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Hypercalcemia

by James L. Lewis, III, MD

Hypercalcemia is total serum Ca concentration > 10.4 mg/dL (> 2.60 mmol/L) or ionized serum Ca > 5.2 mg/dL (> 1.30 mmol/L). Principal causes include hyperparathyroidism, vitamin D toxicity, and cancer. Clinical features include polyuria, constipation, muscle weakness, confusion, and coma. Diagnosis is by serum ionized Ca and parathyroid hormone concentrations. Treatment to increase Ca excretion and reduce bone resorption of Ca involves saline, Na diuresis, and drugs such as pamidronate.

Etiology

Hypercalcemia usually results from excessive bone resorption. There are many causes of hypercalcemia (see Principal Causes of Hypercalcemia), but the most common are hyperparathyroidism and cancer.

Principal Causes of Hypercalcemia

Category

Examples

Excessive bone resorption

Cancer with bone metastases

Carcinoma

Leukemia

Lymphoma

Multiple myeloma

Immobilization

Orthopedic casting or traction

Paget disease of bone

Osteoporosis in the elderly

Paraplegia or quadriplegia

Young, growing patients

Parathyroid hormone excess

Familial hypocalciuric hypercalcemia

Parathyroid carcinoma

Primary hyperparathyroidism

Secondary hyperparathyroidism

Tertiary hyperparathyroidism

Vitamin toxicity

Vitamin A toxicity

Vitamin D toxicity

Other disorders

Hyperthyroidism

Humoral hypercalcemia of cancer (ie, hypercalcemia of cancer in the absence of bone metastases)

Excessive GI Ca absorption, intake, or both

Sarcoidosis and other granulomatous diseases

Berylliosis

Coccidioidomycosis

Histoplasmosis

Leprosy

Silicosis

TB

Other disorders

Milk-alkali syndrome

Vitamin D toxicity

Elevated plasma protein concentration

Uncertain mechanism

Drugs

Lithium toxicity

Theophylline toxicity

Thiazide treatment

Endocrine dysfunction

Addison disease

Cushing disease, postoperative

Myxedema

Other disorders

Aluminum-induced osteomalacia

Idiopathic infantile hypercalcemia

Neuroleptic malignant syndrome

Artifactual

Exposure of blood to contaminated glassware

Prolonged venous stasis as blood sample was obtained

Pathophysiology

Primary hyperparathyroidism is a generalized disorder resulting from excessive secretion of parathyroid hormone (PTH) by one or more parathyroid glands. It probably is the most common cause of hypercalcemia, particularly among patients who are not hospitalized. Incidence increases with age and is higher in postmenopausal women. It also occurs in high frequency 3 decades after neck irradiation. Familial and sporadic forms exist. Familial forms due to parathyroid adenoma occur in patients with other endocrine tumors (see Overview of Multiple Endocrine Neoplasias). Primary hyperparathyroidism causes hypophosphatemia and excessive bone resorption. Although asymptomatic hypercalcemia is the most frequent presentation, nephrolithiasis is also common, particularly when hypercalciuria occurs due to long-standing hypercalcemia. Histologic examination shows a parathyroid adenoma in about 85% of patients with primary hyperparathyroidism, although it is sometimes difficult to distinguish an adenoma from a normal gland. About 15% of cases are due to hyperplasia of 2 glands. Parathyroid cancer occurs in < 1% of cases.

The syndrome of familial hypocalciuric hypercalcemia (FHH) is transmitted as an autosomal dominant trait. Most cases involve an inactivating mutation of the Ca-sensing receptor gene, resulting in higher concentrations of serum Ca being needed to inhibit PTH secretion. Subsequent PTH secretion induces renal phosphate (PO 4 ) excretion. Persistent hypercalcemia (usually asymptomatic) and often from an early age, normal to slightly elevated concentrations of PTH, hypocalciuria, and hypermagnesemia occur. Renal function is normal, and nephrolithiasis is unusual. However, severe pancreatitis occasionally occurs. This syndrome, which is associated with parathyroid hyperplasia, is not relieved by subtotal parathyroidectomy.

