Key hormonal regulators of serum calcium and their actions
| Regulator | Actions |
|---|---|
| PTH | Increases bone reabsorption by osteoclasts* |
| Increases renal absorption of filtered calcium | |
| Stimulates conversion of 25(OH)D to 1,25(OH)D (activated vitamin D, also called calcitriol) | |
| 1,25(OH)D | Increases bone reabsorption by osteoclasts |
| Increases renal tubular reabsorption of filtered calcium | |
| Increases intestinal absorption of calcium via active transport | |
| Calcitonin (thought to be of little physiological significance beyond the neonatal period) | Inihibits bone reabsorption by osteoclasts |
| Reduces renal absorption of filtered calcium | |
| Decreases intestinal absorption of calcium |
The boldface emphasises the categorisation of hypercalcaemia as being related to bone, kidney, or gut.
*The mechanisms of PTH on bone metabolism are complex; here we provide a simplified overview.
PTH, parathyroid hormone.