What are the parathyroid glands?
They are small glandular structures, located at the upper and lower ends of each side of the thyroid. There are usually four of them, about the size of a lentil, brownish in color, and they are usually surrounded by fat.
Their mission is to secrete a hormone called parathyroid hormone (PTH), which is responsible for maintaining calcium levels (increasing calcium levels in the blood and decreasing its deposition in the bone). If calcium is elevated, there is usually a parathyroid problem.
For what reasons may its removal be required?
The most common cause of parathyroid gland surgery is elevated PTH secretion, which causes elevated blood calcium, known as primary hyperparathyroidism. This elevation of calcium causes a decrease in bone mass (osteoporosis), renal colic (renal lithiasis), fatigue, depression, among other symptoms.
The most frequent cause of hyperparathyroidism is the presence of a parathyroid adenoma. An adenoma is the result of the increase in size of one of the parathyroid glands, which autonomously starts to function, without responding to the usual control mechanisms. This causes increased levels of calcium in the blood, which may not cause any symptoms and may be a casual finding in a routine analysis. Other times it causes symptoms such as bone pain, kidney cramps, tiredness, depression.
Another type of hyperparathyroidism, known as secondary, appears in patients with chronic renal pathology, but is much less frequent. It is characterized by an increase in the size of the four parathyroid glands.
When there is a suspicion of hyperparathyroidism, parathyroid exploration is performed to try to identify which gland or glands are affected. In parathyroid surgery there is a classic aphorism that “the best way to find a parathyroid is a surgeon who knows how to find it” (Doppman JL, 1986). And this is true in most cases, although today the use of imaging tests and nuclear medicine (Figure 1) allows us to know the location of the affected gland with a high degree of certainty. But despite these localization techniques, as with thyroid gland surgery, it must be performed by expert surgeons.
The presence of parathyroid carcinomas is very rare, affecting approximately 1% of all cases of hyperparathyroidism. In these cases it is necessary to perform a wider resection of the lesion, including the hemithyroid on the same side.
How is the procedure performed?
Parathyroid removal requires surgical exploration of the neck under general anesthesia. This exploration can be performed by open surgery or by minimally invasive video-assisted surgery (MIVAP). In either case it must be performed by surgeons who are experts in these techniques. The reason is that the affected gland is identified 95% of the time (Figure 2). But sometimes its identification is not so simple, especially when the affected gland is an inferior one, or if there is a supernumerary gland. In these cases the gland may be located in the carotid sheath, behind the esophagus, in the fat surrounding the thymus, or even in the pericardium, requiring meticulous, extensive and delicate surgical exploration.
For the exploration, a small incision is made at the root of the neck and the muscles covering the thyroid are separated. Once the thyroid is identified, the capsule covering it is dissected and the middle thyroid vein is ligated, which allows us to tract the thyroid lobe to identify the recurrent nerve and the inferior thyroid artery. These two structures are the reference for finding the parathyroids in their usual position. If we know the location of the affected gland we will look for it in that location. If the presence of the affected gland is confirmed we proceed to perform a blood extraction to measure the PTH value. We remove the gland, taking care not to break it and not to injure the recurrent nerve (Figure 2), and perform a new blood draw to evaluate the PTH levels, 10 minutes after the extraction. While the PTH measurement is being taken, we proceed to the histological study of the removed gland, confirming that it is an anomalous parathyroid.
If the post-extraction PTH levels decrease by more than 50% with respect to the pre-extraction levels, it is considered that the removed gland was the problem and the intervention is considered to be finished. When this is not the case, or when we have not found the abnormal gland in the place we expected, it is necessary to explore all the glands until the one causing the hyperparathyroidism is found.
What is the postoperative period like?
In both open and minimally invasive surgery, the postoperative period is easy. Discharge is usually within 24 hours and does not require specific medication apart from an analgesic if necessary.
A determination of calcium in the blood should be done to confirm that the levels are within normal limits. Visualization of the vocal cords, both before and after is a scan that should always be performed.