Secondary hyperparathyroidism occurs most commonly in advanced chronic kidney disease when decreased formation of active vitamin D in the kidneys and other factors lead to hypocalcemia and chronic stimulation of PTH secretion. Hyperphosphatemia that develops in response to chronic kidney disease also contributes. Once established, hypercalcemia or normocalcemia may occur. The sensitivity of the parathyroid to Ca may be diminished because of pronounced glandular hyperplasia and elevation of the Ca set point (ie, the amount of Ca necessary to reduce secretion of PTH).

Tertiary hyperparathyroidism results in autonomous hypersecretion of PTH regardless of serum Ca concentration. Tertiary hyperparathyroidism generally occurs in patients with long-standing secondary hyperparathyroidism, as in patients with end-stage renal disease of several years’ duration.

Cancer is a common cause of hypercalcemia, usually in hospitalized patients. Although there are several mechanisms, elevated serum Ca ultimately occurs as a result of bone resorption. Humoral hypercalcemia of cancer (ie, hypercalcemia with no or minimal bone metastases) occurs most commonly with squamous cell carcinoma, renal cell carcinoma, breast cancer, prostate cancer, and ovarian cancer. Many cases of humoral hypercalcemia of cancer were formerly attributed to ectopic production of PTH. However, some of these tumors secrete a PTH-related peptide that binds to PTH receptors in both bone and kidney and mimics many of the effects of the hormone, including osteoclastic bone resorption. Hematologic cancers, most often multiple myeloma, but also certain lymphomas and lymphosarcomas, cause hypercalcemia by elaborating a group of cytokines that stimulate osteoclasts to resorb bone, resulting in osteolytic lesions, diffuse osteopenia, or both. Hypercalcemia may result from local elaboration of osteoclast-activating cytokines or prostaglandins, direct bone resorption by the metastatic tumor cells, or both.

Vitamin D toxicity can be caused by high concentrations of endogenous 1,25(OH) 2 D. Although serum concentrations are low in most patients with solid tumors, patients with lymphoma and T-cell leukemia sometimes have elevated concentrations due to dysregulation of the 1-α-hydroxylase enzyme present in tumor cells. Exogenous vitamin D in pharmacologic doses causes excessive bone resorption as well as increased intestinal Ca absorption, resulting in hypercalcemia and hypercalciuria (see Vitamin D Toxicity).

Granulomatous disorders , such as sarcoidosis, TB, leprosy, berylliosis, histoplasmosis, and coccidioidomycosis, lead to hypercalcemia and hypercalciuria. In sarcoidosis, hypercalcemia and hypercalciuria appear to be due to unregulated conversion of 25(OH)D to 1,25(OH) 2 D, presumably due to expression of the 1-α-hydroxylase enzyme in mononuclear cells within sarcoid granulomas. Similarly, elevated serum concentrations of 1,25(OH) 2 D have been reported in hypercalcemic patients with TB and silicosis. Other mechanisms must account for hypercalcemia in some instances, because depressed 1,25(OH) 2 D concentrations occur in some patients with hypercalcemia and leprosy.

Immobilization , particularly complete prolonged bed rest in patients at risk (see Principal Causes of Hypercalcemia), can result in hypercalcemia due to accelerated bone resorption. Hypercalcemia develops within days to weeks of onset of bed rest. Reversal of hypercalcemia occurs promptly on resumption of weight bearing. Young adults with several bone fractures and people with Paget disease of bone are particularly prone to hypercalcemia when at bed rest.

Idiopathic infantile hypercalcemia (Williams syndrome—see Table: Examples of Contiguous Gene Deletion Syndromes) is an extremely rare sporadic disorder with dysmorphic facial features, cardiovascular abnormalities, renovascular hypertension, and hypercalcemia. PTH and vitamin D metabolism are normal, but the response of calcitonin to Ca infusion may be abnormal.

In milk-alkali syndrome , excessive amounts of Ca and absorbable alkali are ingested, usually during self-treatment with Ca carbonate antacids for dyspepsia or to prevent osteoporosis, resulting in hypercalcemia, metabolic alkalosis, and renal insufficiency. The availability of effective drugs for peptic ulcer disease and osteoporosis has greatly reduced the incidence of this syndrome.

