Your Parathyroid:
Parathyroid glands are small glands
of the endocrine system which are normally about the size and shape of a grain
of rice. The sole purpose of the parathyroid glands is to regulate the calcium
level in our bodies within a very narrow range so that the nervous and muscular
systems can function properly. Although they are neighbors and both part of the
endocrine system, the thyroid and parathyroid glands are otherwise unrelated.
The single major disease of the parathyroid glands is overactivity of one or
more of the parathyroid glands which make too much parathyroid hormone causing
a potentially serious calcium imbalance. This is called hyperparathyroidism.
Parathyroid Function:
The sole purpose of the parathyroid
glands is to control calcium within the blood in a very tight range between 8.5
and 10.5. In doing so, parathyroid glands also control how much calcium is in
the bones, and therefore, how strong and dense the bones are. Although the parathyroid
glands are intimately related to the thyroid gland anatomically, they have no
related function. The thyroid gland regulates the body’s metabolism and has no
effect on calcium levels while parathyroid glands regulate calcium levels and
have no effect on metabolism. Calcium is the primary element which causes
muscles to contract. Calcium levels are also very important to the normal
conduction of electrical currents along nerves. Knowing these two major
functions of calcium helps explain why people can get a tingling sensation in
their fingers or cramps in the muscles of their hands when calcium levels drop
below 8.5(like immediately after a successful parathyroid operation). Likewise,
too high a calcium level can cause a person to feel run down, cause them to
sleep poorly, make them more irritable than usual, and even cause a decrease in
memory.
Normal Parathyroid Activity:
Although the four parathyroid
glands are quite small, they are very vascular. This suits them well since they
are required to monitor the calcium level in the blood 24 hours a day. As the
blood filters through the parathyroid glands, they detect the amount of calcium
present in the blood and react by making more or less parathyroid hormone (PTH).When
the calcium level in the blood is too low, the cells of the parathyroid glands
sense it and make more parathyroid hormone. Once the parathyroid hormone is
released into the blood, it circulates to act in a number of places to increase
the amount of calcium in the blood (like removing calcium from bones). When the
calcium level in the blood is too high, the cells of the parathyroids make less
parathyroid hormone, thereby, allowing calcium levels to decrease. This
feed-back mechanism runs constantly, thereby maintaining calcium in a very narrow
“normal” range.
How Parathyroid Hormone Increases Blood Calcium:
Like all endocrine glands,
parathyroids make a hormone (a small protein capable of causing distant cells
in the body to react in a specific manner). Parathyroid hormone (PTH) has a very
powerful influence on the cells of the bones which causes them to release their
calcium into the blood stream. Calcium is the main structural component of
bones which give them their rigidity. Under the presence of parathyroid hormone,
bones will give up their calcium in an attempt to increase the blood level of
calcium. Under normal conditions, this process is very highly tuned and the
amount of calcium in our bones remains at a normal high level. Under the
presence of too much parathyroid hormone, however, the bones will continue to
release their calcium into the blood at a rate which is too high resulting in
bones which have too little calcium. This condition is called osteopenia and
osteoporosis and is illustrated in the bone segment which has large
“pores” and less bone mass. When
bones are exposed to high levels of parathyroid hormone for several years they
become brittle and much more prone to fractures. Another way in which
parathyroid hormone acts is to increase blood levels of calcium by increasing
the absorption of calcium from the intestines.
Hyperparathyroidism:
The primary disease of parathyroid
glands is overactivity-- too much parathyroid hormone is produced. This is
called hyperparathyroidism. Under this condition one or more of the parathyroid
glands behaves inappropriately by making excess hormone regardless of the level
of calcium. In other words, the parathyroid glands continue to make large
amounts of parathyroid hormone even when the calcium level is normal and they
should not be making hormone at all. Remember as you read these pages, it’s a
hormone problem, not a cancer problem.
What Causes Excess Hormone Production:
The most common cause of excess
hormone production is the development of a benign tumor in one of the
parathyroid glands. This enlargement of one parathyroid gland is called a
parathyroid adenoma which accounts for 96% of all patients with primary
hyperparathyroidism. This situation is illustrated here: one of the parathyroid
glands has developed a tumor which is secreting all the hormone and the other
three glands are small and responding appropriately to the high calcium by
becoming dormant
.
This out of control parathyroid
gland is essentially never cancerous (less than one in 2500); however, it
slowly causes damage to the body because it induces an abnormally high level of
calcium in the blood which can slowly destroy a number of tissues.
Approximately 3-4% of all patients
with primary hyperparathyroidism will have an enlargement of all four
parathyroid glands, a tem called parathyroid hyperplasia. In this instance, all
of the parathyroid glands become enlarged and produce too much parathyroid
hormone. This is a much less common scenario but the end results on the tissues
of the body are identical.( other causes of four gland enlargement are: long
term Lithium therapy, radioactive Iodine therapy for thyroid cancer, kidney
failure, familial forms, and Multiple Endocrine Neoplasia Syndrome). An even
rarer situation occurs in less than 1% of the people who have two parathyroid
adenomas while having two normal glands. This is very uncommon situation and
can make the diagnosis and treatment of this disease a bit trick
Symptoms of Hyperparathyroidism:
Since hyperparathyroidism was first
described in 1925, the symptoms have become known as “moans, groans, stones,
and bones.” Although most people with primary hyperparathyroidism claim to feel
well when the diagnosis is made, the majority of these will actually say the
feel better after the problem has been cured. Known complications:
Sever
osteoporosis and osteopenia
Bone
fractures
Kidney
stones
Peptic
ulcers
Pancreatitis
Nervous
system complaints (unable to sleep, confusion, forgetfulness)
The incidence of these problems
depends primarily on the duration of the disease and its severity. Everybody
will lose bone density, which is progressive. Pancreatitis and ulcers are much
more rare. Even though the majority of patients claim they feel fine when this
disease is diagnosed, all most 80% of them claim to feel better (sleep etc.)
