Hyperparathyroidism
Primary hyperparathyroidism is the most common cause of hypercalcemia in outpatients, caused by autonomous overproduction of parathyroid hormone (PTH) -- usually by a single benign parathyroid adenoma. Mild hypercalcemia may be asymptomatic and found on routine labs. Moderate to severe hypercalcemia causes a broad range of symptoms affecting multiple organ systems.
Symptoms
The classic mnemonic is 'bones, stones, groans, and psychic moans': osteoporosis (bone loss), nephrolithiasis (kidney stones), gastrointestinal symptoms (nausea, constipation, abdominal pain), and neurocognitive effects (fatigue, cognitive slowing, depression, anxiety). Many patients are asymptomatic on current surveillance criteria.
Causes and risk
A single parathyroid adenoma is responsible in 85% of cases. Multigland hyperplasia accounts for 15%. Parathyroid carcinoma is rare (less than 1%). Risk factors include previous head and neck radiation, lithium use, and MEN syndromes.
How it is evaluated
Elevated calcium with inappropriately normal or elevated PTH confirms primary hyperparathyroidism. We check 24-hour urine calcium (to exclude familial hypocalciuric hypercalcemia), 25-OH-D, creatinine, and phosphorus. Sestamibi nuclear scan and ultrasound localize the adenoma preoperatively. DEXA assesses bone impact.
Treatment
Parathyroidectomy is the only curative treatment and is recommended for symptomatic disease and most asymptomatic patients under age 50, or with hypercalcemia above 1 mg/dL above the upper limit of normal, T-score below −2.5, eGFR below 60, or a kidney stone. For patients not undergoing surgery, we monitor calcium, creatinine, and DEXA every 1 -- 2 years.