Symptoms and Signs

In mild hypercalcemia, many patients are asymptomatic. Clinical manifestations of hypercalcemia include constipation, anorexia, nausea and vomiting, abdominal pain, and ileus. Impairment of the renal concentrating mechanism leads to polyuria, nocturia, and polydipsia. Elevation of serum Ca > 12 mg/dL (> 3.00 mmol/L) can cause emotional lability, confusion, delirium, psychosis, stupor, and coma. Hypercalcemia may cause neuromuscular symptoms, including skeletal muscle weakness. Hypercalciuria with nephrolithiasis is common. Less often, prolonged or severe hypercalcemia causes reversible acute renal failure or irreversible renal damage due to nephrocalcinosis (precipitation of Ca salts within the kidney parenchyma). Peptic ulcers and pancreatitis may occur in patients with hyperparathyroidism for reasons that are not related to hypercalcemia.

Severe hypercalcemia causes a shortened QT c interval on ECG, and arrhythmias may occur, particularly in patients taking digoxin. Hypercalcemia > 18 mg/dL (> 4.50 mmol/L) may cause shock, renal failure, and death.

Diagnosis

  • Total serum Ca concentration

  • Chest x-ray; measurement of electrolytes, BUN, creatinine, ionized Ca, PO 4 , PTH, alkaline phosphatase, and serum protein immunoelectrophoresis to determine the cause

  • Sometimes PTH and urinary excretion of Ca with or without PO 4

Hypercalcemia is diagnosed by a serum Ca concentration > 10.4 mg/dL (> 2.60 mmol/L) or ionized serum Ca > 5.2 mg/dL (> 1.30 mmol/L). The condition is frequently discovered during routine laboratory screening. Serum Ca can be artifactually elevated (see Laboratory and Clinical Findings in Some Disorders Causing Hypercalcemia). Hypercalcemia can also be masked by low serum protein. When protein and albumin are abnormal and when ionized hypercalcemia is suspected because of clinical findings (eg, because of symptoms of hypercalcemia), ionized serum Ca should be measured.

Initial evaluation

Initial evaluation should include a review of the history, particularly of past serum Ca concentration; physical examination; a chest x-ray; and laboratory studies, including electrolytes, BUN, creatinine, ionized Ca, PO 4 , PTH, alkaline phosphatase, and serum protein immunoelectrophoresis. The cause is apparent from clinical data and results of these tests in 95% of patients. Patients without an obvious cause of hypercalcemia after this evaluation should undergo measurement of intact PTH and 24-h urinary Ca.

Asymptomatic hypercalcemia that has been present for years or is present in several family members raises the possibility of FHH. Primary hyperparathyroidism generally manifests late in life but can be present for several years before symptoms occur. When no cause is obvious, concentrations of serum Ca < 11 mg/dL (< 2.75 mmol/L) suggest hyperparathyroidism or other nonmalignant causes, whereas concentration > 13 mg/dL (> 3.25 mmol/L) suggest cancer.

Measurement of intact PTH levels help differentiate PTH-mediated hypercalcemia (eg, caused by hyperparathyroidism or FHH), in which PTH levels are high or high-normal, from most other (PTH-independent) causes. In PTH-independent causes, levels are usually < 20 pg/mL.

The chest x-ray is particularly helpful, revealing most granulomatous disorders, such as TB, sarcoidosis, and silicosis, as well as primary lung cancer and lytic and Paget lesions in bones of the shoulder, ribs, and thoracic spine.

Chest and bone (eg, skull, extremity) x-rays can also show the effects on bone of secondary hyperparathyroidism, most commonly in long-term dialysis patients. In osteitis fibrosa cystica (often due to primary hyperparathyroidism), increased osteoclastic activity from overstimulation by PTH causes rarefaction of bone with fibrous degeneration and cyst and fibrous nodule formation. Because characteristic bone lesions occur only with relatively advanced disease, bone x-rays are recommended only for symptomatic patients. X-rays typically show bone cysts, a heterogeneous appearance of the skull, and subperiosteal resorption of bone in the phalanges and distal clavicles.

Hyperparathyroidism

In hyperparathyroidism, the serum Ca is rarely > 12 mg/dL (> 3.00 mmol/L), but the ionized serum Ca is almost always elevated. Low serum PO 4 concentration suggests hyperparathyroidism, especially when coupled with elevated PO 4 renal excretion. When hyperparathyroidism results in increased bone turnover, serum alkaline phosphatase is frequently increased. Increased intact PTH, particularly inappropriate elevation (ie, a high concentration in the absence of hypocalcemia) or an inappropriate high-normal concentration (ie, despite hypercalcemia), is diagnostic. Urinary Ca excretion is usually normal or high in hyperparathyroidism. Chronic kidney disease suggests the presence of secondary hyperparathyroidism, but primary hyperparathyroidism can also be present. In patients with chronic kidney disease, high serum Ca and normal serum PO 4 suggest primary hyperparathyroidism, whereas elevated PO 4 suggests secondary hyperparathyroidism.