three months after the problem has been fixed. Do not elect to undergo surgery
based upon how your feel. Remember, the typical patient has had this disease
for several years before it was ever found, because it does its bad things so
silently. The good news is that it can be cured with routine operation which
caries a success rate of about 95%.
Diagnosis of Hyperparathyroidism:
Since parathyroid glands are part
of the endocrine system, we can detect disease in these glands by measuring the
appropriateness of their hormone. Under normal conditions, a normal calcium
level will be associated with a normal parathyroid hormone level. Also under
normal conditions, a low serum calcium level will be associated with a high
parathyroid hormone level; and a high calcium level will be associated with a
low parathyroid hormone level. These are all appropriate ways in which a
parathyroid gland will react to calcium which is circulating in the blood. In
hyperparathyroidism the parathyroid glands will be making an inappropriately
large amount of parathyroid hormone in the face of an elevated serum calcium.
This is straightforward and simple to measure. Another way to confirm this
diagnosis is by measuring the amount of calcium in the urine over a 24-hour
period of time. If the kidneys are functioning normally they will filter much
of this calcium in an attempt to rid the body of calcium leading to an abnormally
large amount of calcium in the urine. Measuring calcium in the urine, however,
is an indirect measure of parathyroid activity and is only accurate in about
25-40% of the time. The most accurate
and definitive way to diagnose primary hyperparathyroidism is by showing an
elevated parathyroid hormone level in the face of an elevated calcium.
Once the diagnosis is made your
doctor may try to determine the location of the abnormal gland. CT, MRI and
ultrasound are of limited value. The Sestamibi Scan seems to be the best test
to try and localize the adenoma prior to surgery. The test is done by injected
a small radioactive protein into a vein in the patient. This radioactive
protein is absorbed by the overactive parathyroid gland and hopefully will show
up on a special scan of the neck. This test may or may not be able to localize
the parathyroid adenoma.
Treatment:
Surgery is the way to cure parathyroid disease.
There are no medications or pills that work to cure parathyroid disease. The
parathyroid tumor must be removed by a surgeon. As soon as the parathyroid
tumor has been removed, you are cured. Since 1925, the standard treatment for
parathyroid disease (primary hyperparathyroidism) has been to surgically remove
the parathyroid gland (or glands). Again, the concept is really quite simple:
Find which parathyroid gland has become a tumor and is making too much
parathyroid hormone and take it out—leaving the other normal parathyroids
alone. The normal parathyroid glands will take over and you will be cured. You
don’t need all four parathyroid glands. The standard parathyroid operation is
performed by putting the patient to sleep under general anesthesia. An incision
is made in the neck, the muscles of the neck retracted sideways and the thyroid
gland is mobilized to allow the surgeon to identify the four parathyroid glands
which reside moderately deep in the neck behind the thyroid. Patients usually stay in the hospital
overnight to be sure the calcium level does not drop too low. During the
surgery the surgeon will try to identify all four parathyroid glands and remove
whichever one(s) is enlarged. Approximately 95% of the time this is one large
parathyroid gland (an adenoma which is a benign parathyroid tumor) and three
normal parathyroid glands. In this situation the one large gland (parathyroid
adenoma) would be removed leaving the three normal ones to function in a normal
fashion indefinitely. If the surgeon found all four parathyroid glands to be
enlarged (found in only 3-4% of patients and called: parathyroid hyperplasia),
he would typically take out 3-1/2 of these glands leaving some parathyroid
tissue behind to function normally in the future (you only need ½ of a
parathyroid gland to function normally).
The principle of parathyroid surgery is simple but the
parathyroid glands can be hard to find. There are four parathyroid glands and
they can be located all over the neck. The key to successful operation is for
the surgeon to find the bad parathyroid gland. Parathyroid glands have the most
un-predictable anatomy in the human body. Parathyroid glands are typically
found on the back side of the thyroid gland. In fact, about 85% of parathyroid
glands are found here. The picture shows the back side of the thyroid gland,
showing that the four parathyroid glands are closely associated with the back
of the thyroid.
However, because of how parathyroid glands are formed (when
we are in our mother’s womb), they can be anywhere in the neck from just below
the jaw—all the way down into the chest and nest to the heart. They can even be
inside the thyroid gland. The picture below shows the location of the thyroid
gland in the patient’s neck. The black dots outline the position that the left
parathyroid glands can be found.
You
can see that 15% of parathyroid glands are not found next to the thyroid, thus
these little guys can be very hard to find! Remember, parathyroid glands are
only the size of a grain of rice (half a pea) when the are normal and get to be
about the size of a grape when they develop into a tumor (parathyroid adenoma).
The important thing to remember is that this is a benign
tumor and surgery with removal of the tumor will cure 95% of all patients.
