Parathyroid hormone (PTH) plays a central role in maintaining the body’s delicate balance of calcium. Elevated PTH levels suggest an imbalance in this system. This article clarifies PTH’s function and explores the common causes and implications of its elevation.
Understanding Parathyroid Hormone
Parathyroid hormone is produced by the parathyroid glands, four small glands located in the neck, behind the thyroid gland. This hormone regulates calcium and phosphorus levels in the blood, essential for nerve, muscle function, and bone health. When blood calcium levels fall, the parathyroid glands increase PTH secretion to restore balance. PTH signals bones to release stored calcium, instructs kidneys to reabsorb more calcium and excrete excess phosphorus, and promotes vitamin D activation to enhance intestinal calcium absorption.
Common Causes of Elevated PTH
Elevated parathyroid hormone levels stem from several distinct conditions. The most frequent is primary hyperparathyroidism, a direct issue within the parathyroid glands. This condition occurs when a single benign growth (adenoma) develops on one gland, leading to PTH overproduction. Less commonly, overproduction results from enlargement of two or more glands (hyperplasia) or, rarely, a cancerous tumor. In primary hyperparathyroidism, excessive PTH directly leads to high blood calcium.
Another significant cause of elevated PTH is secondary hyperparathyroidism, which arises from persistently low blood calcium levels. This often happens due to chronic kidney disease, where kidneys cannot properly activate vitamin D or excrete phosphorus, contributing to lower blood calcium. A lack of sufficient vitamin D, from inadequate intake or limited sun exposure, also lowers calcium absorption, prompting increased PTH production. Conditions impairing nutrient absorption, such as celiac disease or gastric bypass surgery, can also lead to calcium and vitamin D deficiencies, triggering secondary hyperparathyroidism.
Sometimes, long-standing secondary hyperparathyroidism can progress to tertiary hyperparathyroidism. This occurs when the parathyroid glands, after prolonged overstimulation, become autonomously overactive and continue to produce excessive PTH, even if the initial cause of low calcium has been corrected. Tertiary hyperparathyroidism is most frequently observed in individuals with chronic kidney disease.
Recognizing Symptoms of High PTH
Symptoms associated with chronically elevated PTH often result from high blood calcium, a condition called hypercalcemia. These symptoms can be subtle, non-specific, or in some instances, may not be noticeable at all, leading to incidental discovery during routine blood tests. When symptoms manifest, they can affect various bodily systems.
Symptoms include persistent fatigue, general weakness, and joint or bone pain, arising from calcium being drawn out of the bones. Patients may also experience an increased risk of bone fractures and osteoporosis.
Excess calcium makes kidneys work harder, leading to increased thirst, frequent urination, and potential kidney stones. Digestive issues such as constipation, nausea, or a diminished appetite can also occur.
Additionally, cognitive changes like memory problems, difficulty concentrating, or feelings of depression may be present.
Diagnosis and Management of High PTH
If elevated PTH levels are discovered, consult a healthcare provider for diagnosis and management. Diagnosis typically involves blood tests to measure PTH, calcium, phosphorus, and vitamin D levels, along with an assessment of kidney function. A 24-hour urine collection to measure calcium excretion may also be performed. Imaging studies like DEXA scans to assess bone density, or specific parathyroid scans, such as a sestamibi scan, might identify an overactive gland.
The approach to management depends significantly on the underlying cause of the elevated PTH. For primary hyperparathyroidism, treatment options range from careful monitoring for mild cases to surgical removal of the overactive gland(s), known as parathyroidectomy. Surgery is often a highly effective treatment for primary hyperparathyroidism, leading to a return to normal calcium levels in most individuals.
For secondary hyperparathyroidism, the focus of management is on addressing the root cause. This can involve managing chronic kidney disease, providing vitamin D supplementation for deficiencies, or making dietary adjustments and using medications like phosphate binders or calcimimetics. With accurate diagnosis and appropriate management, elevated PTH levels and their associated complications can often be effectively controlled.