Parathyroid surgery aims to address an abnormality in the production of parathyroid hormone (PTH).
The parathyroid glands are located in the neck, near the thyroid gland, hence the term para (beside) thyroid. They produce parathyroid hormone, which regulates calcium levels in the blood by its effect on bone, the gut and the kidney.
Posterior view of the thyroid/parathyroids
When calcium levels are too low, the body responds by increasing production of parathyroid hormone. This increase in parathyroid hormone causes more calcium to be taken from the bone and more calcium to be reabsorbed by the intestines and kidney. When the calcium level returns to normal, parathyroid hormone production slows down.
There are three types of hyperparathyroidism.
Primary hyperparathyroidism is caused by enlargement/overactivity of one or more of the parathyroid glands. This leads to too much parathyroid hormone, which raises the level of calcium in the blood. The long term consequences of all hyperparathyroidism include osteoporosis, kidney stones, pancreatitis and psychological effects.
Parathyroid adenoma 3450mg (normal size 30-50mg)
Secondary hyperparathyroidism is when the body produces extra parathyroid hormone because the calcium levels are too low, or the body's ability to correctly regulate calcium is impaired. This is seen when activated vitamin D levels are low or when calcium is not absorbed from the intestines. Correcting the calcium level and the underlying problem will bring the parathyroid levels in the normal range. The most common cause of secondary hyperparathyroidism is kidney failure. This impacts the activation of Vit D and hence the proper absorption and excretion of calcium. Inadequate kidney perfusion also impacts normal calcium regulation. Secondary hyperparathyroidism typically effects all four parathyroid glands. If long term kidney failure is corrected, eg by transplant, the severity of secondary hyperparathyroidism can be altered.
If the parathyroid glands continue to produce too much parathyroid hormone even though the calcium level is back to normal following, for example, kidney transplantation, the condition is called tertiary hyperthyroidism.
Once the diagnosis of hyperparathyroidism is made on blood and urine tests, ultrasound and nuclear medicine scans are commonly employed to determine whether a single gland, or multiple glands are to blame. When a single gland is the cause, more than 99% are due to benign adenomata, and the remainder are due to a malignancy of the parthyroid gland. Occasionally, two glands can undergo adenomatous change. When no single gland is the cause, parathyroid hyperplasia is the cause. This is when all four glands are abnormal and overactive.
Ultrasound will also allow the surgeon to assess both parathyroids and the thyroid gland. A percentage of patients with hyperparathyroidism have thyroid problems, including cancer. Given the proximity of the thyroid and parathyroid glands, it is normal for patients with both thyroid and parathyroid disease to have them treated at a single operation.
Parathyroid surgery needs to be tailored to the cause. If a single gland is the cause, ie a parathyroid adenoma, the condition can be cured by the removal of this abnormal gland. This can be achieved in one of two ways. The most traditonal approach to hyperparathyroidism is to undertake a four gland exploration and for the abnormal gland to be removed.
If only 1 gland is identified by ultrasound and nuclear medicine scans, a minimally invasive parathyroidectomy is possible, requiring a smaller incision and shorter operating time.
Minimally invasive parathyroidectomy incision
Parathyroid surgery needs to occur in hospital, and in almost every case, under general anaesthetic. Patients with primary hyperparathyroidism who have a minimially invasive parathyroidectomy can usually go home from hospital on the day of surgery. This short duration of admission does not apply to all patients, and those with secondary hyperparathyroidism often require up to 10 days stay in hospital.
The risks of parathyroid surgery include
- bleeding and infection as in any operation
- injury to the recurrent laryngeal nerve causing a change in the voice
- recurrent hyperparathyroidism due to the persistence/emergence of abnormal parathyroid tissue
These risks apply to any parathyroid operation, but will vary in incidence with the type of hyperparathyroidism and hence the operation that is required.