Calcium Metabolism Flashcards
Serum conc of calcium
2.2-2.6
Serum conc of phosphate
0.7-1.4
Magnesium serum conc
0.8-1.2
Organ systems ca metabolism
Skeleton
Kidney
Gi tract
Calcitrophic hormones
Parathyroid hormone
Calcitonin
Vitamin D
Parathyroid hormone related protein
Forms of circulating calcium
Protein bound-inactive,not excreted
Ionized-active,excreted
Complexed with phosphate,bicarbonate and citrate
Calcium is
Essential
Calcium balance
Input=output
Negative balance of calcium
Osteoporosis
Calcium means of transport into cell
Translocation across cell membrane ,Er,mitochondria
Ca atpase
Feedback inhibition of ca
Decreased ca->increased pth-> stimulate kidney->vit d->git->release ca.
Also pth-> bone resorption-> ca
Parathyroid hormone structure
Prepropth(115aa)->propth->(90aa)->cleaved at position 6/7 ->84 residues(mature peptide)
Factors that regulate pth synthesis
Calcium regulates secretion and transcription. Inversely proportional
Transcription Inhibited by high vt D
Pth function
Increases calcium
Decreases inorganic phosphate by excretion
Bone components
Organic -33%- collagen,structural proteins like proteoglycans,phosphoproteins,osteocalcin
Inorganic-67%-hydroxyapatite with some calcium phosphate
Osteoblast function
Bone formation
Bone mineralization
Formation of matrix proteins
Activation of osteoclast by producing RANKL
Function of osteoclast
Resorption of bone
RANKL TO RANK which causes differentiation into osteoclasts
Osteoblast encased in bone
Osteoclast
Osteoblasts have receptors for
Pth
Vit d
Growth factors
Cytokines
Pth
Is trying to cause bone resorption
Prevents osteoblast to osteocyte
Promotes osteoblast to osteoclast
Promotes osteoblast activation of osteoclast
Pth site of action on kidney
Acts on pct (80%)and dct (20%)but primarily on dct bc pct reabsorption is vis osmosis
Calcitonin produced by
Parafollicar c cells
32aa
Calcitonin fxn
Inhibits bone resorption
Aids calcium excretion
Activationof vit d
Skin->liver->kidney
7dehydrocholesterol->cholecalciferol->25hydroxycholecalciferol when acted on by 25 hydroxylase->1,25dihydroxycholecalceferol when acted on by 1 alpha hudroxylase
How does activated vit d work
Activated vit d->binding to receptor on intestines->transcription of genes ie calbindin->transporter of ca
Nongenomic-allows ca through luminal brush border
Vit d deficiency
Rickets in children
Osteomalacia-most prominent
Deficiency in alpha 1 hydroxylsse
Vitamin d resistant rickets
Hypoplastic teeth
Retarded eruption
Pthrp isoforms
3
138,141,173 due to alternative splicing
Pthrp
Can activate pth receptor
Functions of pthrp
Tranfer calcium to milk
Fetal development
Can cause hypercalcemia of malignancy
Causes of hypocalcemia
Idiopathic After exposure to radiation Postoperative Vit d deficiency Malabsorption Liver dx Kidney dx Vit d resistance Psiedohyperparsthyroidsm-pth resistance
Psuedoparathroidsm symptoms
Hypocalcemia Hyperphosphatemia Tetany Siezures Hypoplasia of enamel Absence of eruption
Causes of hypercalcemia
Common
Hyperparathyroidsm
Malognancy
Vit d intoxication
Uncommon
Renal failuire
Sarcoidosis
Multiple myeloma
Symptoms of hypetcalcemia
Bone ache Muscle weakness Arrhythmia Lethargy Depression Confusion
Common sumptom of hypercalcemia
Pain in bones
Stones
Abdominal pain
Treat hypercalcemia of malignancy with
Bisphosphatones. Inhibits osteoclastic activity
Treatment of serum ca>3
Nacl iv
Osteoporosis
Reduction in bone mineral density for age,srx group
Factors affecting peak bone mass
Gender-Males>females Race-blacks>white Genetic Gonadal steroids-increase pbm Groth hormone Calcium intake Excercise
Sequale of osteoporosis
Dowagers hump
Loss of 6-9inches in height in upper thoracic vertebra
Treatment of osteoporosis
Estrogen treatment-inhibit osteoclast activity
Intake of calcium Excercise daily Bisphosphatones Calcitonin Vit d Pth (forteo)
