Calcium metabolism
The two hormones which primarily control calcium metabolism are:
Other hormones include
Actions of parathyroid hormone
Actions of 1,25-dihydroxycholecalciferol
*this is actually via an indirect mechanism as osteoclasts don't have PTH receptors
- parathyroid hormone (PTH)
- 1,25-dihydroxycholecalciferol (calcitriol, the active form of vitamin D)
Other hormones include
- calcitonin: secreted from the parafollicular cells (C-cells) of the thyroid gland
- thyroxine
- growth hormone
Actions of parathyroid hormone
- increases plasma calcium, decreases plasma phosphate
- increases renal tubular reabsorption of calcium
- increases osteoclastic activity*
- increases renal conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol
- decreases renal phosphate reabsorption
Actions of 1,25-dihydroxycholecalciferol
- increases plasma calcium and plasma phosphate
- increases renal tubular reabsorption and gut absorption of calcium
- increases osteoclastic activity
- increases renal phosphate reabsorption
*this is actually via an indirect mechanism as osteoclasts don't have PTH receptors