What is Hypoparathyroidism?

Hypoparathyroidism (HPTH) is a rare endocrine condition that affects the levels of parathyroid hormone (PTH) in children and adults, causing low levels of calcium in the blood. PTH is secreted by the parathyroid glands in the neck whose normal function is to automatically regulate calcium levels. 

Hypoparathyroidism may be due to a congenital, genetic or autoimmune disorder which affects the function of the parathyroid glands or it may occur as the temporary or permanent result of surgery to the neck where there is removal of, or damage to, the glands.

These conditions all cause insufficient or inactive levels of parathyroid hormone (PTH) to be secreted into the blood. Low PTH levels, or Hypoparathyroidism,  lead to low levels of calcitriol and calcium and high levels of phosphate in the blood which cannot be regulated automatically by the parathyroid glands, as happens normally.

Calcium is vital to life and affects every cell in the body. Lack of it is felt both physically, emotionally and neurologically. Even small variations from the norm can impair nerve and muscle function. Hypocalcaemia, affects the energy levels, nerves, muscles, eyes, bones, kidneys & heart so people with HPTH need lifelong medication. Treatment is with vitamin D and calcium supplements and global trials of replacement parathyroid hormone treatment are currently taking place. Calcium levels must be regularly monitored to maintain stability, prevent crises and to keep the body functioning correctly.

What do parathyroid glands do?

In your neck, just behind the butterfly shaped thyroid gland, lie four tiny yellow parathyroid glands. 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'.

Shown here, these tiny yellow glands, about the size of a grain of rice, play a vital role in the body. They continually monitor the amount of calcium in the blood as it flows through them and they make constant adjustments to keep the calcium levels stable.

How do they keep calcium levels stable?

Calcium levels fluctuate constantly in response to a number of factors and parathyroid glands secrete parathyroid hormone (PTH) into the blood which helps to regulate them. Normally, if the levels of calcium in the blood 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 taken - the bones release more calcium into the blood, the intestines absorb more calcium from food and the kidneys reduce the calcium and increase the phospate we excrete in our urine.  Calcium levels begin to rise. This process also works in reverse when calcium levels are too high and is called a feedback mechanism. This mechanism prevents calcium levels from getting out of control.

Why is calcium so important?

Calcium affects every cell in the body. Most people usually think about teeth and nails in connection with calcium but in fact it's effects are on the whole body. Low and high calcium levels produce a spectrum of physical, emotional and neurological symptoms. Calcium works with phosphorous to produce energy within the body. It helps blood to clot and is important in the correct functioning of nerves and muscles as well as the kidneys and heart. This is why lifelong treatment for Hypoparathyroidism is necessary and why calcium levels must  be monitored so carefully.

How is vitamin D involved?

Vitamin D3 is converted in the liver (into 25 D3 or calcidiol) and again in the kidney into the active form of vitamin D ( 1.25 or calcitriol) which is really a hormone. Normally, parathyroid hormone provides the drive for this last conversion and both calcitriol and parathyroid hormones then work together to regulate calcium levels and prevent them getting out of control. 

So - what happens in Hypoparathyroidism?

In Hypoparathyroidism there is not enough parathyroid hormone  - nor enough calcitriol. A double whammy. Without enough parathyroid hormone, the body cannot make calcitriol and the feedback mechanism cannot work so calcium levels cannot be regulated.  Medication is needed to replace the calcitriol. but as the feedback mechanism itself cannot work, doses of calcitriol have to be titrated or measured against the levels of calcium by means of blood tests. A certain amount of guesswork inevitably take place and patients can help themselves by monitoring their symptoms which are a useful guide to understanding when medication may need to be adjusted.

How is Hypoparathyroidism diagnosed?

Diagnosis is by blood tests. In Hypoparathyroidism, blood calcium level is low, blood phosphate level is high, and  parathyroid hormone level is low. If tests show these results, the patient will be referred to an endocrinologist at the local hospital. Further blood tests on thyroid function, kidney function, liver, bone profile, and vitamin D levels will all be done at the first appointment. A bone scan, kidney scan and a 24 hour urine test may also  be requested.

* Intro to lectures from Prof John Landon quoted in 'The Endocrine System' by Hinson, Raven & Chew (Elsevier 2006)

For further information please see Research on HPTH and Related Articles

© HPTH UK 2010