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Zorluk: OrtaInterpreting Laboratory Results

Match the following serum calcium, phosphate, and intact parathyroid hormone (PTH) laboratory profiles to their most appropriate underlying diagnosis. (Reference ranges: Calcium 8.4−10.28.4 - 10.2 mg/dL, Phosphate 2.7−4.52.7 - 4.5 mg/dL, Intact PTH 15−6515 - 65 pg/mL)

  • Calcium: 11.211.2 mg/dL, Phosphate: 2.12.1 mg/dL, Intact PTH: 120120 pg/mLPrimary hyperparathyroidism
  • Calcium: 7.67.6 mg/dL, Phosphate: 5.85.8 mg/dL, Intact PTH: 250250 pg/mLSecondary hyperparathyroidism (chronic kidney disease)
  • Calcium: 7.57.5 mg/dL, Phosphate: 5.25.2 mg/dL, Intact PTH: 88 pg/mLHypoparathyroidism
  • Calcium: 8.08.0 mg/dL, Phosphate: 2.22.2 mg/dL, Intact PTH: 140140 pg/mLSevere vitamin D deficiency (Osteomalacia)

Cevap

Profile 1 matches Primary hyperparathyroidism; Profile 2 matches Secondary hyperparathyroidism (chronic kidney disease); Profile 3 matches Hypoparathyroidism; Profile 4 matches Severe vitamin D deficiency (Osteomalacia).
The correct matches require systematic evaluation of calcium and phosphate in the context of the PTH response. Primary parathyroid overactivity directly causes hypercalcemia and hypophosphatemia. Renal failure causes phosphate retention and poor calcitriol synthesis, leading to hypocalcemia and a compensatory rise in PTH. Primary parathyroid failure drops PTH, causing both hypocalcemia and hyperphosphatemia. Vitamin D deficiency causes poor absorption of both calcium and phosphate, driving PTH up, which further depletes phosphate.

Adım Adım Çözüm

1
Evaluate the first profile (Calcium: 11.2, Phosphate: 2.1, PTH: 120).
The patient has hypercalcemia, hypophosphatemia, and elevated PTH.
An elevated PTH in the setting of hypercalcemia indicates primary hyperparathyroidism, as PTH is autonomously secreted and driving the calcium up while wasting phosphate.
2
Evaluate the second profile (Calcium: 7.6, Phosphate: 5.8, PTH: 250).
The patient has hypocalcemia, hyperphosphatemia, and markedly elevated PTH.
Hyperphosphatemia binds calcium leading to hypocalcemia, which strongly stimulates PTH release. This is the classic pattern of secondary hyperparathyroidism seen in chronic kidney disease due to failure to excrete phosphate.
3
Evaluate the third profile (Calcium: 7.5, Phosphate: 5.2, PTH: 8).
The patient has hypocalcemia, hyperphosphatemia, and low PTH.
A low PTH in the setting of hypocalcemia points to an inability of the parathyroid glands to produce hormone (hypoparathyroidism), leading to lack of calcium reabsorption and lack of phosphate excretion.
4
Evaluate the fourth profile (Calcium: 8.0, Phosphate: 2.2, PTH: 140).
The patient has hypocalcemia, hypophosphatemia, and elevated PTH.
Poor absorption of calcium and phosphate from the gut characterizes vitamin D deficiency. The resulting hypocalcemia appropriately stimulates PTH, which normalizes calcium slightly but causes further renal wasting of phosphate.

Anahtar Kavram

Differentiating disorders of calcium and phosphate metabolism using intact PTH levels.
Tahmini Süre:1m 30s
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Interpreting Laboratory Results

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