| Disease | ALP | Ca | Phos | PTH |
|---|---|---|---|---|
| HyperPTH | (\uparrow) | (\uparrow) | (\downarrow) | (\uparrow) |
| Osteomalacia | (\uparrow) | (\downarrow) | (\downarrow) | (\uparrow) |
| osteoporosis | N | N | N | N |
| Paget’s | (\uparrow) | N | N | N |
| Bone mets | (\uparrow) | (\uparrow) | N | (\downarrow) |
Calcium biochemistry
- Calcium values dependant on albumin (protein bound component)
- If albumin low cannot use adjusted calcium so use ionised calcium instead
Phosphate biochemistry
- Predominantly intracellular
- ATP, DNA backbone, membrane phospholipids
Homeostasis of calcium and phosphate
- PTH and vitamin D and metabolites controlling factors
- Balance of - GI absorption, Bone storage/resorption, renal excretion/reabsorption
Parathyroid hormone
Net effect:
- Increase serum calcium
- Decrease serum phosphate
PTH causes osetoclasts to breakdown Bone releasing Ca and PO4
(\hookrightarrow) kidneys increase reabsorption of Ca but increase PO4 excretion
Kidneys also increase active form of vitamin D to absorb more from gut