Hyperparathyroidism describes a condition where the parathyroid glands become overactive, producing too much parathyroid hormone. This hormone imbalance affects various bodily functions, particularly mineral regulation. This article examines secondary hyperparathyroidism, a type where the glands’ overactivity responds to an underlying problem elsewhere in the body.
The Parathyroid Glands and Their Role
The parathyroid glands are typically four small, pea-sized glands located in the neck, usually behind the thyroid gland. Their primary function is producing parathyroid hormone (PTH), essential for maintaining stable levels of calcium and phosphate in the blood, crucial for proper nerve, muscle, and heart function. PTH works in several ways to increase blood calcium when levels are low. It stimulates calcium release from bones, signals kidneys to reabsorb more calcium and excrete phosphate, and facilitates vitamin D activation to enhance calcium absorption from food.
What Secondary Hyperparathyroidism Means
Secondary hyperparathyroidism (SHPT) occurs when the parathyroid glands become overactive and produce excess PTH in response to another condition, rather than a primary issue within the glands themselves. This compensatory mechanism is triggered by persistently low blood calcium or elevated blood phosphate levels. The parathyroid glands enlarge and work harder to normalize these mineral imbalances.
A common cause of SHPT is chronic kidney disease (CKD). Damaged kidneys struggle to excrete phosphate, leading to high blood phosphate, and cannot properly convert vitamin D, resulting in low calcium absorption. Both high phosphate and low calcium stimulate increased PTH production.
Severe vitamin D deficiency, often due to insufficient sunlight exposure or dietary intake, also leads to SHPT because inadequate vitamin D impairs calcium absorption, causing blood calcium to drop. Malabsorption syndromes, which hinder the body’s ability to absorb sufficient calcium or vitamin D from food, can similarly trigger this condition.
Impact on Your Health
Long-term, uncontrolled secondary hyperparathyroidism can lead to health complications as the continuous overactivity of the parathyroid glands affects other body systems. One major impact is on bone health. Persistently high PTH levels cause calcium to be continuously drawn from the bones, making them weak and brittle. This can result in increased fracture risk and a specific type of bone disease called renal osteodystrophy, particularly in individuals with kidney disease.
The cardiovascular system is also affected by prolonged SHPT. Elevated levels of calcium and phosphate in the blood can lead to vascular calcification, a process where calcium deposits accumulate in blood vessels, causing them to harden. This calcification increases the risk of heart disease. Individuals might also experience symptoms, such as fatigue, muscle weakness, and joint pain, due to the ongoing mineral imbalances or the underlying condition driving SHPT.
Identifying and Treating the Condition
Identifying secondary hyperparathyroidism typically involves specific blood tests. Healthcare providers will measure parathyroid hormone (PTH) levels, which will be elevated. Blood calcium levels may be normal or low in the early stages, while phosphate levels are often high, especially in the context of kidney disease. Vitamin D levels are commonly found to be low.
Treatment for SHPT focuses on lowering PTH levels, correcting mineral imbalances, and addressing the underlying cause. Managing the primary condition, such as optimizing kidney function in chronic kidney disease or supplementing vitamin D in cases of deficiency, is a foundational step. Medications commonly used include vitamin D analogues, which help improve calcium absorption and suppress PTH production.
Calcimimetics are another class of drugs that make the parathyroid glands more sensitive to existing calcium, thereby reducing PTH release. In patients with kidney disease, phosphate binders are often prescribed to reduce the absorption of phosphate from food. In severe cases where medical management is insufficient, surgical removal of part or all of the parathyroid glands, known as parathyroidectomy, may be considered as a last resort.