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| CANTERBURY HEALTH LABORATORIES |
What are the parathyroid glands and what do they do?
What happens if the parathyroid glands become overactive?
Why does an overactive gland develop?
Is there anything I can do for myself?
What active treatment can be given?
Are there any other conditions I need to watch out for?
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The parathyroid glands are 4 tiny pieces of tissue, each about the size of a grain of rice, situated on either side of the thyroid gland in the neck (see picture). These glands are responsible for maintaining a normal level of calcium in the blood - without them the blood level of calcium would fall to very low levels (producing symptoms of painful muscle cramping, fatigue and other unpleasant effects). |
The parathyroid gland keeps the blood calcium level normal by secreting a hormone called parathyroid hormone (or PTH for short). This hormone then circulates in the blood stream and acts on the intestine and the kidney to increase the absorption of calcium back into the blood stream.
In normal health, if the calcium level were to fall (for instance, too little calcium in the diet), the parathyroid gland would increase its hormone output and more calcium would be absorbed from the food.
The opposite would occur if the calcium level were to rise. This way the body maintains a normal level of calcium - (usually around 2.2 to 2.6 mmol/L).
This condition of overactive parathyroid glands usually leads to a higher than normal blood level of parathyroid hormone and an increase in the blood calcium level.
Doctors refer to this condition as "primary hyperparathyroidism" - meaning that for some unknown reason the parathyroid gland has become "overactive". The condition is not rare; there would be about 60-100 people affected every year in the Christchurch area, though most of these people would feel entirely well and not know they had the condition.
Symptoms do occur, however, when the blood calcium level rises well above the normal range -for instance above 3.0 mmol/L. Then, thirst and increased volume of urine (often interrupting sleep as the bladder fills more rapidly at night), and other symptoms such as muscle fatigue and poor mental concentration can occur.
Very rarely the calcium level can become dangerously high, producing nausea, loss of appetite, vomiting and mental confusion. Should this happen, the patient would require urgent medical attention and treatment in hospital to correct the dehydration and return the calcium level to normal.
Another consequence of raised calcium levels in the blood is the possibility of kidney stones. These can develop with time, unbeknown to the patient, even at quite modest levels of increased blood calcium. For this reason, your doctor will usually do a screening test to be sure your kidneys are functioning normally and that you do not have any stones developing.
Only a small proportion (less than 1 in 10 people with an overactive parathyroid gland) actually develop kidney stones in New Zealand.
Finally, overactive parathyroid glands can weaken the bone structure over time. This occurs because high levels of PTH lead to loss of calcium from the skeleton, increasing the risk of brittle bones or fracture.
Usually this is not a serious problem but your doctor will often check that our bones are healthy by doing a test (a bone scan) that measures the bone density.
Usually we do not have an answer to this question. Occasionally the condition arises in several members of a family, or is passed down from affected parents but this is the exception.
In over 80% of cases, one of the 4 glands enlarges and becomes an adenoma (a small "growth" but not malignant). Because the gland is bigger (perhaps the size of a peanut it makes more PTH and eventually the calcium levels rises above normal. Because the enlargement is so small, pressure symptoms from the small lump do not occur.
Once the diagnosis is established, your doctor will talk to you about the pros and cons of active treatment (see below). There are several things you can do to prevent complications.
First it is wise to drink a reasonable quantity of fluid (water is best) - particularly in hot climates - and avoid dehydration. The risk of kidney stones is greater if the urine becomes too "strong" or concentrated.
Second, some drugs should be avoided - for instance Vitamin D or calcium pills should not be taken, unless specifically approved by your doctor. Some "fluid pills" can also worsen the problem, particularly "thiazide" diuretics such as Navidrex. You should check with your doctor and make sure that any pill you are given will not affect the calcium level.
Third, it is wise to have the blood calcium level checked each year, through your doctor, just in case it is rising more than expected. Usually the level is fairly stable from year to year but sudden increases can occur. If you feel unwell for no good reason, or develop any of the features mentioned above (thirst, increased urine formation, abnormal tiredness etc), you should have the blood level of calcium checked promptly.
Generally there is no restriction on your other activities or diet, and it is usually unnecessary to reduce the intake of milk or dairy products, provided your daily intake of these is not excessive.
A very effective treatment is surgical removal of the abnormal overactive parathyroid gland by an experienced parathyroid surgeon.
Usually only one of the 4 glands needs to be removed, the remaining glands providing a sufficient source of PTH to keep the calcium level normal once the small tumour is removed. Your doctor or surgeon will, of course, fully explain surgical details, or any risk, before the operation.
At present we do not have an effective medical treatment, but it is important to emphasise that the indications for surgery are somewhat ill defined.
Most authorities recommend surgery when there are prominent symptoms, when kidney stones are present, and or when the calcium level is rising above 3.0 mmol/L. In most other cases, a satisfactory alternative is to "wait and see", with calcium checks annually. At the present state of our knowledge, we do not think your health or life expectancy will be in any way impaired by taking this approach.
Increased blood pressure is often present in patients with raised calcium levels, but is not necessarily helped by correcting the calcium level.
Your doctor will want to check your blood pressure and kidney function at regular intervals but there is usually no concern if levels are under 3.0 mmol/L and there is no previous history of kidney disease.