This article addresses whether hyperparathyroidism, a common endocrine disorder, is an autoimmune disease. It explores the causes and characteristics of both conditions.
Understanding Hyperparathyroidism
Hyperparathyroidism occurs when one or more parathyroid glands become overactive, producing excessive parathyroid hormone (PTH). These four tiny glands, located behind the thyroid in the neck, maintain precise levels of calcium and phosphorus in the blood. PTH influences bones, kidneys, and the small intestine to regulate these mineral levels. Too much PTH leads to elevated blood calcium, known as hypercalcemia.
High calcium can weaken bones, leading to osteoporosis and an increased risk of fractures. It can also contribute to kidney stones and impact kidney function. Other consequences of hypercalcemia include fatigue, muscle weakness, increased thirst, and digestive issues like constipation.
Understanding Autoimmune Diseases
Autoimmune diseases occur when the body’s immune system mistakenly attacks its own healthy tissues or organs. This leads to an immune response where autoantibodies and specialized T-cells target self-antigens.
The immune system’s attack can result in inflammation and damage to various parts of the body, depending on the specific autoimmune disease. While the exact triggers are not fully understood, factors such as genetics, infections, and environmental influences can play a role. There are over 80 recognized autoimmune conditions, and symptoms can vary widely, often fluctuating between periods of activity and remission.
Hyperparathyroidism: Not an Autoimmune Condition
Primary hyperparathyroidism is generally not classified as an autoimmune disease. The most common cause (about 85% of cases) is a single, non-cancerous growth (adenoma) on one of the parathyroid glands. This adenoma causes the affected gland to become overactive and autonomously produce excessive PTH, regardless of the body’s calcium needs.
This overproduction stems from localized cellular changes within the gland, not a systemic immune attack. Less common causes, such as the enlargement of multiple parathyroid glands (hyperplasia) or, in rare cases, parathyroid carcinoma, also do not involve an autoimmune mechanism.
Primary Causes of Hyperparathyroidism
Hyperparathyroidism is categorized into distinct types based on its underlying causes. Primary hyperparathyroidism originates from a problem within the parathyroid glands themselves. A benign tumor (adenoma) on one gland is the most frequent cause, leading to uncontrolled PTH secretion. Less commonly, enlargement of all four glands (hyperplasia) or, in very rare instances, parathyroid cancer can cause this primary form.
Secondary hyperparathyroidism develops as a physiological response to another condition that causes persistently low calcium levels in the blood. Chronic kidney disease is the most common cause, as impaired kidneys cannot properly activate vitamin D for calcium absorption. Severe vitamin D deficiency from other sources can also lead to this type. The parathyroid glands increase PTH to raise low blood calcium, overworking due to an external problem.
Tertiary hyperparathyroidism can occur when long-standing secondary hyperparathyroidism progresses. Overstimulated for an extended period, the parathyroid glands become autonomous, overproducing PTH even after the initial cause of low calcium is addressed. They lose their ability to regulate PTH production.
Autoimmune Issues and the Parathyroid Glands
While hyperparathyroidism is generally not an autoimmune condition, autoimmune processes can affect the parathyroid glands, leading to hypoparathyroidism. Autoimmune hypoparathyroidism occurs when the immune system directly attacks and damages the parathyroid glands. This destruction results in insufficient PTH production and low blood calcium (hypocalcemia).
This type of parathyroid dysfunction can manifest as an isolated condition where only the parathyroid glands are targeted. It can also be part of broader autoimmune syndromes, such as Autoimmune Polyendocrine Syndrome Type 1 (APS-1), where the immune system attacks multiple endocrine glands.
Autoimmune attacks on the parathyroid glands cause them to become underactive, leading to low PTH and low calcium. Hyperparathyroidism, in contrast, involves the overproduction of PTH and high calcium levels, usually due to a non-autoimmune growth or external stressor. While some studies explore associations between primary hyperparathyroidism and other autoimmune conditions, this does not classify hyperparathyroidism itself as autoimmune.