Your parathyroid glands control the level of calcium in your blood. We need calcium to make our bodies work properly.
Where are the parathyroid glands?
The parathyroid glands lie in your neck, just behind the butterfly shaped thyroid gland. Sometimes they may also be found elsewhere in the body.
They are not related to the thyroid except by name ( ‘para’ comes from the Greek for ‘near’) and they have a completely different function from the thyroid.
Most people have four tiny yellow glands which are about the size of a grain of rice.
What do the parathyroid glands do?
Calcium levels fluctuate constantly in response to a number of factors such as food, drink, exercise, stress, infection and other medications. The job of the parathyroid glands is to continually adjust your calcium levels to keep them stable.
They do this by means of an automatic feedback system.
How does this feedback mechanism work?
If calcium levels begin to fall the parathyroid glands respond by increasing their output of parathyroid hormone (PTH) into the blood.
This acts along with calcitriol (vitamin D hormone) to send instructions to other parts of the body.
Three-way action is then taken:
- the bones release more calcium into the blood
- the intestines absorb more calcium from food
- the kidneys reduce the calcium and increase the phosphate we excrete in our urine
As calcium levels begin to rise this process works in reverse by decreasing the parathyroid hormone output so that calcium levels start to fall again.
This amazing feedback mechanism goes on all the time, day in, day out, to prevent calcium levels from getting out of control.
What happens if it goes wrong?
Sometimes, one or more of the parathyroid glands become over-active and begin to produce too much PTH due to a benign (non-cancerous) growth called an adenoma.
This results in calcium being removed from the bones and causes high blood calcium (hypercalcaemia) which causes problems and can make you feel unwell.
There are different conditions caused by over active parathyroid glands (hyperparathyroidism):