L25 - Calcium metabolism and bone physiology (pt 2) Flashcards
(10 cards)
describe the normal process of bone loss with aging (diagram on slides)
- roughly ages 15-45 are when you have peak bone mass and peak sex steroids
- get a spike of sex steroids after you are born
- get increase in sex steroids throughout puberty and this stays high
- sex steroid level decreases (rapidly for women then levels out after menopause) once you reach around the age of 50
- get decreasing bone mass with age
describe sex steroids promote bone mineral density (diagram on slides)
testsosterone and estrogen are in both females and males, they just have higher levels in specific sexes
- osteoblatsts: testosterone and estrogen stimulate osteoblasts, increasnig bone mineralisation
- osteoclasts: testosterone and estrogen inhibit osteoclasts, decreasing bone resorption
describe osteoporosis
- abnormal loss of bony tissue resulting in brittle porous bones
- > 50% of women and >25% of men will develop osteoporosis
- often asymptomatic until a (fragility) fracture
- can be diagnosed by DEXA scan but usually by fractures, loss of height, curved spine
- was treated with hormone replacement therapy, now usually treated with excerisise, vitamin D/calcium supplements and/or bisphosphonates
what do bisphosphonates do
inhibit osteoclasts by:
- reducing ruffled border formation (ruffled border to increase surface area for fitting secreting proteins on)
- reducing adhesion to bone surfaces (so whatever is getting secreted will escape, resulting in lower concentration in lacunae and wont break down bone through normal chemical reactions)
- readucing acid secretion
- reducing osteoclast progenitor development and recruitment
- increasing osteoclast apoptosis
but can cause osteonecrosis of the jaw (exposure of the jaw through the gums) after dental surgery
what is rickets
- usually from lack fo vitamin D
- usually diagnosed at 3-8 months
- common symptoms inlude: bowed llegs or knock-knees, swelling of wrists, ankles and knees, pain in spine, pelvis and legs, teeth emerge late, and problems with tooth enamel, skull softening, slow fontanelle closure, breastbone sticks out, delayed motor skills and weakness
- treated by vitamin D supplements
describe osteomalacia (soft bones)
- usually from lack of vitamin D in asults (also celiac idsease, kidney/liver dysfunction, anti epileptics)
- abnormal bone formation, making bones soft (oseoporosis is degeneration of existing bonem making bones brittle)
- common symptoms are pain in the bones and hips, bone fractures, muscle weakness and sometimes difficulty walking
- usually diagnosed by lwo levels of plasma vitamin D, calcium and/or phosphate
- usually treated by vitamin D supplements
what is pagets disease
- disrupted bone recycling so, over time, bones become fragile and misshapen
- first symptom is usually bone pain
- four gene mutilations cause Paget’s disease/related syndromes
- sequestosome 1 (SQSTM1) mutilations cause severe disease
- SQSTM1 is a scaffold protein in the RANK-nuclear factor kB (NFkB) signalling pathway
- other potential triggers are calcium deficiency and repeptitive mechanical loading of the skeleton
- treated with bisphosphonates
PTHstimulates ostoblast cytokine (RANK) secretion, p62 is the product of SQSTM1, then changes the tagging and results in either it going in the bin or leading to increased bone resorption
describe hyperparathyroidism (parathyroid disease)
Primary hyperparathryoidism:
- enlargement of parathyroid gland (eg. benign tumors) causes parathyroid hormoone production, incresing plasma calcium levels
- usually corrected by surgery
secondary hyperparathyroidism:
- occurs when something else causes low plasma calcium levels (eg kindey disease, gut disorders)
- increases PTH secretion to try to maintain plasma calcium levels
often asymptomatic but symptoms can include:
- tiredness and/or weakness
- depression and/or forgetfulness
- osteoporosis
- bone and joint pain
- kindey stones
- excessive thirst and urnation
- abdominal pain, nausea and vomiting
describe calcium in tooth formation and maintenance
enamel, dentine, cementum and alveolar bone all have calcium in them, hence it is important in dental practice
- calcium is vital for proper formation and maintenance of teeth and jaw
- enamel is ~96% mineral (HA)
- dentine is ~70% mineral
- cementum is ~65% mineral
what is the impact of poor calcium homeostasis on oral health
- mineralisation of permanent teeth begins around birth and continues until eruption, when the blood supply is severed
- calcium-deficient diets, or a low calcium to phosphorus ratio, can delay eruption, reduce tooth sie, cause hypomineralisation of enamel, dentine and cementum
- in adults, the major impact of low calcium is on alveolar bone, increasing the risk of tooth loss
