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Familial hypocalciuric hypercalcemia (FHH) can cause a few symptoms that also happen in primary hyperparathyroidism (PHPT). But, there are many differences between the two medical conditions.

A medical evaluation is key for those who display symptoms of FHH and/or PHPT. After getting an evaluation, people can find out if either of these conditions are causing their symptoms and receive appropriate treatment.

What Is Familial Hypocalciuric Hypercalcemia?

FHH is an inherited disorder that causes the blood calcium level to rise. It can also cause low to moderate levels of calcium in urine.

There are three types of FHH. Each one is associated with a gene that impacts the body’s ability to regulate its blood calcium level.

Type 1 is the most common form of the condition. It is linked to changes in the calcium-sensing receptor (CaSR) gene, which tracks and regulates calcium in the blood.

Comparatively, Type 2 is related to changes in the GNA11 gene, which works with the CaSR gene to manage processes that regulate the body’s calcium level. Meanwhile, Type 3 is caused by changes in the AP2S1 gene; these changes can impact calcium homeostasis.

Familial Hypocalciuric Hypercalcemia Symptoms

Symptoms of FHH can be similar to those of PHPT. They include:

  • Fatigue
  • Weakness
  • Difficulty concentrating
  • Excessive thirst

In rare instances, people dealing with the disorder can experience pancreatitis or calcium buildup in the joints.  PHPT patients often have a lot more symptoms.

Familial Hypocalciuric Hypercalcemia vs. Primary Hyperparathyroidism

FHH can be misdiagnosed as PHPT. This is due to the fact that both can manifest as hypercalcemia, while FHH in most cases presents with normal or high normal parathyroid hormone (PTH) levels and PHPT with above-average production of PTH.

Patients dealing with FHH experience a mutation of the CaSR, GNA11, or AP2S1 gene. Alternatively, patients can experience PHPT for any of the following reasons:

  • A noncancerous growth (adenoma) on one or more of the parathyroid glands
  • All 4 parathyroid glands enlargement (hyperplasia)
  • Cancerous tumor

As soon as FHH or PHPT symptoms appear, seek out medical treatment. From here, a patient can receive a medical evaluation to determine the cause of their symptoms.

Familial Hypocalciuric Hypercalcemia Diagnosis

Measuring the PTH level is a great first step to determine if a patient is dealing with hypercalcemia. If the PTH level is higher than normal, a patient may be dealing with PHPT.  If the PTH level is close to normal or in the normal range then FHH should also be considered.

PHPT is commonly diagnosed based on  elevated calcium & PTH levels. In this instance, the parathyroid glands are aiming for a higher calcium level then what the body needs, and produce excess PTH. Consequently, bone loss occurs, and calcium and phosphate are excreted into urine.  A 24 hour urine calcium collection usually shows normal or elevated amounts of calcium in the urine.

With FHH, 24 hour urine calcium levels are very low and comparison of the calcium vs. creatinine clearance by the kidney shows that calcium clearance is extremely low.  Diagnosis of FHH can be confirmed by doing genetic testing.

Familial Hypocalciuric Hypercalcemia Treatment

FHH does not usually require treatment, since the condition in most people tends to be asymptomatic or with minimal symptoms.

Dr. Babak Larian of the CENTER for Advanced Parathyroid Surgery can perform comprehensive testing to determine if a patient is dealing PHPT or FHH. If the parathyroid glands are functioning as expected, Dr. Larian may recommend genetic testing. That way, a patient can have confirmation that they have FHH.  If Dr. Larian finds PHPT, he will make a full assessment and identify which of the parathyroid glands are malfunctioning. He can perform a minimally invasive parathyroidectomy if indicated. Or,

Dr. Larian encourages anyone dealing with FHH or PHPT symptoms to meet with him for an evaluation. To book a free in-person or virtual consultation with Dr. Larian, please contact us online or call us today at 310-461-0300.

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