Familial Hypocalciuric Hypercalcemia (FHH)

What is Familial Hypocalciuric Hypercalcemia (FHH)?

Familial Hypocalciuric Hypercalcemia, or FHH, is a genetic condition that causes mildly elevated calcium levels in your blood. Despite the high calcium, your kidneys excrete very little calcium in your urine. This happens because of mutations in the calcium-sensing receptor gene, which normally helps your body regulate calcium levels.

FHH is typically benign, meaning it does not usually cause serious health problems. Most people with this condition never experience symptoms and live normal lives. The elevated calcium levels remain stable over time and rarely lead to complications.

FHH is different from primary hyperparathyroidism, another condition that causes high calcium. Understanding this difference is important because FHH does not usually require treatment, while hyperparathyroidism often does. Genetic testing and specific blood work can help doctors tell these conditions apart.

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Symptoms

Most people with FHH have no symptoms at all. The condition is often discovered during routine blood work when calcium levels come back slightly high.

Mild fatigue or weakness in some cases
Occasional muscle aches or joint pain
Increased thirst or urination in rare cases
Confusion or difficulty concentrating, though very uncommon
Kidney stones, though much less common than in other calcium disorders

Many people with FHH remain asymptomatic throughout their entire lives. When symptoms do occur, they are typically mild and easily overlooked.

Causes and risk factors

FHH is caused by inherited mutations in genes that control calcium sensing in your body. The most common mutation affects the calcium-sensing receptor gene, called CASR. This receptor normally tells your parathyroid glands and kidneys how much calcium is in your blood. When the receptor does not work properly, your body thinks calcium levels are lower than they actually are.

The condition follows an autosomal dominant inheritance pattern, meaning you only need one copy of the mutated gene to have FHH. If one parent has FHH, each child has a 50% chance of inheriting it. Less commonly, mutations in other genes like GNA11 or AP2S1 can also cause FHH. There are no lifestyle or environmental risk factors that cause this condition, as it is purely genetic.

How it's diagnosed

FHH is diagnosed through a combination of blood tests and medical history. Doctors look for mildly elevated calcium levels alongside normal or slightly elevated parathyroid hormone, or PTH. A 24-hour urine test showing low calcium excretion is another key finding. The calcium-to-creatinine clearance ratio helps distinguish FHH from primary hyperparathyroidism.

Rite Aid offers PTH testing as an add-on to our blood testing service, which can help identify abnormal calcium regulation. Genetic testing may also be recommended to confirm the diagnosis and identify the specific mutation. Family history is important, as FHH runs in families and multiple relatives often have mildly elevated calcium levels.

Treatment options

Most people with FHH do not need treatment because the condition is benign and rarely causes problems. Monitoring calcium and PTH levels periodically helps ensure levels remain stable.

No medications are typically needed for FHH
Avoid unnecessary parathyroid surgery, as it does not help FHH
Stay well hydrated to support kidney function
Maintain a balanced diet with normal calcium intake
Inform all healthcare providers about your FHH diagnosis
Regular check-ups to monitor calcium levels over time
Genetic counseling if planning to have children

The most important aspect of managing FHH is making sure it is not mistaken for primary hyperparathyroidism. Surgery to remove parathyroid glands will not fix FHH and should be avoided. Talk to your doctor if you have questions about your calcium levels or family history.

Frequently asked questions

FHH causes mildly elevated calcium with low urine calcium excretion due to genetic mutations. Primary hyperparathyroidism causes high calcium due to overactive parathyroid glands and typically shows higher urine calcium. FHH is benign and needs no treatment, while hyperparathyroidism often requires surgery. Blood tests and urine calcium measurements help doctors distinguish between the two.

Most people with FHH do not need any treatment because the condition is benign. Your calcium levels typically remain stable and do not cause health problems. Your doctor may recommend periodic monitoring to ensure levels stay consistent. The most important thing is avoiding unnecessary parathyroid surgery, which does not help FHH.

Kidney stones are uncommon in FHH, especially compared to other calcium disorders. The low urine calcium excretion that characterizes FHH actually reduces the risk of stone formation. If you have FHH and develop kidney stones, your doctor will investigate other possible causes. Staying well hydrated helps protect your kidneys.

FHH follows an autosomal dominant pattern, meaning each of your children has a 50% chance of inheriting the condition. If your child inherits the gene mutation, they will have FHH. Genetic counseling can help you understand inheritance patterns and testing options. Many families have multiple generations with mildly elevated calcium levels.

Diagnosis requires testing calcium, parathyroid hormone, and urine calcium levels. PTH is typically normal or slightly elevated in FHH. A 24-hour urine collection shows low calcium excretion. The calcium-to-creatinine clearance ratio helps distinguish FHH from other conditions.

FHH is present from birth because it is a genetic condition. However, it may not be discovered until adulthood during routine blood work. Calcium levels are typically stable throughout life. If calcium suddenly increases significantly, your doctor will look for other causes beyond FHH.

No, you should maintain a normal, balanced diet with regular calcium intake. Restricting calcium does not help FHH and may harm your bone health. Your body regulates calcium differently due to the genetic mutation, but dietary calcium is still important. Talk to your doctor about appropriate nutrition for your individual needs.

Your doctor will recommend a monitoring schedule based on your individual situation. Many people with FHH check calcium and PTH levels every one to two years. More frequent testing may be needed if you develop symptoms or if levels change. Regular monitoring helps ensure your calcium remains stable over time.

There is no cure for FHH because it is caused by a genetic mutation present in every cell. Fortunately, FHH is benign and does not usually require treatment or cause serious problems. Most people with FHH live normal, healthy lives without intervention. The focus is on proper diagnosis to avoid unnecessary treatments.

Misdiagnosis can lead to unnecessary parathyroid surgery that will not fix FHH. Surgery may remove healthy parathyroid tissue without correcting calcium levels. This is why careful testing, including urine calcium measurement and possibly genetic testing, is so important. Always get a second opinion before agreeing to parathyroid surgery if you have mildly elevated calcium.