HYPERPARATHYROIDISM
GENERAL FEATURES
• Hyperparathyroidism is an endocrine disorder caused by chronic, excessive secretion of parathyroid hormone from one or more of the parathyroid glands as a result of a parathyroid adenoma or carcinoma.
• Single parathyroid adenomas are the most common cause, accounting for approximately 80% of cases. Multiple parathyroid adenomas and carcinoma are much less common, accounting for 20% and less than 1% of cases, respectively. A small number of patients may have hyperparathyroidism as a result of multiple endocrine neoplasia.
• Hypercalcemia is often detected on routine screening laboratory tests in asymptomatic patients.
• Signs and symptoms can generally be correlated to the development and extent of hypercalcemia and increased parathyroid hormone (PTH) secretion. Symptomatic patients are noted to have problems with “bones, stones, abdominal groans, psychic moans, with fatigue overtones.”
• Parathyroid adenomas are rarely palpable because of their size and location.
• Normocalcemic hyperparathyroidism may be found in patients during a workup for decreased bone mineral density. Serum calcium levels may be normal but PTH levels will be increased.
CLINICAL ASSESSMENT
• Musculoskeletal: osteitis fibrosa cystica is the hallmark sign of hyperparathyroidism; however, osteopenia is a more common finding. Osteitis fibrosa cystica involves bone pain, decalcification of bone, “salt and pepper” appearance of the skull, bone cysts, and brown tumors of the long bones. Patients may also report myopathy and weakness.
• GU: nephrolithiasis, nephrocalcinosis, and chronic renal insufficiency; patients may also have decreased urine concentrating ability manifesting as increased urination and thirst.
• GI: nausea, vomiting, abdominal pain, anorexia, constipation
• CNS: lethargy, depression, psychosis, and cognitive dysfunction
DIAGNOSIS
• Elevated serum ionized calcium (with adjusted calcium used for hypoalbuminemic patients), low serum phosphorus, and normal or elevated alkaline phosphatase
• Normochromic, normocytic anemia
• Elevated serum PTH. Intact PTH concentration can distinguish hyperparathyroidism from hypercalcemia when serum calcium is >12 mg/dL.
• Hypercalcemia may cause shortening of the QT interval. subperiosteal bone resorption.
• Elevated BUN and creatinine may show renal insufficiency.
TREATMENT
• Patients should be instructed to consume 3 to 5 liters of fluid per day and 1,000 mg calcium.
• Surgery is the primary treatment, particularly for patients younger than 50 years and those with complications from hyperparathyroidism.
• Observation is acceptable approach in asymptomatic patients with mildly elevated calcium level (<12 mg/dL), no osteoporosis, normal kidney function, no history of life-threatening hypercalcemia.
• Bisphosphonates are recommended for patients with osteopenia or osteoporosis in addition to treatment.
• Cinacalcet (Sensipar), an oral calcimimetic that lowers calcium and PTH levels, may be used to treat secondary hyperparathyroidism in patients with chronic kidney disease on dialysis and those with hypercalcemia of malignancy. It is not recommended for the treatment of primary hyperparathyroidism. JAAPA
QUESTIONS & ANSWERS
1. You detect a calcium level of 12.5 mg/dL during a routine laboratory evaluation of a 58-year-old asymptomatic man. You order the following follow-up test:
a. Parathyroid hormone
b. CBC
c. Intravenous pyelogram
d. Chest radiography
Answer: a
Explanation: Parathyroid hormone testing is used as a confirmatory test for hyperparathyroidism when elevated calcium is noted.
2. Your 50-year-old female patient complains of a history of kidney stones, osteopenia, fatigue, nausea, and constipation. You order laboratory tests and expect the following results:
a. Decreased serum calcium
b. Increased serum phosphorus
c. Normal BUN/creatinine
d. Elevated serum calcium
Answer: d
Explanation: Elevated serum calcium, decreased serum phosphorus, and elevated BUN/creatinine are all laboratory test results expected in hyperparathyroidism.
Dawn Colomb-Lippa is professor of physician assistant studies at Quinnipiac University, Hamden, Connecticut. Amy Klingler practices in primary care at the Salmon River Clinic, Stanley, Idaho. The authors are department editors for the Quick Recertification Series and members of the JAAPA editorial board.