Low Serum Calcium
Low Serum Calcium
One of the risks of a total thyroidectomy is the possibility of low serum calcium after the operation, either on a temporary or permanent basis.
Let me explain how this might occur.
There are four small glands, a little less than pea-size, that live next to the thyroid gland that are called “parathyroid glands’. They get their name from their location and have absolutely nothing to do with thyroid gland function. These glands make a hormone called PTH, or parathyroid hormone, a hormone whose job it is to keep the level of calcium in the blood normal. It does this by many mechanisms, helping you absorb calcium from your diet, managing the calcium in bones, and so on. If one were to lose all four of his or her parathyroid glands, the serum calcium would take a serious drop and replacement calcium and Vitamin D would probably have to be taken for life.
When performing thyroid surgery, it is prudent to look for and preserve these glands immediately after locating and preserving the recurrent laryngeal nerve, discussed elsewhere. On the surface this seems like a simple thing to do, but it isn’t always for several reasons. First, not everyone has 4 parathyroid glands, some have 5 or more and others may have only three or less. Next, their location in the neck can be extremely variable, in fact, one or more may not actually be in the neck at all, but rather in the upper chest or other atypical location. Finally, they are sometimes rather nicely camouflaged sitting in the soft fatty tissues of the neck. It can often require an experienced thyroid surgeon to discern the very subtle color differences between parathyroid tissue and normal adjacent fat and soft tissue.
If one were to lose all four glands, or if all four glands died from lack of blood supply secondary to the trauma of surgery, that patient would in all likelihood have permanent low calcium after surgery. This, of course, assumes the patient has the normal number of parathyroid glands. It is possible to lose the function of one or two parathyroids and have no calcium difficulties whatsoever, because the remaining two glands can almost always take up the slack and maintain normal calcium levels. This is why we virtually never see even temporary low calcium after only a partial thyroidectomy since the glands on the unoperated side are left unmolested. Again, this always assumes the patient started out with 4 parathyroid glands, and there is never any guarantee or that.
It is for these two reasons, variation in number and variation in anatomy, two variables over which the surgeon has no control, that I always spend a little extra time with my patients preoperatively explaining all potential postoperative calcium scenarios.
Temporary low calcium levels can be seen after thyroidectomy simply because the parathyroid glands became bruised or swollen after surgery, thus making it difficult for them to produce normal amounts of parathyroid hormone. These patients may have a temporary low calcium that requires minimal or no calcium replacement and in time the parathyroid glands function well once again.
We perform a great number of total thyroidectomies for patients suffering with Graves’ Disease, patients who don’t want the risks of medical treatment or the exposure to radiation that comes with radioactive Iodine treatment. Because all of the gland is always removed there is the risk of low calcium after surgery. However, these patients have still another potential cause for temporary low calcium after surgery and that is what’s called “Hungry Bone Syndrome”. These patients have lost a great deal of calcium from their bones as a result of their disease. Once the disease is cured, the bones voraciously try to absorb calcium from the bloodstream, thus contributing to the possibility of temporary low serum calcium levels postoperatively.
The treatment for low calcium after total thyroidectomy is to supplement the diet with calcium and perhaps Vitamin D until the situation corrects itself. There are a number of calcium supplements in various forms such as pills, syrups, and liquids that perform the job quite nicely. Most instances of temporary low calcium resolve in as little as a few days to as long as a month or two. As long as sufficient living parathyroid tissue is left behind after surgery, the calcium levels should ultimately be just fine.
Below are two photos intended to give you a feel for what the parathyroid glands are and what they look like. As you can see, they are often found very close to the location of the recurrent laryngeal nerve.
