A 52-yrs-old woman sees her physician with compl-aints of fatigue, headache, flank pain, hematuria, and abdominal pain. Which is most suggestive of her diagnosis?
|A||Serum acid phosphatase above 120 IU/L|
|B||Serum alkaline phosphatase above 120 IU/L|
|C||Serum calcium above 11 mg/dL|
|D||Urinary calcium below 100 mg/day|
a. Resorptive hypercalciuria is an infrequent abnormality most commonly associated with primary hyperparathyroidism.
b. Primary hyperparathyroidism is the cause of nephrolithiasis in about 5% of cases.
c. Excessive PTH secretion from a parathyroid adenoma leads to excessive bone resorption and increased renal synthesis of 1,25(OH)2D3, which in turn enhances intestinal absorption of calcium; the net effect is elevated serum and urine calcium levels and reduced serum phosphorus levels.
d. Administration of a thiazide diuretic will enhance renal calcium reabsorption and exacerbate the hypercalcemia, thereby facilitating the diagnosis (“thiazide challenge”).
e. When diagnosing primary hyperparathyroidism, other causes of hypercalcemia should be excluded.
f. The diagnosis should be suspected in patients with nephrolithiasis and serum calcium levels greater than 10.1 mg/dL.
g. Patients with mild hyperparathyroidism may exhibit relatively small increases of serum calcium . as such, repeated measurements of serum calcium may be necessary to make the diagnosis.
h. Measurement of serum ionized calcium may help in equivocal cases, because it may be elevated in the setting of normal serum calcium .
i. Urinary cyclic AMP levels have been used to diagnose primary hyperparathyroidism, because PTH promotes release of cyclic AMP from the kidney, leading to increased urinary cyclic AMP levels .