The need for localization of parathyroid tissue before surgery on the parathyroid(s) is controversial. High-resolution CT with or without CT-guided biopsy and immunoassay of thyroid venous drainage, MRI, high-resolution ultrasonography, digital subtraction angiography, and thallium-201–technetium-99 scanning all have been used and are highly accurate, but they have not improved the usually high cure rate of parathyroidectomy done by experienced surgeons. Technetium-99 sestamibi, a newer radionuclide agent for parathyroid imaging, is more sensitive and specific than older agents and may be useful for identifying solitary adenomas.

For residual or recurrent hyperparathyroidism after initial parathyroid surgery, imaging is necessary and may reveal abnormally functioning parathyroid glands in unusual locations throughout the neck and mediastinum. Technetium-99 sestamibi is probably the most sensitive imaging test. Use of several imaging studies (MRI, CT, or high-resolution ultrasonography in addition to technetium-99 sestamibi) before repeat parathyroidectomy is sometimes necessary.

Cancer

A serum Ca > 13 mg/dL (> 3.00 mmol/L) suggests some cause of hypercalcemia other than hyperparathyroidism. Urinary Ca excretion is usually normal or high in cancer. In humoral hypercalcemia of cancer, PTH is often decreased or undetectable; PO 4 is often decreased; and metabolic alkalosis, hypochloremia, and hypoalbuminemia are often present. Suppressed PTH differentiates humoral hypercalcemia of cancer from primary hyperparathyroidism. Humoral hypercalcemia of cancer can also be diagnosed by detection of PTH-related peptide in serum.

Multiple myeloma is suggested by simultaneous anemia, azotemia, and hypercalcemia or by the presence of a monoclonal gammopathy. Myeloma is confirmed by bone marrow examination.

FHH

FHH should be considered in patients with hypercalcemia and elevated or high-normal intact PTH levels. FHH is distinguished from primary hyperparathyroidism by the early age of onset, frequent occurrence of hypermagnesemia, and presence of hypercalcemia without hypercalciuria in other family members. The fractional excretion of Ca (ratio of Ca clearance to creatinine clearance) is low (< 1%) in FHH; it is almost always elevated (1 to 4%) in primary hyperparathyroidism. Intact PTH can be elevated or normal, perhaps reflecting altered feedback regulation of the parathyroid glands.

Milk-alkali syndrome

In addition to a history of increased intake of Ca antacids, milk-alkali syndrome is recognized by the combination of hypercalcemia, metabolic alkalosis, and, occasionally, azotemia with hypocalciuria. The diagnosis can be confirmed when the serum Ca concentration rapidly returns to normal when Ca and alkali ingestion stops, although renal insufficiency can persist when nephrocalcinosis is present. Circulating PTH usually is suppressed.

Other causes

In hypercalcemia due to sarcoidosis, other granulomatous disorders, and some lymphomas, serum concentration of 1,25(OH) 2 D may be elevated. Vitamin D toxicity is also characterized by elevated 1,25(OH) 2 D concentration. In other endocrine causes of hypercalcemia, such as thyrotoxicosis and Addison disease, typical laboratory findings of the underlying disorder help establish the diagnosis. When Paget disease is suspected, plain x-rays (see Paget Disease of Bone) are done first and may show characteristic abnormalities.

Laboratory and Clinical Findings in Some Disorders Causing Hypercalcemia

Cause

Findings

Primary hyperparathyroidism

Serum Ca < 12 mg/dL

Ionized serum Ca > 5.2 mg/dL

Low serum PO 4 (particularly with high renal PO 4 excretion)

High alkaline phosphatase (often)

Inappropriately high PTH

Normal or high urinary Ca excretion

No family history of endocrine neoplasia, no neck irradiation during childhood, nor other obvious cause of hyperparathyroidism (typically)

Secondary hyperparathyroidism

Serum Ca < 12 mg/dL

Ionized serum Ca > 5.2 mg/dL

High serum PO 4 (particularly with high renal PO 4 excretion)

