What organs are affected by calcium?

Overview — Rickets and osteomalacia

Adults can experience a similar condition, which is known as osteomalacia or soft bones.

What causes rickets?

A lack of vitamin D or calcium is the most common cause of rickets. Vitamin D largely comes from exposing the skin to sunlight, but it’s also found in some foods, such as oily fish and eggs. Vitamin D is essential for the formation of strong and healthy bones in children.

In rare cases, children can be born with a genetic form of rickets. It can also develop if another condition affects how vitamins and minerals are absorbed by the body.

Who’s affected?

Rickets was common in the past, but it mostly disappeared in the western world during the early 20th century after foods like margarine and cereal were fortified with vitamin D.

However, in recent years, there’s been an increase in cases of rickets in the UK. The number of rickets cases is still relatively small, but studies have shown a significant number of people in the UK have low levels of vitamin D in their blood.

Any child who doesn’t get enough vitamin D or calcium either through their diet, or from sunlight, can develop rickets. But the condition is more common in children with dark skin, as this means they need more sunlight to get enough vitamin D, as well as children born prematurely or taking medication that interferes with vitamin D.

Treating rickets

For most children, rickets can be successfully treated by ensuring they eat foods that contain calcium and vitamin D, or by taking vitamin supplements.

Some families are eligible for free vitamin supplements from the government’s Healthy Start scheme – find out if you’re eligible and how to apply.

If your child has problems absorbing vitamins and minerals, they may need a higher supplement dose or a yearly vitamin D injection.

Preventing rickets

Rickets can easily be prevented by eating a diet that includes vitamin D and calcium, spending some time in sunlight, and if necessary, taking vitamin D supplements.

Read more about:

• preventing rickets
• who should take vitamin D supplements
• how much vitamin D adults, children and babies need

When to seek medical advice

Take your child to see your GP if they have any of the signs and symptoms of rickets.

Your GP will carry out a physical examination to check for any obvious problems. They may also discuss your child’s medical history, diet, family history, and any medication they’re taking.

A blood test can usually confirm a diagnosis of rickets, although your child may also have some X-rays or possibly a bone density scan (DEXA scan). This is a type of X-ray that measures the calcium content in bones.

If you’re an adult and you’re experiencing bone pain or muscle weakness you should also see your GP to get it checked out.

Page last reviewed: 05 August 2021
Next review due: 05 August 2024

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Parathyroid hormone

Parathyroid hormone is secreted by the parathyroid glands and is the most important regulator of blood calcium levels.

Alternative names for parathyroid hormone

PTH; parathormone; parathyrin

What is parathyroid hormone?

The parathyroid glands are located in the neck, just behind the butterfly-shaped thyroid gland.

Parathyroid hormone is secreted from four parathyroid glands, which are small glands in the neck, located behind the thyroid gland. Parathyroid hormone regulates calcium levels in the blood, largely by increasing the levels when they are too low. It does this through its actions on the kidneys, bones and intestine:

1. Bones – parathyroid hormone stimulates the release of calcium from large calcium stores in the bones into the bloodstream. This increases bone destruction and decreases the formation of new bone.
2. Kidneys – parathyroid hormone reduces loss of calcium in urine. Parathyroid hormone also stimulates the production of active vitamin D in the kidneys.
3. Intestine – parathyroid hormone indirectly increases calcium absorption from food in the intestine, via its effects on vitamin D metabolism.

How is parathyroid hormone controlled?

Parathyroid hormone is mainly controlled by the negative feedback of calcium levels in the blood to the parathyroid glands. Low calcium levels in the blood stimulate parathyroid hormone secretion, whereas high calcium levels in the blood prevent the release of parathyroid hormone.

What happens if I have too much parathyroid hormone?

A primary problem in the parathyroid glands, producing too much parathyroid hormone causes raised calcium levels in the blood (hypercalcaemia) and this is referred to as primary hyperparathyroidism. There is a similar but much rarer condition called tertiary hyperparathyroidism that causes hypercalcaemia due to excess parathyroid hormone production on the back drop of all four glands being overactive. Secondary hyperparathyroidism occurs in response to low blood calcium levels and is caused by other mechanisms, for example, kidney disease and vitamin D deficiency.

Mild primary hyperparathyroidism often causes few if any symptoms and is frequently diagnosed by finding a high calcium concentration on a routine blood test. Treatment may be by surgical removal of the affected gland(s) (parathyroidectomy). Further information on the symptoms for each condition can be found in the individual articles.

What happens if I have too little parathyroid hormone?

Too little parathyroid hormone or hypoparathyroidism, is a rare medical condition. It can result in low levels of calcium in the blood (hypocalcaemia). It is usually treated medically with oral calcium and vitamin D analogues but the availability of parathyroid hormone replacement therapy may change the approach to treatment for some patients.

Last reviewed: Dec 2020

Your body and calcium

Calcium is an important mineral that our bodies need to keep us healthy. Having cancer can affect the amount of calcium in the body.

Why do we need calcium?

Nearly all the calcium in the body is stored in bone tissue. A small amount circulates in our blood and other body fluids. There is also some inside our cells.

We need calcium to:

• build and keep our bones and teeth healthy
• help our blood clot
• regulate some of the normal functioning of the brain and spinal cord (central nervous system)
• keeping our muscles working properly

Where we get calcium from

We need to get calcium from our diet. Foods which contain calcium include:

• dairy products such as eggs, milk, butter and cheese – this is where most of our calcium comes from
• green leafy vegetables such as broccoli, kale and spring greens
• soya beans
• tinned oily fish such as sardines with bones
• calcium fortified cereals and drinks

Normal calcium levels

The level of calcium in the blood is normally between 2.1 mmol per litre and 2.6 mmol per litre. But remember that blood levels can vary a little from person to person.

You might need treatment if your calcium level goes above or below these levels.

What happens to calcium in the body?

Our bodies absorb calcium from the food we eat through the lining of the bowel. The calcium is stored in our bones. The body controls the amount of calcium in the bloodstream very carefully. When blood levels of calcium fall too low, the bones release calcium into the blood. The amount of calcium the bowel absorbs from food increases and the kidneys get rid of less calcium through the urine.

The opposite happens if blood levels of calcium get too high.

There are 3 hormones in the body that play an important role in keeping the correct balance of calcium in the blood. These are:

• parathyroid hormone (PTH) – made by the parathyroid glands in the neck
• calcitonin
• vitamin D

Blood calcium levels that are too high or too low can cause serious problems.

Having too much calcium in the blood is called hypercalcaemia. This is pronounced hyper-kal-seem-ia. Not having enough calcium is called hypocalcaemia. This is pronounced hypo-kal-seem-ia.

The main causes of hypercalcaemia include:

• too much parathyroid hormone in the blood
• some types of cancer
• your kidneys not being able to get rid of excess calcium
• endocrine diseases
• some medicines

• FInd out more about high calcium levels in people with cancer

A low calcium level is rare in people with cancer. The main causes of having a low level of calcium in the blood include:

• removal of your parathyroid glands or damage to them when having surgery to the head and neck area
• some medicines
• vitamin D deficiency

• Find out more about low calcium levels

References

• Hypercalcaemia of Malignancy BMJ Best Practice, December 2021
• Assessment of hypocalcaemia BMJ Best Practice, 2021
• Assessment of hypercalcaemia BMJ Best Practice, 2020
• Cancer and its management (7th edition)
  J Tobias and D Hochhauser
  Wiley-Blackwell, 2015
• Ross and Wilson anatomy and physiology in health and illness (12th edition) A Waugh and A Grant Elsevier, 2014