Also, people with the genetic disease DiGeorge syndrome, often born with parathyroid glands that are too small and can't produce enough parathyroid hormone.
Now, even though parathyroid hormone stimulates bone resorption, it's been found that intermittent injections with teriparatide activates osteoblasts more than osteoclasts, therefore increasing bone formation.
Lastly, parathyroid hormone increases calcium reabsorption and reduces the reabsorption of phosphate from the kidneys, so more phosphate is excreted through the urine.
This can result in conditions like primary hyperparathyroidism which result in too much parathyroid hormone, which leads to excess phosphate being excreted in the urine.
Related to this is pseudohyporparathyroidism, which is where the kidneys simply don't respond to parathyroid hormone because of a genetic defect in the parathyroid hormone receptor.
If calcium levels fall, the four parathyroid glands buried within the thyroid gland release parathyroid hormone which frees up both calcium and phosphate ions from the bones.
Less calcium entering the blood is the most common cause and can be due to hypoparathyroidism, or lower levels or lower activity of parathyroid hormone.
We have teriparatide, which is a parathyroid hormone analogue that also reduces fracture risk and increases bone mineral density in patients with osteoporosis.
So when the dust settles, as a result of parathyroid hormone, phosphate is lost in the urine while ionized calcium is kept in the blood, so ionized calcium levels rise and phosphate levels fall!
Bone remodelling as a whole is highly dependent on serum calcium levels, which, in turn, are kept in the normal range by a balance between parathyroid hormone, or PTH, calcitonin and vitamin D.