High alkaline phosphatase (often)

Inappropriately high PTH

Normal or high urinary Ca excretion

Chronic kidney disease (typically)

Humoral hypercalcemia of cancer

Serum Ca > 12 mg/dL

Low PTH

Normal or low PO 4

Possibly metabolic alkalosis, hypochloremia, and hypoalbuminemia

Familial hypocalciuric hypercalcemia

Ratio of Ca clearance to creatinine clearance of < 1%

Hypermagnesemia (often)

High or normal PTH

Onset at young age

Hypercalcemia without hypercalciuria in patients and family members

Milk-alkali syndrome

No hypercalciuria

Metabolic alkalosis

Azotemia (occasionally)

Low PTH (usually)

Normalization of serum Ca when Ca and alkali ingestion stops

High intake of Ca antacids (typically)

PO 4 = phosphate; PTH = parathyroid hormone.

Treatment

  • Oral PO 4 for serum Ca < 11.5 mg/dL with mild symptoms and no kidney disease

  • IV saline and furosemide for more rapid correction for serum Ca < 18 mg/dL

  • Bisphosphonates or other Ca-lowering drugs for serum Ca < 18 mg/dL and > 11.5 mg/dL or moderate symptoms

  • Hemodialysis for serum Ca > 18 mg/dL

  • Surgical removal for moderate, progressive primary hyperparathyroidism and sometimes for mild disease

  • PO 4 restriction and binders and sometimes calcitriol for secondary hyperparathyroidism

There are 4 main strategies for lowering serum Ca:

  • Decrease intestinal Ca absorption

  • Increase urinary Ca excretion

  • Decrease bone resorption

  • Remove excess Ca through dialysis

The treatment used depends on both the degree and the cause of hypercalcemia.

Mild hypercalcemia

In mild hypercalcemia (serum Ca < 11.5 mg/dL [< 2.88 mmol/L]), in which symptoms are mild, treatment is deferred pending definitive diagnosis. After diagnosis, the underlying disorder is treated. When symptoms are significant, treatment aimed at lowering serum Ca is necessary. Oral PO 4 can be used. When taken with meals, it binds some Ca, preventing its absorption. A starting dose is 250 mg of elemental PO 4 (as Na or K salt) qid. The dose can be increased to 500 mg qid prn unless diarrhea develops. Another treatment is increasing urinary Ca excretion by giving isotonic saline plus a loop diuretic. Initially, 1 to 2 L of saline is given over 2 to 4 h unless significant heart failure is present, because nearly all patients with significant hypercalcemia are hypovolemic. Furosemide 20 to 40 mg IV q 2 to 4 h is given as needed to maintain a urine output of roughly 250 mL/h (monitored hourly). Care must be taken to avoid volume depletion. K and Mg are monitored as often as every 4 h during treatment and replaced IV as needed to avoid hypokalemia and hypomagnesemia. Serum Ca begins to decrease in 2 to 4 h and falls to near-normal within 24 h.

Moderate hypercalcemia

Moderate hypercalcemia (serum Ca > 11.5 mg/dL [< 2.88 mmol/L] and < 18 mg/dL [< 4.51 mmol/L]) can be treated with isotonic saline and a loop diuretic as is done for mild hypercalcemia or, depending on its cause, agents that decrease bone resorption (usually bisphosphonates, calcitonin, or infrequently plicamycin or gallium nitrate), corticosteroids, or chloroquine.

Bisphosphonates inhibit osteoclasts. They are usually the drugs of choice for cancer-associated hypercalcemia. Pamidronate can be given for cancer-associated hypercalcemia as a one-time dose of 30 to 90 mg IV, repeated only after 7 days. It lowers serum Ca for 2 wk. Zoledronate can also be given in doses of 4 to 8 mg IV and lowers serum Ca very effectively for an average of > 40 days. Ibandronate 4 to 6 mg IV can be given for cancer-associated hypercalcemia; it is effective for about 14 days. Etidronate 7.5 mg/kg IV once/day for 3 to 5 days is used to treat Paget disease and cancer-associated hypercalcemia. Maintenance dosage is 20 mg/kg po once/day, but the dose must be reduced when GFR is low. Repetitive use of IV bisphosphonates to treat hypercalcemia associated with metastatic bone disease or myeloma has been associated with osteonecrosis of the jaw. Some reports suggest this finding may be more common with zoledronate. Renal toxicity has been reported in patients receiving zoledronate. Oral bisphosphonates (eg, alendronate or risedronate) can be given to maintain Ca in the normal range but are not generally used for treating hypercalcemia acutely.

