2. Calcium
• 99% of the bodies calcium is in the bone in
calcium phosphate compounds
3. Calcium
• Calcium ions serve many important roles in the
body.
• Components of bone and teeth
• Responsible for the excitation and contraction of
muscle cells
• Important is regulating cardiac function
• Required for nerve function
• Activates metabolic enzymes
• Serves as a cofactor for several blood-clotting
proteins
5. Ionized Calcium
• Ionized calcium is considered the biologically
active form of calcium and is the component that
regulates the secretion of PTH.
• Total calcium is made up of three components
:protein bound calcium, ionized calcium and
calcium that is complexed with other anions
such as phosphate, citrate, bicarbonate and
lactate
7. Parathyroid Hormone
PTH
• Parathyroid glands are found in all air-breathing
vertebrates
• The parathyroid glands act to increase serum
calcium via production of parathyroid hormone
(PTH).
• Parathyroid gland cells have receptors for
ionized Calcium that regulate secretion of PTH
in a tight negative-feedback relation.
• Small increases in ionized calcium inhibit
secretion of PTH and small decreases of ionized
calcium prompt the release of PTH
8. PTH
Parathyroid Hormone
• The primary function of PTH is to elevate the
serum ionized Ca++ concentration.
• This is accomplished by
• 1. Stimulating bone resorption (dissolution)
• 2. Increase the Reabsorption of Ca++ in the
kidneys
• 3. Decrease renal Phosphate reabsorbtion
• 4. Stimulate activation of Vit D in the kidneys
• Vit D increases the efficiency of Ca++
absorption in the small intestine
9. Hypercalcemia
• Calcium is intimately involved with muscle
and nerve function
• The biologically active form of calcium is
the ionized portion
• Ionized calcium has a negative feedback
on parathyroid hormone (PTH) production
• Normal total blood calcium levels are
10mg/dl
• Clinical signs appear around 15mg/dl
10. Hypercalcemia
Symptoms
• Often related to underlying disease
• Lethargy
• Weakness
• PU/PD
• Cardiac irregularities
• Anorexia
• +/- seizures and muscle twitching
11. Hypercalcemia
Etiology
• Laboratory error
• Hypercalcemia of malignancy
• Addison’s disease (30-40%)
• Primary hyperparathyroidism
• Granulomatous disease (Blasto, Cocci)
• Cholecalciferol rodenticide poisoning
• Bone cancer
• Bone infection (osteomyelitis)
12. Parathyroid Hormone
Analysis
• Measurement of PTH currently is
accomplished using commercially
available immunoradiometric assays
(IRMAs) for human PTH.
• PTH degrades quickly . Samples are
usually frozen. Large commercial labs
and the University of Michigan can run the
analysis
14. Hypercalcemia
Malignant Causes
• >40% of all cases of hypercalcemia in dogs and
<30% in cats are caused by malignant tumors.
• Humoral Hypercalcemia of Malignancy (HHM)-
Parathyroid hormone related protein. (PTHrP)
• 1. Lymphosarcoma (especially medianstinal
forms)
• 2. Adenocarcinoma of the anal sacs
• 3. Multiple Myeloma
19. Hypocalcemia
• A common biochemical abnormality in
dogs and cats caused by numerous
conditions. Common conditions
associated with Hypocalcemia are
puerperal tetany, iatrogenic
hypoparathyroidism and primary
hypoparathyroidism
21. Hypocalcemia
Symptoms
• Tetany, Stiff gait, muscle fasciculations and
generalized tremors
• Facial rubbing and pawing
• Generalized seizures
• Drooling (cats)
• Hyperthermia**
• Panting and Hyperventilation**
• Puerperal tetany usually occurs postpartum
but can occur near the end of pregnancy
