Nearly all adults with high calcium levels will have a parathyroid tumor, and just a few will have FHH. FHH is often diagnosed incorrectly. If you have been told that you may have FHH, read this page! What is FHH? Familial hypocalciuric hypercalcemia FHH is a very rare genetic condition that causes high blood calcium levels.
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Nearly all adults with high calcium levels will have a parathyroid tumor, and just a few will have FHH. FHH is often diagnosed incorrectly.
If you have been told that you may have FHH, read this page! What is FHH? Familial hypocalciuric hypercalcemia FHH is a very rare genetic condition that causes high blood calcium levels. It likely does not cause symptoms, and does not need to be treated. But be careful! Most of the time, high blood calcium is due to parathyroid disease , not FHH. The distinction matters, because the treatment is very different do nothing for FHH, surgery for parathyroid disease.
Most of the time, when we see someone who is diagnosed with FHH, he or she actually has a parathyroid tumor and needs an operation. FHH is very rare.
If you have high calcium levels, the odds are that you have a parathyroid tumor, and not FHH. People with FHH have high calcium levels their entire lives - it is normal for them, and does not need to be treated. FHH does not require treatment, and cannot be helped by parathyroid surgery. If your doctor has never mentioned FHH, then you do not need to read this page.
We see thousands of patients every year with high blood calcium, and we see a real case of FHH about once or twice year. If your calcium is high, and your PTH is above 35, the overwhelming odds are that you have a parathyroid tumor and your doctor is wrong - you do not have FHH.
This is important because if you have a parathyroid tumor you need an operation to remove it; if you have FHH, then avoid surgeons - an operation will not help you.
What are the symptoms of FHH? In general, FHH does not cause symptoms. People with FHH will always have high calcium levels, because their "normal" is high. Why do we care about FHH? The problem is that parathyroid disease can be mistaken for FHH. Most people with high calcium in the blood have a disease called primary hyperparathyroidism which is caused by a tumor of one of the parathyroid glands. We do not treat FHH, but primary hyperparathyroidism must be treated.
Unlike FHH, parathyroid disease can be devastating if left untreated. See our page on the symptoms of hyperparathyroidism. It is very important to separate out those people who have hyperparathyroidism and need an operation to feel better and to preserve their health, from those with FHH who need no treatment. For those with primary hyperparathyroidism, removing the parathyroid tumor that is causing the disease will cure the disease forever.
You will feel better and live longer. They have primary hyperparathyroidism. Because FHH is a genetic disease, the definitive way to diagnose it is with genetic testing discussed below. But some doctors try to diagnose it with urine calcium results.
This is the logic used: FHH produces high blood calcium and low urine calcium. Parathyroid disease produces high blood calcium and often but not always high urine calcium. Thus, some doctors believe that anyone with a high blood calcium and a low urine calcium must have FHH.
What is low? But the problem is that low urine calcium can also be seen in primary hyperparathyroidism. And because primary hyperparathyroidism is so much more common than FHH, if you have a high blood calcium and a low urine calcium, the odds are that you have primary hyperparathyroidism - not FHH.
Each dot on this graph represents a patient with high blood calcium. They all had primary hyperparathyroidism which is not in doubt because they had an operation where a parathyroid tumor was removed from their neck and after the operation they no longer had high blood calcium. The vertical axis shows the blood calcium level, showing that the majority but not all patients with primary hyperparathyroidism have blood calcium levels above The horizontal axis shows the amount of calcium in the urine of these 10, patients always measured over a 24 hour period.
The first thing that you will notice is that the 10, dots are completely random; they flow consistently from very low urine calcium levels to very high urine calcium levels. The second thing you see is that patients with parathyroid tumors can have very low urine calcium levels, medium normal urine calcium levels, or very high urine calcium levels. The third thing that you can see is that patients with parathyroid tumors who have very high blood calcium levels are NOT more prone to have high urine calcium levels patients with higher blood calcium levels do not have a higher propensity to have high urine calcium levels.
And finally, notice that we colored the dots red and blue, with red dots representing patients with primary hyperparathyroidism due to a parathyroid tumor in their neck who had calcium kidney stones , while the blue dots represent those patients with a parathyroid tumor but they do not have kidney stones. You can easily see that patients with parathyroid tumors can have kidney stones regardless of their blood calcium levels, and regardless of their urine calcium levels.
Said differently, you cannot predict which patients with primary hyperparathyroidism will get kidney stones based upon how high their blood calcium levels are or how high their hour urine calcium levels are. This is the same graph but we removed all the patients who had a hour urine calcium level of less than mg.
If the decades-old teachings were right and the level of was accurate in determining who had FHH and who had primary hyperparathyroidism then the graph would look like this. Of course this is absurd. The number is simply arbitrary because it is a nice round number, but the real world is not this simple.
They fall with a nice grouping from way down around 20 to way up to as seen in the first graph. The problem is the arbitrary number of it is simply dumb. You can learn more about parathyroid problems and interact with the graphs on this page on your iPad or Android device.