Calcitonin (thyrocalcitonin) is a rapidly acting peptide hormone normally secreted in response to hypercalcemia by the C cells of the thyroid. Calcitonin appears to lower serum Ca by inhibiting osteoclastic activity. A dosage of 4 to 8 IU/kg sc q 12 h of salmon calcitonin is safe. Its usefulness in the treatment of cancer-associated hypercalcemia is limited by its short duration of action with the development of tachyphylaxis (often after about 48 h) and by the lack of response in 40% of patients. However, the combination of salmon calcitonin and prednisone may control serum Ca for several months in some patients with cancer. If calcitonin stops working, it can be stopped for 2 days (while prednisone is continued) and then resumed.

Corticosteroids (eg, prednisone 20 to 40 mg po once/day) can help control hypercalcemia as adjunctive therapy by decreasing calcitriol production and thus intestinal Ca absorption in most patients with vitamin D toxicity, idiopathic hypercalcemia of infancy, and sarcoidosis. Some patients with myeloma, lymphoma, leukemia, or metastatic cancer require 40 to 60 mg of prednisone once/day. However, > 50% of such patients fail to respond to corticosteroids, and response, when it occurs, takes several days; thus, other treatment usually is necessary.

Chloroquine PO 4 500 mg po once/day inhibits 1,25(OH) 2 D synthesis and reduces serum Ca concentration in patients with sarcoidosis. Routine ophthalmologic surveillance (eg, retinal examinations every 6 to 12 mo) is mandatory to detect dose-related retinal damage.

Plicamycin 25 μg/kg IV once/day in 50 mL of 5% D/W over 4 to 6 h is effective in patients with hypercalcemia due to cancer but is rarely used because other treatments are safer.

Gallium nitrate is also effective in hypercalcemia due to cancer but is used infrequently because of renal toxicity and limited clinical experience.

Severe hypercalcemia

In severe hypercalcemia (serum Ca > 18 mg/dL [> 4.50 mmol/L] or with severe symptoms), hemodialysis with low-Ca dialysate may be needed in addition to other treatments. Although there is no completely satisfactory way to correct severe hypercalcemia in patients with renal failure, hemodialysis is probably the safest and most reliable short-term treatment.

IV PO 4 (disodium PO 4 or monopotassium PO 4 ) should be used only when hypercalcemia is life threatening and unresponsive to other methods and when short-term hemodialysis is not possible. No more than 1 g should be given IV in 24 h; usually 1 or 2 doses over 2 days lower serum Ca for 10 to 15 days. Soft-tissue calcification and acute renal failure may result. (N ote: IV infusion of Na sulfate is even more hazardous and less effective than PO 4 infusion and should not be used.)

Hyperparathyroidism

Treatment for hyperparathyroidism depends on severity.

Patients with asymptomatic primary hyperparathyroidism with no indications for surgery may be treated conservatively with methods to ensure that serum Ca concentrations remain low. Patients should remain active (ie, avoid immobilization that could exacerbate hypercalcemia), follow a low-Ca diet, drink plenty of fluids to minimize the chance of nephrolithiasis, and avoid drugs that can raise serum Ca, such as thiazide diuretics. Serum Ca and renal function are monitored every 6 mo. Bone density is monitored every 12 mo. However, subclinical bone disease, hypertension, and longevity are concerns. Osteoporosis is treated with bisphosphonates.

Surgery is indicated for patients with symptomatic or progressive hypoparathyroidism. The indications for surgery in patients with asymptomatic, primary hyperparathyroidism are controversial. Surgical parathyroidectomy increases bone density and may have modest effects on some quality of life symptoms, but most patients do not have progressive deterioration in biochemical abnormalities or bone density. Still, concerns about hypertension and longevity remain. Many experts recommend surgery in the following circumstances:

  • Serum Ca 1 mg/dL (0.25 mmol/L) greater than the upper limits of normal

  • Calciuria > 400 mg/day (> 10 mmol/day)

  • Creatinine clearance 30% less than that of age-matched controls

  • Peak bone density at the hip, lumbar spine, or radius 2.5 standard deviations below controls (T score =2.5)

