| indogenous agents | ||||
| A) major | ||||
| agent | main action | mechanism | control | comments |
| PTH | hypercalcemic hor (+ serum Ca level) | 1-+ bone resorption (+ Ca trans from bone to bl) so + osteoclasts activity () Ca resorption 2-() renal Ca exc 3-+ renal exc of P | it is controlled when hypocalcemia | *it is poly peptide sec from parathyroid gland *parathormone is not used as drug so hypoparathyrodism treated by Ca I.V or vit D *toxicity >hyperparathyrodism >osteoporosis |
| Vit D | hypercalcemic agent (+ serum Ca level) | 1-+ intest abs of P & Ca 2-() renal exc of Ca & P | *sources of vit D a) dietary D2 >ergocalciferol (plant origin) b) cholecalciferol D3 from action of UV light on skin (7-hydrocholesterol) | |
| B)minor | ||||
| Calcitonin | Hypocalcemic hor | 1-() bone resorption 2-+ renal exc of Ca & P | +bl Ca level will stim sec | polypeptide sec from thyroid gland *function only on Ca metab >C3 cells of thyroid gl *uses : 1-t of Paget's disease (disease of bone associated e + thickening and calcifecation) 2-T of Neoplacia >tumour of bone **preps :a)human calcitonin b)salmon calcitonin >more potent ,stable + longer duration than human (IM ,SC or intranasal **side effects 1-nausia & vimmiting 2-local inf at site of injectn 3-Tingling sensation in hands 4-facial flushing 5-unpleasent taste in the mouth |
| Estrogen | delay or prevent bone loss (osteoporosis) in postmenopausal women due to () PTH induced bone resorption | |||
| glucocorticoids | systemic chronic use may lead to osteoporosis > lead to 1 -ve Ca balance 2- osteoclast activity | |||
| Exogenous | ||||
| Bisphosphanates | () osteoclast activity so () bone resorption | *it is poly phosphate organic cpd eg Etidronate and Pamidronate *used in T of osteoporosis | ||
| F- | chronic exposure to high % of f + new bone syn | present in drinkind water and dental pastes (prevent dental caries) | ||
| thiazide diuretics | () renal exc of Ca (so contraindicated in case of hypercalcemia) | |||
| Flurosemide (lasix) | diuretic + renal Ca exc so used in ttt of hypercalcemia (( as glucocorticoids -ve Ca balance)) | |||
| Plicamycin (mithramycin) | () osteoclast activity so () bone resorption (as Bis) | *it is cytotoxic antibiotic so ttt of cancer *ttt of paget's & hypercalcemia (as calcitonin) | ||