The parathyroid glands, small structures located in the neck, play a significant role in regulating the body’s calcium balance. A parathyroid adenoma is a non-cancerous growth that can develop on one of these glands. This growth often leads to an overproduction of parathyroid hormone, disrupting the body’s normal calcium levels.
What Parathyroid Adenomas Are
Most individuals possess four pea-sized parathyroid glands, typically situated behind the thyroid gland in the neck. These glands produce parathyroid hormone (PTH), which is a chemical messenger responsible for maintaining stable levels of calcium and phosphorus in the bloodstream. PTH works by influencing how much calcium is released from bones, absorbed from food in the intestines, and reabsorbed by the kidneys.
A parathyroid adenoma is a benign tumor that forms on one of these glands. This tumor causes the affected gland to produce excessive PTH, leading to primary hyperparathyroidism and elevated blood calcium (hypercalcemia). In the majority of cases, a single adenoma is responsible for primary hyperparathyroidism.
Average Size and Clinical Significance
Normal parathyroid glands are quite small, often compared to a grain of rice or an apple seed, and weigh less than 0.5 grams. In contrast, a parathyroid adenoma is an enlarged gland. Studies indicate that the median maximum dimension of these adenomas is around 15 millimeters (1.5 cm), with weights averaging about 500 milligrams (0.5 grams). Some adenomas can grow larger, described as reaching the size of a peanut, an olive, or even a grape, particularly if they have been present for an extended period.
The size of a parathyroid adenoma often correlates with the amount of parathyroid hormone it produces. Larger adenomas typically secrete higher levels of PTH, which leads to more significant elevations in blood calcium. This increased hormonal activity can contribute to various symptoms, including bone pain, kidney stones, and fatigue. Patients with very large adenomas, sometimes weighing over 3.5 grams, may not always experience more severe symptoms and can even be asymptomatic.
How Parathyroid Adenomas Are Identified
Parathyroid adenomas are frequently discovered incidentally during routine blood tests that reveal higher-than-normal calcium levels. Once elevated calcium is noted, the diagnosis of primary hyperparathyroidism is confirmed by measuring parathyroid hormone (PTH) levels, which will also be elevated. This biochemical confirmation is a step before proceeding to imaging studies.
After biochemical diagnosis, imaging techniques are employed to pinpoint the location of the adenoma and assess its size. Ultrasound is often a first-line imaging modality, capable of visualizing adenomas larger than 1 centimeter. Technetium-99m sestamibi scintigraphy, often combined with SPECT, is a highly sensitive nuclear medicine scan that helps identify overactive parathyroid tissue. 4D computed tomography (CT) scans also provide detailed anatomical information, useful for locating adenomas that are difficult to find or are in unusual (ectopic) locations. These imaging methods collectively help precisely locate the affected gland and measure its dimensions, guiding subsequent treatment decisions.
Management and Treatment Options
The most effective treatment for a parathyroid adenoma causing primary hyperparathyroidism is surgical removal, known as parathyroidectomy. This surgery has a high success rate, curing over 95% of patients. When the adenoma has been accurately located pre-operatively, a minimally invasive surgical approach can often be used, resulting in smaller incisions and shorter recovery times.
Surgery is generally recommended for individuals experiencing symptoms, those under 50 years old, or patients with elevated blood calcium, bone loss, or kidney complications like kidney stones. In some mild cases, where symptoms are absent or minimal, calcium levels are stable, and there is no apparent organ damage, watchful waiting may be considered. While medications can help manage symptoms or protect bones, they do not cure the underlying issue of PTH overproduction. Treatment decisions are based on a thorough evaluation of the patient’s overall health, symptoms, and the potential impact of high calcium levels, not solely on adenoma size.