Week 4: Parathyroid Hormones

parathyroid hormone regulates

calcium homeostasis

calcium is crucial for what 3 things

synaptic transmission, muscle contraction, bone mineralization

high serum calcium suppresses

PTH secretion

low serum calcium stimulates

PTH release

3 effects of parathyroid hormone

directly on kidney to increase calcium reabsorption, PTH directly increases bone mass, PTH indirectly improves GI tract calcium absorption

pth on bone formation

normal release enhances bone formation and stimulates osteoblast activity and anabolic (build up)

A prolonged increase of PTH increases

blood calcium levels which causes breakdown and hypercalcemia

vitamin D action on bone

enhances formation by increasing supply of calcium and phosphate

vit d suppresses synthesis and release of

pth from parathyroid to promote bone mineralization by limiting catabolic effects of pth

if dietary levels of calcium are low or gi absorption is low, active form of vitamin D will...

increase bone resorption and decrease bone mineralization

calcitonin

produced by thyroid has opposite effects of PTH but is not as dominant

effects of PTH

lower serum calcium by stimulating bone formation and increasing calcium storage in bone, enhance phosphate storage in bone, renal excretion of calcium and phosphate when increased

hormones that enhance bone formation

estrogen, androgen, growth hormone, insulin, thyroid

hormones that enhance resorption

glucocorticoids, certain prostaglandins (why nsaids arent recs post fracture)

drugs used to control bone mineral homeostasis

bisphosphonates, calcitonin, calcium supplements, vit d analogs, estrogens

why use drugs to control bone mineral homeostasis

prevent bone loss and treat establish osteoporosis

bisphosphonates

absorb directly into calcium crystals in bone and reduce bone resorption by inhibiting osteoclast activity

what do bisphosphonates treat

osteoporosis and pagets

adverse effects of bisphosphonates

gi disturbances (take w food and remain upright for 30-60 min)

Selective Estrogen Receptor Modulators (SERMS)

activate certain receptors while blocking others (mixed agonist-antagonist)

what do SERMS activate/block

activates estrogen receptors on bone

blocks estrogen on breast/uterine tissue

adverse effects of SERMS

increase risk of VTE

calcium supplements

reduces bone loss in post menopausal women but doesnt increase density once loss, depends on patient factors

for optimal effect of calcium supplements, combine it with

vitamine D because calcium is not well absorbed in GI system

vitamin D toxicity

early: headache, thist, metallic taste, fatigue

late: hypercalcemia, htn, arrhythmias, renail failure

estrogen

used in post menopausal women or after ovariectomy to increase mineral content in bone and reduce fractures

risk of estrogen

increased risk of CV disease and cancers

parathyroid hormone is used to

stimulate bone formation and increase bone mass via injection

calcitonin used to treat what main disease

osteoporosis

side effects of calcitonin

redness, swelling at injection site, flushing in hands and feet

teriparatide

synthetic form of PTH to increase bone formation and used in very high risk of osteoporotic fractures

cinacalcet (calcimimetic agent)

mimics effect of calcium leading to decrease in PTH release, increase sensitivity of calcium to decrease PTH and serum calcium

who mainly uses calcimimetic agents

those with secondary hyperparathyroidism in those with dialysis or parathyroid tumor

rehab concerns for parathyroid

know side effects on heart, have interventions to enhance bone mineralization (WB and strengthening)