Brain -  it regulate parathyroid gland secretion according to low or high blood calcium level.

Causes of bone disease

  • Infection
  • Genetic
  • Age related

Whatever may be the reason of bone disease either infection, genetic or age related, there is disturbance of regulatory mechanism of calcium homoeostasis

Some common disease and defective mechanism

  1. Osteoarthritis – bone remodeling process (i.e. formation and resorption) disturbs – may be due to age related hormonal changes.
  2. Osteoporosis – bone mineral density reduced and causes frequent fractures – it occurs due to disturbed calcium homoeostatis.
  3. Osteomyellitis – it is an infectious disease cause inflammation of bone or bone marrow
  4. Osteomalacia – caused by defective bone mineralization which causes softening of bones – due to defective calcium homoeostasis or hyperparathyroidism
  5. Osteopenia – bone mineral density reduced which causes frequent fractures – occurs due to disturbed calcium homoeostatis.
  6. Osteochondroma (bone tumour)
  7. Osteitis deformans (paget’s disease)- genetic  disorder – disturbed osteoblast and osteoclast cell activity, which results unhealthy and uneven bone formation.
  8. Osteogenesis imperfecta -  genetic disorder – bone becomes brittle and easily fractured – bone homoeostasis disturbs
  9. Osteochondritis dissecans – genetic disorder – bone disintegrate itself may be due to poor blood supply- bone homoeostatis disturbs
  10. Osteopetrosis – genetic disorder – reduced osteoclastic cell activity which produces excessive dense formation of bone. Bone becomes very hard.
  11. Osteitis fibrosa cystica – genetic disorder – increased osteoclastic activity due to hyperparathyroidism.


What is to be understood?

  • Not every bone disease needs calcium supplementation.
  • If you have low blood calcium level in any disease, you may take calcium supplementation but for limited time period because you have to rectify the default mechanism which reduces blood calcium level and not only to fulfill the calcium requirement of body.
  • Unnecessary calcium may disturbs another body mechanism and produce diseases



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