Page 155 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

Disorders of Calcium: Hypercalcemia and Hypocalcemia 145

Normocalcemic uremia
20 Hypercalcemic uremia 20

* *
15 15
*
mg/dL 10 * * 10 mg/dL

5 5

0 0
Calcium Creatinine Phosphorus

600 ** 40
*

30
400
pg/mL * 20 pg/mL

* *
200 8 8.5 9
10

0 0
PTH Age (yrs) Calcitriol
Figure 6-12 Comparison of biochemical data for dogs with renal failure and hypercalcemia or
normocalcemia. Dogs with renal failure were normalized for age and had similar concentrations of serum
creatinine, phosphorus, and calcitriol. Serum concentrations of PTH were greater in the hypercalcemic dogs
than in the normocalcemic dogs. Data are mean SEM. For normal and hypercalcemic uremic dogs, n ¼ 10;
*
**
for normocalcemic uremic dogs, n ¼ 20. Significant differences were P <.0001 (from normal) and P <.02
(from normocalcemic uremia PTH) by Student t test. (From Nagode LA, Steinmeyer CL, Chew DJ, et al.
Hyper- and normo-calcemic dogs with chronic renal failure: relations of serum PTH and calcitriol to
parathyroid gland Ca þþ set-point. In: Norman AW, Schaefer K, Grigoleit HG, et al, editors. Vitamin D 1988.
Chemical, biochemical and clinical endocrinology. Berlin: Walter de Gruyter & Co, 1988: 799–800.)

phosphorus and low or undetectable PTH concentrations.
Serum calcium returned to normal, and PTH and phos- Humoral forms Local forms
phorus increased with the feeding of a maintenance diet. 29
PATHOLOGIC OR CONSEQUENTIAL ++ ++ Solid tumors or
HYPERCALCEMIA Ca Ca multiple myeloma
Cancer-Associated Hypercalcemia
The most common cause of hypercalcemia in dogs is can- Humoral
Tumor
cer-associated hypercalcemia. Cancer is third in frequency factors Hematologic
of association with hypercalcemia in cats. There are three Ca ++ Ca ++ tumors
mechanisms (Fig. 6-13) of increased serum calcium con-
centration induced by neoplasms: (1) HHM, (2) hyper- Figure 6-13 Pathogenesis of cancer-associated hypercalcemia.
calcemia induced by metastases of solid tumors to bone Humoral and local forms of cancer-associated hypercalcemia
(local osteolytic hypercalcemia [LOH]), and (3) hemato- increase circulating concentrations of calcium by stimulation of
logic malignancies growing in the bone marrow osteoclastic bone resorption and increased renal tubular
(LOH). 479,480 reabsorption of calcium.