Laboratory Findings in Calcium Disorders
| Ca | PTH | Disease | PO4 | 25-(OH)D | 1,25-(OH),D |
|---|
| up | upup | Hyperparathyroidism (1° and 3°) | down | down to normal | normal to up |
| up | up or normal | Familial hypocalciuric hypercalcemia | down | var. | nl |
| up | down | Malignancy | var | var | var. |
| up | down | Vitamin D excess | up | up | normal to up |
| up | dwon | Milk-alkali syndrome.thiazides | var | var. | var. |
| up | down | Bone turnover | normal to up | var | nl |
| ------ | -------------- | -------------------------------------- | -------------- | ---------------- | ---------------- |
| down | upup | Pseudohypoparathyroidism | up | var | down |
| down | up | Vitamin D deficiency | down | down down | normal to down |
| down | up | Chronic renal failure (2° hyperpara) | normal to up | var | down |
| down | var | Acute calcium sequestration | var | var | var |
| down | down | Hypoparathyroidism | up | var | down to normal |
Pitfalls in measuring calcium
- 生理活性鈣是游離的或電離的 (ICa)。
- Serum Ca reflects total calcium (bound + unbound) and ∴ influenced by albumin (main Ca-binding protein).
- 血清 Ca 反映總鈣（結合 + 未結合）和 所以：受白蛋白（主要 Ca 結合蛋白）的影響。
- Corrected Ca (mg/dL) = measured Ca (mg/dL) + {0.8 × [4 – albumin (g/dL)]}
- 鹼中毒會導致更多的Ca與白蛋白結合（∴總Ca可能正常但↓ICa）Alkalosis will cause more Ca to be bound to albumin (∴ total Ca may be normal but ↓ ICa)
- 最好直接測量 Ca++（但準確度取決於實驗室） Best to measure ionized Ca directly (but accuracy is lab dependent)
