Bone Diseases Flashcards
What is it called when one has too much calcium?
hypercalcemia
What are four examples of disorders that cause hypercalcemia?
1) hyperparathyroidism
2) increased bone resorption freeing calcium
3) increased gut absorption of calcium
4) decreased kidney excretion
What are the symptoms of hypercalcemia?
- anorexia, nausea, vomiting, renal salt and water loss
- extracellular fluid volume contraction
- decrease in calcium excretion (causes more hypercalcemia)
What is the cause and effect of hyperparathyroid disease?
- causes hypercalcemia and other symptoms
- could result from a tumour
What does hyperparathyroid do to calcium levels?
- usually calcium levels suppress parathyroid hormone transcription and secretion
- here parathyroid hormone is out of control and increases serum calcium
What is used to treat hyperparathyroid?
- calcitonin
- causes rapid decline of serum calcium and phosphorous by acting on bone
- acts faster than parathyroid hormone
What is calcitonin’s main function?
- inhibits osteoclast mediated bone resorption
What are two possible causes of hypocalcemia?
- hypoparathyroid
- corticosteroid medications (ex. prednisone) which decrease calcium absorption
What is a common symptom of hypocalcemia?
- muscle spasm
What are some symptoms of hypercalcemia (hyperparathyroidism)?
- muscle twitching, anxiety, depression, confusion, personality changes
What is rickets?
- occurs in children
- bones growing, not fused
- lack of vitamin D causes decrease in calcium and phosphate
- results in secondary hyperthyroidism and increased bone resorption
What are some visual characteristics of a child with rickets?
- bow legs and humpback
What program was implemented in Canada and US to decrease rickets?
- milk fortification
What is osteomalacia?
- occurs in adults
- fused bone
- mineralization of newly formed bone matrix is defective
What is osteomalacia caused by?
- lack of vitamin D, low calcium, or low phosphate
There are many factors of rickets and osteomalacia including?
cytokines
What is type I vitamin D deficiency?
- lack of vitamin D
- due to environment or genetic defect (defective enzyme)
What is type II vitamin D deficiency?
- normal vitamin D levels but insensitive due to defect in receptor called alopecia
What do laboratory, animal and epidemiologic evidence suggest about vitamin D and cancer?
- vitamin D may be protective against some cancers
What happens if you have excessive sun exposure?
- does not result in vitamin D toxicity because the sustained heat on the skin photodegrades and nonactive products form
What happens if you have excessive intake of vitamin D?
- long-term intake above the upper limit
- increase risk of vitamin D toxicity
What is Lytic Paget’s disease?
- aka Osteitis Deformans
- rapid bone loss because of accelerated bone turnover (rate of bone resorption too high)
What is Lytic Paget’s disease associated with?
- osteoarthritis
What is used to treat Lytic Paget’s Disease?
calcitonin
What is the pathogenesis of Renal Secondary Hyperparathyroidism?
- kidney deterioration causes vit D problem
- phosphate retention downregulates vitamin D and can’t produce as much in kidney
- decreases calcium and increase parathyroid hormone
What is vitamin D normally upregulated by?
- low phosphorous, low calcium, high parathyroid hormone, low vitamin D
How does parathyroid hormone get out of control due to kidney damage?
- usually vitamin D and calcium inhibit parathyroid hormone synthesis
- in damaged kidney, high parathyroid hormone not able to activate enough vitamin D and high phosphate downregulates vitamin D as well
What is osteroporosis?
- decrease of bone mineral density
What can be used to treat osteoporosis?
- calcitonin or hormone therapy
- healthy diet and exercise
What causes osteoporosis?
- bone mineral density decreases with age
- low estrogen and high glucocorticoids
- long-term vitamin D insufficiency because of decreased calcium absorption
What is bone health affected by?
- bone mass, bone architecture and body mechanics
- nutrition and hormones affect these
What principle nutrients affect bone health?
- calcium, protein, potassium, magnesium, zinc, vitamins
Which hormones affect the bones?
- vitamin D and parathyroid hormone
- also estrogen, testosterone, glucocorticoids and others
What does estrogen do in relation to bone health?
- acts on osteoclasts and osteoblasts to inhibit bone breakdown
- stimulates bone formation
What does testosterone do in relation to bone health?
- stimulates muscle growth (puts stress on bone and increases formation)
- source of estrogen (converted in fat cells)
What contributes to bone loss?
- glucocorticoid excess
What target cells have receptors for calcitriol (vitamin D)?
- intestine, kidney, bone, immune cells, breast, testicular tissue
What cells have receptors for parathyroid hormone?
- kidney cells (uptake calcium into blood)
- bone osteoblasts and pre-osteoclasts that stimulate bone breakdown (release calcium into blood)
- no receptors in intestine but still has effect on vitamin D there
What cells have receptors for calcitonin?
- osteoclasts
