The parathyroid glands are small, pea-sized structures located in the neck, typically positioned behind the butterfly-shaped thyroid gland. Most individuals have four of these glands, which play a role in regulating calcium levels in the bloodstream. They achieve this by producing parathyroid hormone (PTH), which helps maintain a precise balance of calcium, a mineral for nerve function, muscle contraction, and bone health. Tumors can sometimes develop in these glands, and understanding their occurrence involves examining how common these growths are.
What Parathyroid Tumors Are
Parathyroid tumors are abnormal growths of cells within the parathyroid glands. These growths can disrupt the glands’ ability to regulate calcium, often leading to an overproduction of parathyroid hormone. The majority of these tumors are benign, meaning they are non-cancerous and do not spread to other parts of the body.
The most frequent type of parathyroid tumor is a parathyroid adenoma, a single growth that causes one gland to become overactive. Another form is parathyroid hyperplasia, where all four parathyroid glands become enlarged and overactive. Rarely, a parathyroid tumor can be malignant, known as parathyroid carcinoma. This is a cancerous growth that can invade surrounding tissues and spread to other areas of the body.
How Often They Occur
Primary hyperparathyroidism, often caused by parathyroid tumors, is a common endocrine disorder. The occurrence of these tumors can be described by prevalence and incidence. Prevalence refers to the total number of people living with the condition at a given time, while incidence reflects the number of new cases diagnosed over a specific period.
Overall prevalence estimates for primary hyperparathyroidism in the adult population range from approximately 0.2% to 1.3%. Incidence rates of new cases vary, falling within a range of 4 to 18 cases per 10,000 people per year.
Obtaining exact numbers can be challenging because many individuals with parathyroid tumors, particularly in their early stages, may not experience noticeable symptoms. The widespread use of routine blood tests, which often include calcium level checks, has led to more frequent incidental diagnoses of these tumors. This has contributed to an apparent increase in reported cases over time.
Who Is Most Affected
Certain demographic factors and medical conditions are associated with an increased likelihood of developing parathyroid tumors. Age is a factor, with the incidence of these tumors rising with advancing age. The highest rates are observed in middle-aged to older adults.
Gender also plays a role, as parathyroid tumors are more frequently diagnosed in women than in men. Women are approximately two to three times more likely to develop these growths. Genetic predispositions account for about 10% of cases, with certain inherited syndromes increasing the risk. Prior exposure to radiation, especially to the neck area, has also been identified as a contributing factor.
Benign Versus Malignant Tumors
It is important to distinguish between benign and malignant forms of parathyroid tumors. Most parathyroid tumors are benign. Parathyroid adenomas account for 80% to 90% of all cases of primary hyperparathyroidism. Parathyroid hyperplasia makes up another 5% to 15% of cases.
Parathyroid carcinoma, the cancerous form of these tumors, is very rare. It accounts for less than 1% of all parathyroid tumors. This type of cancer is one of the rarest forms of cancer overall. The difference in commonality between benign and malignant parathyroid tumors shows that discussions about parathyroid tumors overwhelmingly refer to the more prevalent, non-cancerous varieties.