If you are reading this far on this page, then you may want to consider the CalciumPro app. Some of them had doctors who knew they had a parathyroid problem even though their hour urine was less than Many of them were told that they had FHH and that they should not have a parathyroid operation because they did not have a parathyroid tumor - simply because their hour urine calcium was less than The patients either sought the advice of a different endocrinologist, or they and their primary care doctor figured it out for themselves and underwent surgery.
Another important point that is made clear by the third graph is that there are lots of patients here that have kidney stones. As you will recall from the blue symptom table at the top of this page, patients with FHH do not get kidney stones, but patients with primary hyperparathyroidism can get stones.
You simply cannot differentiate between FHH and primary hyperparathyroidism based upon the amount of calcium in the urine. The next graph shows the hour urine calcium results for the same 10, patients with primary hyperparathyroidism. This time we present the data in a bar graph so you can see how often patients with a parathyroid tumor actually have a hour urine test with a result less than It happens 4. Genetic Testing for FHH OK, so now we all understand that almost all people who have high blood calcium will have a parathyroid tumor in their neck and this high calcium is not normal for them.
They have not had high calcium their entire life The parathyroid tumor makes too much parathyroid hormone which in turn takes calcium out of the bones and puts it into the blood. The high blood calcium in these folks came from their bones! These people get symptoms, they get sick, they get bad osteoporosis, they get kidney stones, they get high blood pressure, they get all sorts of bad things happening because of the high calcium and PTH in their blood.
In contrast, a very small minority of people with high calcium in their blood extremely rare will have FHH. This means it is normal for them to have this slightly higher blood calcium. They just have a higher "normal" calcium level in the blood. And yes we can. There are several companies now that can do this test for you. Two things to remember, 1 it is not cheap, and 2 it is not always correct either! See, even these genetic tests are not always correct because they have "control" DNA in their database that came from people with primary hyperparathyroidism but were misdiagnosed as FHH because of a urine calcium level below !
How crazy is that?! FHH is characterized by hypercalcemia, hypocalciuria, hypermagnesemia, and normal to low levels of parathyroid hormone PTH. To date over different alterations in the CASR gene have been described. Many of these cause diseases of abnormal serum calcium regulation. This leads to either familial hypocalciuric hypercalcemia FHH or neonatal severe primary hyperparathyroidism NSPHT , depending on the severity of the functional impairment.
Symptoms appear in infancy and include extreme hypercalcemia, failure to thrive, hypotonia, skeletal demineralization, and severe parathyroid hyperplasia. Treatment may require parathyroidectomy in these very young infants.
Serum calcium levels are mildly-to-moderately elevated. Parathyroid hormone PTH levels are within the normal range, phosphate is normal, and urinary calcium excretion is low for the degree of hypercalcemia.
In contrast to patients with primary hyperparathyroidism, the majority of FHH patients do not seem to suffer any adverse long-term problems from their high blood calcium hypercalcemia.
Identification of a heterozygous inactivating CASR mutation confirms this diagnosis, while identification of novel alteration s increases the likelihood of a FHH diagnosis, but does not confirm it until family studies or functional studies support the diagnosis. Absence of any mutations or the presence of polymorphism s that are known to be functionally neutral makes the diagnosis very unlikely. These patients can be difficult or impossible to distinguish from individuals with primary hyperparathyroidism PTH.
FHH vs Primary Hyperparathyroidism: The Bottom Line Bottom line is this: If your blood calcium is high, the odds are that you have a parathyroid tumor that is causing primary hyperparathyroidism. Genetic testing is used to diagnose FHH - urine calcium should never be used for diagnosis.
Most of the time, if you have FHH, then other members of your family will have it as well. If your doctor says you have FHH based only upon your urine calcium level, then demand a genetic test. The diagnosis of FHH should never be made without a genetic test. Get the Calcium-Pro parathyroid analysis app developed by our experts.
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Familial Hypocalciuric Hypercalcemia
Pathogenesis[ edit ] Most cases of FHH are associated with loss of function mutations in the calcium-sensing receptor CaSR gene,  expressed in parathyroid and kidney tissue. As a result, inhibition of parathyroid hormone release does not occur until higher serum calcium levels are attained, creating a new equilibrium. This is the opposite of what happens with the CaSR sensitizer, cinacalcet. Functionally, parathyroid hormone PTH increases calcium resorption from the bone and increases phosphate excretion from the kidney which increases serum calcium and decreases serum phosphate. Individuals with FHH, however, typically have normal PTH levels, as normal calcium homeostasis is maintained, albeit at a higher equilibrium set point. As a consequence, these individuals are not at increased risk of the complications of hyperparathyroidism. Another form has been associated with chromosome 3q.
Familial hypocalciuric hypercalcemia
FHH - Familial Hypocalciuric Hypercalcemia
Familial hypocalciuric hypercalcemia and related disorders.