Secondary hyperparathyroidism (SHPT) is a medical condition where the parathyroid glands, typically four small glands located in the neck near the thyroid, produce an excessive amount of parathyroid hormone (PTH). This overproduction occurs in response to an underlying health issue, rather than a primary problem with the glands themselves. Most commonly, SHPT develops in individuals with chronic kidney disease (CKD).
Understanding the Condition and Treatment Objectives
Secondary hyperparathyroidism develops in individuals with chronic kidney disease because failing kidneys disrupt the body’s mineral balance. Healthy kidneys are responsible for removing excess phosphate from the body and converting vitamin D into its active form, which is necessary for calcium absorption. When kidney function declines, phosphate levels in the blood can rise, and active vitamin D production decreases, leading to lower blood calcium levels. This imbalance signals the parathyroid glands to produce more PTH in an attempt to restore calcium levels, causing the glands to enlarge and become overactive.
Treatment for secondary hyperparathyroidism aims to reduce elevated PTH levels and normalize blood calcium and phosphate. Restoring these mineral balances helps prevent or treat bone disease, known as renal osteodystrophy, and mitigate the risk of cardiovascular complications that can arise from prolonged mineral imbalances.
Pharmacological Approaches
Medical management is often the initial strategy for treating secondary hyperparathyroidism, involving several classes of medications. Phosphate binders are a common treatment, working by attaching to dietary phosphate in the digestive tract. This action prevents the absorption of phosphate into the bloodstream, helping to manage high phosphate levels often seen in kidney disease. Examples of these medications include sevelamer and lanthanum carbonate.
Vitamin D receptor activators (VDRAs) represent another important class of drugs. These synthetic forms of vitamin D, such as paricalcitol and doxercalciferol, help suppress the overproduction of PTH. They also contribute to improving the balance of calcium and phosphate in the body, even when kidney function is impaired.
Calcimimetics, including cinacalcet and etelcalcetide, directly influence the parathyroid glands. These medications increase the sensitivity of the calcium-sensing receptors on the parathyroid glands to existing calcium levels. This heightened sensitivity prompts the glands to reduce their secretion of PTH, thereby lowering circulating PTH levels.
When Surgery is Considered
Surgery, specifically parathyroidectomy, is a treatment option reserved for severe cases of secondary hyperparathyroidism that do not adequately respond to medical therapies. This procedure involves the surgical removal of one or more of the overactive parathyroid glands. It is typically considered when patients experience persistent, significantly elevated PTH levels despite optimal medical management, or when they develop severe symptoms.
Such symptoms can include intractable bone pain, a condition called calciphylaxis (a rare but serious calcification of blood vessels in the skin and soft tissues), or dangerously high calcium levels in the blood. Surgical approaches can vary, including subtotal parathyroidectomy, where part of the glands are removed, or total parathyroidectomy with autotransplantation, where all glands are removed and a small portion of one gland is re-implanted elsewhere in the body.
Nutritional and Lifestyle Management
Beyond medical and surgical interventions, nutritional and lifestyle adjustments play a significant role in managing secondary hyperparathyroidism. Dietary modifications are important, particularly limiting the intake of phosphate-rich foods. This includes reducing consumption of processed foods, certain dairy products, nuts, and sodas, which can contribute to higher phosphate levels in the blood.
Managing fluid intake is also a consideration for individuals with chronic kidney disease, as it impacts overall fluid and electrolyte balance. Regular monitoring of blood levels for PTH, calcium, phosphate, and vitamin D is also an important part of a comprehensive care plan, allowing healthcare providers to adjust treatments as needed.