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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • Inappropriately normal or elevated parathyroid hormone (PTH) levels

  • Serum calcium level above upper limit of normal (> 10 mg/dL) corrected for serum albumin, or ionized calcium level higher than upper limit of normal range

  • Increased 24-hour urine calcium excretion (> 200 mg)

  • Elevated alkaline phosphatase

  • Decreased serum phosphate level

  • Elevated serum calcium due to parathyroid hormone excess

GENERAL CONSIDERATIONS

  • PTH mainly regulates ionized calcium levels in the blood by interacting with bone, intestinal mucosa, and the kidney. PTH has few direct effects on the heart but can affect the cardiovascular system through its regulation of calcium

  • The most common cause of hyperparathyroidism is overproduction of PTH from a parathyroid adenoma

  • Secondary hyperparathyroidism is seen with chronic hypocalcemia, vitamin D deficiency, or renal failure

  • Tertiary hyperparathyroidism occurs when secondary hyperparathyroidism becomes autonomous, as in renal failure

  • Rarely, PTH overproduction can occur with parathyroid hyperplasia as part of multiple endocrine neoplasms

  • Secondary causes of hypercalcemia must be excluded such as granulomatous disease, excess calcium ingestion, vitamin D and A toxicity, thyrotoxicosis, adrenal insufficiency, and malignancies

  • Increased calcium can adversely affect the cardiovascular system and lead to hypertension, arrhythmias, and calcification of heart and vascular structures

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • Most patients are asymptomatic

  • Some patients report a variety of nonspecific symptoms

PHYSICAL EXAM FINDINGS

  • Calcium deposits in the cornea, soft tissue, and joints

  • Signs of left ventricular hypertrophy or valve sclerosis

  • Bradycardia and hypertension may occur with acute hypercalcemia

DIFFERENTIAL DIAGNOSIS

  • Other causes of hypercalcemia without PTH excess

  • Valvular sclerosis from other causes

  • Other causes of hypertension and left ventricular hypertrophy

DIAGNOSTIC EVALUATION

LABORATORY TESTS

  • Elevated serum calcium and ionized calcium

  • Inappropriately normal or high PTH level

  • Other causes of high calcium are associated with low PTH levels

  • Low serum phosphate levels

  • Hyperchloremic metabolic acidosis, elevated serum chloride, reduced carbon dioxide

  • Elevated alkaline phosphatase levels, especially with hyperparathyroid bone disease

ELECTROCARDIOGRAPHY

  • Shortened ST segment and decreased QT interval

  • With serum calcium levels > 16 mg/dL, the T wave widens, prolonging the QT interval

IMAGING STUDIES

  • Echocardiography: shows left ventricular hypertrophy and calcification of the aortic root and aortic and mitral valves

  • Chest x-ray: calcification of the coronary arteries and aorta

TREATMENT

CARDIOLOGY REFERRAL

  • Suspected cardiac disease

HOSPITALIZATION CRITERIA

  • Planned surgery

MEDICATIONS

  • Pharmacologic treatment with bisphosphonates, pamidronate, risedronate, cinacalcet, and high-dose estrogen in postmenopausal women is less effective than surgery

  • Acute hypercalcemia is treated with saline infusion plus furosemide

  • Thiazide diuretics are contraindicated

SURGERY
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