Endocrinology · Calcium Metabolism
The facts most likely to be tested
The most common cause of primary hyperparathyroidism is a solitary parathyroid adenoma.
Laboratory findings classically reveal hypercalcemia with an inappropriately elevated or normal parathyroid hormone (PTH) level.
Patients frequently present with the mnemonic 'stones, bones, abdominal groans, and psychiatric overtones'.
Sestamibi scintigraphy is the preferred preoperative localization study to identify the hyperfunctioning gland.
Surgical parathyroidectomy is the definitive treatment for symptomatic patients or those meeting specific biochemical criteria.
Osteitis fibrosa cystica, characterized by subperiosteal resorption and brown tumors, is a classic skeletal manifestation of severe disease.
Familial hypocalciuric hypercalcemia (FHH) must be excluded by checking a 24-hour urine calcium before proceeding to surgery.
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A 58-year-old woman presents to the clinic for a routine physical exam. She reports a history of recurrent nephrolithiasis and generalized fatigue. Laboratory studies reveal a serum calcium of 11.8 mg/dL and an elevated PTH level of 95 pg/mL. Her 24-hour urine calcium is high, effectively ruling out familial hypocalciuric hypercalcemia. Physical examination is unremarkable, and she denies any abdominal pain or psychiatric symptoms.
What is the most appropriate next step in the management of this patient?
Parathyroidectomy
The patient meets the criteria for surgery due to symptomatic hypercalcemia (nephrolithiasis) and elevated serum calcium, confirming the diagnosis of primary hyperparathyroidism.
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Etiology / Epidemiology
Most common cause is a parathyroid adenoma (85%). Primarily affects postmenopausal women.
Clinical Manifestations
Classic bones, stones, abdominal groans, and psychic overtones. Hypercalcemia is the hallmark.
Diagnosis
Gold standard is elevated PTH with hypercalcemia. Sestamibi scan for localization.
Treatment
Definitive treatment is parathyroidectomy. Avoid thiazide diuretics.
Prognosis
High cure rate with surgery. Monitor for hungry bone syndrome post-op.
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Epidemiology & Etiology
Primary hyperparathyroidism is most frequently caused by a solitary parathyroid adenoma. It is significantly more common in postmenopausal women and may be associated with MEN 1 or MEN 2A syndromes. Rarely, it results from parathyroid hyperplasia or carcinoma.
Pertinent Anatomy
The four parathyroid glands are typically located posterior to the thyroid. Ectopic glands can reside in the mediastinum, complicating surgical localization. Understanding this anatomy is critical for the Sestamibi scan used in preoperative planning.
Pathophysiology
Autonomous overproduction of PTH leads to increased osteoclast activity, causing bone resorption and calcium release. Concurrently, PTH increases renal calcium reabsorption and stimulates 1,25-dihydroxyvitamin D production. This results in persistent hypercalcemia and hypophosphatemia.
Clinical Manifestations
Patients often present with bones, stones, abdominal groans, and psychic overtones. Nephrolithiasis is a frequent complication due to hypercalciuria. Red flags include shortened QT interval on EKG, severe constipation, and altered mental status.
Diagnosis
The diagnosis is confirmed by elevated serum calcium and inappropriately elevated PTH. A 24-hour urine calcium is required to rule out familial hypocalciuric hypercalcemia. Sestamibi scan is the gold standard for preoperative localization of the adenoma.
Treatment
The parathyroidectomy is the definitive treatment for symptomatic patients. For those who cannot undergo surgery, cinacalcet is used to lower calcium levels. Avoid thiazide diuretics as they decrease urinary calcium excretion and worsen hypercalcemia.
Prognosis
Surgical cure rates exceed 95%. Post-operative monitoring is essential to detect hungry bone syndrome, characterized by severe, symptomatic hypocalcemia as bone remineralization occurs rapidly.
Differential Diagnosis
Familial hypocalciuric hypercalcemia: low urinary calcium excretion
Malignancy: suppressed PTH levels
Thiazide diuretic use: resolves after discontinuation
Granulomatous disease: elevated 1,25-dihydroxyvitamin D
Lithium therapy: associated with elevated PTH and calcium