  • Age < 50 yr

  • The possibility of poor adherence with follow-up

Surgery consists of removal of adenomatous glands. PTH concentration can be measured before and after removal of the presumed abnormal gland using rapid assays. A fall of 50% or more 10 min after removal of the adenoma indicates successful treatment. In patients with disease of > 1 gland, several glands are removed, and often a small portion of a normal-appearing parathyroid gland is reimplanted in the belly of the sternocleidomastoid muscle or subcutaneously in the forearm to prevent hypoparathyroidism. Parathyroid tissue is also occasionally preserved using cryopreservation to allow for later autologous transplantation in case persistent hypoparathyroidism develops.

When hyperparathyroidism is mild, the serum Ca concentration drops to just below normal within 24 to 48 h after surgery; serum Ca must be monitored. In patients with severe osteitis fibrosa cystica, prolonged, symptomatic hypocalcemia may occur postoperatively unless 10 to 20 g elemental Ca is given in the days before surgery. Even with preoperative Ca administration, large doses of Ca and vitamin D may be required (see Hypocalcemia : Treatment) while bone Ca is repleted.

Hyperparathyroidism in renal failure is usually secondary. Measures used for treatment can also be used for prevention. One aim is to prevent hyperphosphatemia. Treatment combines dietary PO 4 restriction and PO 4 binding agents, such as Ca carbonate or sevelamer. Despite the use of PO 4 binders, dietary restriction of PO 4 is needed. Aluminum-containing compounds have been used to limit PO 4 concentration, but they should be avoided, especially in patients receiving long-term dialysis, to prevent aluminum accumulation in bone resulting in severe osteomalacia. Vitamin D administration is potentially hazardous in renal failure because it can increase PO 4 absorption and contribute to hypercalcemia; administration requires frequent monitoring of Ca and PO 4 . Treatment should be limited to patients with any of the following:

  • Symptomatic osteomalacia (unrelated to aluminum)

  • Secondary hyperparathyroidism

  • Postparathyroidectomy hypocalcemia

Although oral calcitriol is often given along with oral Ca to suppress secondary hyperparathyroidism, the results are variable in patients with end-stage renal disease. The parenteral form of calcitriol, or vitamin D analogs such as paricalcitol, may better prevent secondary hyperparathyroidism in such patients, because the higher attained serum concentration of 1,25(OH) 2 D directly suppresses PTH release. Simple osteomalacia may respond to calcitriol 0.25 to 0.5 mcg po once/day, whereas correction of postparathyroidectomy hypocalcemia may require prolonged administration of as much as 2 mcg of calcitriol po once/day and 2 g of elemental Ca/day. The calcimimetic, cinacalcet, modulates the set point of the Ca-sensing receptor on parathyroid cells and decreases PTH concentration in dialysis patients without increasing serum Ca. In patients with osteomalacia caused by having taken large amounts of aluminum-containing PO 4 binders, removal of aluminum with deferoxamine is necessary before calcitriol administration reduces bone lesions.

FHH

Although FHH results from histologically abnormal parathyroid tissue, the response to subtotal parathyroidectomy is unsatisfactory. Because overt clinical manifestations are rare, drug therapy is not routinely indicated.

Key Points

  • The most common causes of hypercalcemia are hyperparathyroidism and cancer.

  • Clinical features include polyuria, constipation, anorexia, and hypercalciuria with renal stones; patients with high Ca concentrations may have muscle weakness, confusion, and coma.

  • Do chest x-ray; measure electrolytes, BUN, creatinine, ionized Ca, PO 4 , PTH, and alkaline phosphatase, and do serum protein immunoelectrophoresis.

  • In addition to treating the cause, treat mild hypercalcemia (serum Ca < 11.5 mg/dL [< 2.88 mmol/L]) with oral PO 4 or isotonic saline plus a loop diuretic.

  • For moderate hypercalcemia (serum Ca > 11.5 mg/dL [< 2.88 mmol/L] and < 18 mg/dL [< 4.51 mmol/L]), add a bisphosphonate, corticosteroids and sometimes calcitonin.

  • For severe hypercalcemia, hemodialysis may be needed.

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Drugs Mentioned In This Article

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  • AREDIA
  • ELIXOPHYLLIN
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  • ROCALTROL
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  • ARALEN
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