Hyperparathyroidism Cheat Sheet

Hyperparathyroidism Hyperparathyroidism is a condition characterized by excessive secretion of parathyroid hormone (PTH) by the parathyroid glands. This hormone plays a crucial role in regulating calcium levels in the blood. There are three types of hyperparathyroidism: primary, secondary, and tertiary. Each type has distinct causes, pathophysiology, and clinical features. Primary Hyperparathyroidism Etiology and Pathophysiology: Primary hyperparathyroidism (PHPT) is caused by the autonomous overproduction of PTH. This is often due to a benign parathyroid adenoma (85% of cases), hyperplasia of the parathyroid glands (15%), or, rarely, parathyroid carcinoma (<1%). The excessive PTH secretion results in hypercalcemia and hypophosphatemia, as PTH increases calcium reabsorption in the kidneys, mobilizes calcium from bones, and increases intestinal calcium absorption through its effect on vitamin D metabolism. Clinical Features: Patients with PHPT may be asymptomatic or present with symptoms related to hypercalcemia, such as:      Kidney stones (nephrolithiasis) Bone pain and fractures due to osteitis fibrosa cystica Muscle weakness and fatigue Neuropsychiatric symptoms, including depression and cognitive dysfunction Gastrointestinal symptoms like constipation, peptic ulcers, and pancreatitis Diagnosis: Diagnosis involves detecting elevated serum calcium and PTH levels. Imaging studies, such as a sestamibi scan, ultrasound, or MRI, can localize parathyroid adenomas. Management: Surgical removal of the affected parathyroid gland(s) is the definitive treatment. Medical management, including hydration, bisphosphonates, and calcimimetics, may be used for patients who are not surgical candidates. Secondary Hyperparathyroidism Etiology and Pathophysiology: Secondary hyperparathyroidism (SHPT) occurs in response to chronic hypocalcemia and is most commonly associated with chronic kidney disease (CKD). In CKD, impaired renal function leads to phosphate retention and reduced production of active vitamin D (calcitriol), resulting in hypocalcemia. This stimulates the parathyroid glands to secrete more PTH in an attempt to normalize calcium levels. Clinical Features: Symptoms of SHPT are primarily related to the underlying cause (e.g., CKD) and may include:      Bone pain and skeletal deformities due to renal osteodystrophy Muscle weakness Calcification of soft tissues and vascular calcification Pruritus (itching) Symptoms related to CKD, such as anemia, fluid overload, and hypertension Diagnosis: Diagnosis involves finding elevated PTH levels in the context of hypocalcemia or normocalcemia and hyperphosphatemia, typically in patients with known CKD. Serum phosphate, calcium, and vitamin D levels are also assessed. Management: Treatment focuses on managing the underlying cause and may include:     Phosphate binders to reduce serum phosphate levels Vitamin D analogs or calcitriol to increase calcium absorption Calcimimetics to decrease PTH secretion Dialysis in advanced CKD Tertiary Hyperparathyroidism Etiology and Pathophysiology: Tertiary hyperparathyroidism (THPT) occurs when secondary hyperparathyroidism becomes autonomous and excessive, usually after longstanding SHPT, particularly in patients with end-stage renal disease (ESRD). The parathyroid glands become hyperplastic and continue to secrete PTH independently of calcium levels, leading to hypercalcemia. Clinical Features: The clinical manifestations of THPT are similar to those of PHPT and SHPT but can be more severe due to prolonged and elevated PTH levels:    Persistent hypercalcemia Symptoms of hypercalcemia (kidney stones, bone pain, neuropsychiatric symptoms) Calciphylaxis, a severe form of vascular calcification leading to skin necrosis Diagnosis: Diagnosis is made by identifying elevated serum calcium and PTH levels in patients with a history of prolonged SHPT, typically in the context of CKD or post-renal transplantation. Management: The primary treatment for THPT is surgical, typically a subtotal parathyroidectomy or total parathyroidectomy with autotransplantation of parathyroid tissue. Medical management includes similar approaches as SHPT but often requires more aggressive treatment due to the severity of the condition. Summary In summary, hyperparathyroidism can be classified into primary, secondary, and tertiary forms, each with distinct etiologies and clinical presentations. PHPT is caused by autonomous parathyroid gland activity, SHPT by chronic hypocalcemia often due to CKD, and THPT by the autonomous hyperfunction of the parathyroid glands after prolonged SHPT. Understanding these differences is crucial for appropriate diagnosis and management.