Some cancer treatments can cause low calcium levels in the blood. This is called hypocalcaemia (pronounced high-po-kal-seem-ee-ah).
Why people with cancer get low blood calcium
Having low calcium is rare in people with cancer. It can be a temporary side effect of some cancer treatment drugs, such as cisplatin and doxorubicin.
The main cause of low calcium levels is having the parathyroid glands in your neck removed. This might be necessary for some types of cancer in the neck area. It can also happen if the parathyroid glands are damaged during thyroid gland surgery. Or during other types of surgery to the head and neck.
After head and neck surgery, you could have permanently low calcium levels. But they could also go back to normal after a few months.
What are the parathyroid glands?
The parathyroid glands help to keep a steady level of calcium in the blood. We have 4 parathyroid glands in the base of our necks. They're tiny and close to the thyroid gland.
The position of the glands makes it difficult for a surgeon to remove the thyroid without damaging or removing the parathyroid glands during the operation.
The parathyroid glands make parathyroid hormone (PTH). Normally when the level of calcium in the blood drops, the parathyroid glands make more PTH. This increases the amount of blood calcium by making the:
- bones release calcium into the blood
- kidneys take more calcium back into the blood when urine is being made
- intestines absorb more calcium from food
If the parathyroid glands have been removed or damaged, your body won’t produce enough PTH. So your calcium levels can fall below normal.
This is called hypoparathyroidism (high-po-para-thi-royd-ism).
Symptoms of low blood calcium
Many people don’t have any symptoms when their calcium levels are low. After surgery for thyroid cancer, your surgeon will check your blood calcium levels before you leave hospital.
You will also have regular check ups and blood tests to check your calcium levels. So your doctor may tell you that you have low calcium before you have any symptoms.
Symptoms of low calcium include:
- painful muscle spasms and cramps
- twitching of muscles
- numbness or tingling in feet and hands
- numbness or tingling around the mouth
Untreated low calcium can lead to more severe symptoms, such as:
- dry skin
- fits (seizures), this is very rare
Talk to your doctor if you have any of these symptoms.
Treatment for low blood calcium
Your doctor will prescribe calcium and vitamin D tablets for you if your blood calcium level is low. This usually keeps your blood calcium at a normal level. Eating foods with high levels of calcium will also help.
You will need to have calcium directly into the blood through a drip (intravenous infusion) if you have sudden symptoms of low blood calcium after head and neck surgery.
Help and support
Cancer Research UK
The organisation Hypopara UK offers information and support if you have hypoparathyroidism.