Activating Calcium-Sensing Receptor Mutations
What is Activating Calcium-Sensing Receptor Mutations?
Activating calcium-sensing receptor mutations are a rare genetic condition. Your body has tiny sensors in your parathyroid glands that detect calcium levels in your blood. These sensors tell your body when to release or hold back parathyroid hormone, which controls calcium.
In this condition, the sensors are overly sensitive. They think your calcium is too high even when it is actually low or normal. This tricks your parathyroid glands into making less hormone than you need. The result is low calcium levels in your blood, called hypocalcemia, and high calcium in your urine, called hypercalciuria.
Most cases are inherited in an autosomal dominant pattern. This means you only need one changed gene from one parent to have the condition. Sometimes the mutation happens for the first time in you, with no family history. The condition can range from mild to severe depending on how sensitive your calcium sensors have become.
Symptoms
- Muscle cramps, twitching, or spasms
- Tingling or numbness in fingers, toes, or around the mouth
- Fatigue and weakness
- Seizures in severe cases
- Abnormal heart rhythms
- Kidney stones from high calcium in urine
- Dry skin and brittle nails
- Anxiety or mood changes
Some people with mild forms of this condition have no symptoms at all. Others only notice problems during times of stress, illness, or pregnancy when calcium demands increase.
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Causes and risk factors
This condition is caused by mutations in the CASR gene. This gene provides instructions for making the calcium-sensing receptor protein. When the gene is changed, the receptor becomes too active. It signals your parathyroid glands to reduce hormone production even when calcium is already low. The mutation is usually inherited from one parent who has the condition. In some cases, the mutation occurs spontaneously during early development.
Risk factors include having a parent with the condition, a family history of unexplained low calcium, or a history of kidney stones at a young age. The condition affects males and females equally. There are no lifestyle or environmental factors that cause this genetic change. However, low vitamin D, certain medications, or high phosphorus intake can make symptoms worse in people who already have the mutation.
How it's diagnosed
Diagnosis starts with blood tests that measure calcium and parathyroid hormone levels. In this condition, calcium is low or low-normal, but PTH is also low or inappropriately normal. This pattern is unusual because PTH should be high when calcium is low. A urine test will show high calcium excretion. These findings together suggest the calcium-sensing receptor is overly active.
Rite Aid offers add-on testing for Parathyroid Hormone to help identify this pattern when combined with your calcium results. Genetic testing can confirm the diagnosis by identifying mutations in the CASR gene. Your doctor may also check magnesium, phosphorus, and vitamin D levels to rule out other causes of low calcium. Kidney function tests help assess if high urine calcium has caused any damage.
Treatment options
- Calcium supplements to raise blood calcium levels
- Active vitamin D supplements to help absorb calcium
- Thiazide diuretics to reduce calcium loss in urine and protect kidneys
- High-calcium diet including dairy, leafy greens, and fortified foods
- Adequate hydration to prevent kidney stones
- Regular monitoring of blood calcium, PTH, and kidney function
- Avoid high-salt diets which increase calcium loss in urine
- Genetic counseling for family planning decisions
Need testing for Activating Calcium-Sensing Receptor Mutations? Add it to your panel.
- Simple blood draw at your nearest lab
- Results in days, not weeks
- Share results with your doctor
Frequently asked questions
This is a rare genetic condition where your calcium sensors are too sensitive. They tell your body to lower calcium even when levels are already low. This leads to low calcium in blood and high calcium in urine.
Blood tests showing low calcium with low or normal PTH levels are the first clue. Most conditions that lower calcium cause high PTH, so this unusual pattern raises suspicion. Genetic testing can confirm the diagnosis by finding mutations in the CASR gene.
Yes, most cases are inherited in an autosomal dominant pattern. You need only one changed gene from one parent to have it. Sometimes the mutation happens for the first time in you with no family history.
Common symptoms include muscle cramps, tingling in your fingers or toes, fatigue, and weakness. Some people get kidney stones from high calcium in urine. Severe cases can cause seizures or heart rhythm problems.
There is no cure because it is a genetic condition. Treatment focuses on managing symptoms and preventing complications. Most people do well with calcium and vitamin D supplements plus medications to reduce urine calcium loss.
Your doctor will recommend regular blood tests to monitor calcium, PTH, and kidney function. Testing frequency depends on your symptoms and how well controlled your levels are. Many people need testing every 3 to 6 months.
Untreated low calcium can cause serious problems. You may develop severe muscle spasms, seizures, or dangerous heart rhythms. High urine calcium can lead to kidney stones and eventually kidney damage if not managed properly.
Yes, eating calcium-rich foods helps raise blood calcium levels. Include dairy products, leafy greens, and fortified foods in your diet. Stay well hydrated and limit salt, which increases calcium loss in urine.
Each child has a 50% chance of inheriting the mutation if you have it. Genetic counseling can help you understand the risks and options. Testing during pregnancy or early childhood can identify the condition before symptoms appear.
Both cause low calcium and low PTH, making them look similar. The key difference is the cause. Hypoparathyroidism means your parathyroid glands do not work properly. In this condition, the glands work fine but are getting false signals from overly sensitive calcium sensors.