What percent of calcium is stored in bone and as what type?
99% as crystalline form, bone and teeth
Resorption of bone/Ca is stimulated by ____ and inhibited by ____
stim: PTH, Vit. D
Inhib: Calcitonin
How much calcium is stored in bone?
4000 mg
What percent of calcium is absorbed in the GI?
20%
how much calcium is in the ECF?
10 mg/dl, 1%
Of the free calcium, what percent is ionized and active?
50%
0.9% of ECF calcium is stored in…
soft tissue, ER, mitochondria, membranes
0.1% of ECF calcium is stored in
1/2 bound: bicarb, albumin, phosphate
1/2 free
Kidneys filter ____ mg of Ca per day, making up ___% of filtered load
10,000 mg filtered
98% of filtered load
how much calcium is free and bound in blood?
8.6-10.6 mg/dl
what hormone increases intestinal absorption of calcium?
vitamin d (1,25 dihydroxy)
PO4 represents ___ % of filtered load. The kidney can reabsorb ____% of PO4 when needed…
10% of FL
70-100% can be reabsorbed
What percent of phsophate can be found in bone/teeth, and what percent in muscle?
85% bone/teeth
15% muscle
In cells ___% of phosphate is in mitochondria
80%
Calcium and PO4 are regulated by which two hormones?
Vitamin D and PTH
calcium and PO4 levels require coordinated action of what 3 tissue types?
bone, intestine, kidney
PTH is released by what cell type of the parathyroid gland?
chief cells
What inhibits the activity of PTH?
rising Ca levels
Mechanism of PTH secretion from chief cells?
Hypocalcemia →
Parathyroid Stimulation →
PTH Release →
PTH Acts on Bone, Intestine, Kidney →
↑ Ca
Which pool of calcium in bone?
- mature mineralized
- hydroxyapatite
- reabsorption, slow breakdown into ECF
Stable pool
Which pool of calcium in bone?
- bone fluid in canaliculi
- amorphous crystals
- osteolytic osteolysis, fast release of ca and po4
labile pool
What separates bone from plasma within the canals?
osteocytic-osteoblastic membrane
In the labile pool, what moves calcium and po4 into the plasma in the central canal?
PTH activated calcium pump in osteocytic-osteoblastic membrane
PTH targets osteoblasts which regulate osteoclast activity by releasing what two substances?
OPG and RANKL/OPGL
What occurs when OPGL/RANKL alone bind osteoclasts?
bone resorption
What happens if OPG is co-released with OPGL/RANKL?
it binds OPGL/RANKL, preventing sesorption
A mutation in which gene would decrease osteoblasts and bone ossification?
RUNX2
What condition occurs as an autosomal dominant mutation in RUNX2?
cleidocranial dysplasia
PTH has what two effects on the kidney?
increase calcium absorption
decrease PO4 reabsorption
What enzyme does PTH stimulate, allowing activation of vitamin D?
1-alpha-hydroxylase
This hormone targets intestine, bone, kidney to regulate calbindin synthesis
vitamin d
Where is vitamin D first activated by hydroxylation of C25?
liver
Where does vitamin D receive its second hydroxylation on C1, leading to full activation to 1,25 dihydroxy?
kidney
How is vitamin d deactivatied?
hydroxylation on C24
What is the role of vitamin D in bone?
+ PTH stim. Resorption & Remodeling
What role does vitamin D have in the kidney?
Reabsorption of Ca2+ in DT and PO4 Reabsorption in PT
What role does vitamin D have in small intestine?
↑ Calbindin → ↑ Ca-ATPase Activity
What hormone has the following characteristics?
May prevent postprandial hypercalcemia
Deficiency idoes not lead to hypercalcemia
Excess does not produce hypocalcemia
May protect against excessive bone resportion
Calcitonin
What role does calcitonin have, and where
bone and kidney
inhibits bone resorption and tubular reabsorption
What Condition?
PTH: Increased Vit. D: Increased Plasma: Hypercalcemia, hyperphosphatemia Urine: ↑ Phosphate, cAMP, Ca2+ Bone Resorption: Increased
primary hyperPTH
“stones, bones, groans”
What Condition?
PTH: Decreased Vit. D: Decreased Plasma: Hypocalcemia, Hyperphosphatemia Urine: Decreased PO4 & cAMP Bone Resorption: Decreased
hypoPTH, surgical
What condition?
PTH: Increased Vit. D: Decreased Plasma: Hypocalcemia, Hyperphosphatemia Urine: Decreased PO4 & cAMP Bone Resorption: Decreased (defective Gs)
Pseudohypoparathyroidism (Albright’s Heredetary Osteodystrophy)
What condition?
PTH: Decreased Vit. D: NC (no intestinal Fx) Plasma: Hypercalcemia, Hypophosphatemia Urine: Increased Ca, PO4 & cAMP Bone Resorption: Increased
Humoral Hypercalcemia of Malignancy
Which disease has the following S/S?
Short stature, short neck
Obesity
Shortened 4th metatarsals and metacarpals
Pseudohypoparathyroidism (Albright’s Heredetary Osteodystrophy)
Which disease has the following S/S?
Tetany
Hyperreflexia, twitching, cramps
Convulsions
Trousseau sign
Hypoparathyroidism: Surgical
Which disease has the following S/S?
Osteoporosis, osteomalacia
Kidney stones
Muscle weakness, decreased excitability
Primary Hyperparathyroidism: Stones, Bones, & Groans
Which disease has the following S/S?
Tetany
Muscle weakness
Greenstick fractures
Skeletal abnormality: bow legs, wrists
Rickets - Deficiency of Vitamin D in Childhood
Which disease has the following S/S?
Soft, weak bones
Frequent fx
Hypocalcemic tetany
hypocalcemia
Ostoemalacia: Deficiency of Vit. D in Adulthood