Lesson 71 - Clinical Calcium Considerations and Parathyroid Diseases

A 7-year-old male neutered Chow is presented for PU/PD, halitosis, and weight loss. Bloodwork identifies a hypercalcemia and iPTHis measured and returns within the normal range. What is the diagnosis?

Primary hyperparathyroidism

3 multiple choice options

What effects does PTH have on the bones and kidneys?

1. increased bone resorption

2. increased calcium absorption in the kidneys

3. increased phosphorus excretion in the kidneys

What is the net effect of PTH on serum calcium?

increase

What is the net effect of PTH on serum phosphorus?

decrease

What effects does calcitonin have on the bones and kidneys?

1. decreased bone resorption

2. decrease calcium reabsorption in the kidneys

3. decrease phosphorus reabsorption in the kidneys

What is the net effect of calcitonin on serum calcium?

decrease

What is the net effect of calcitonin on serum phosphorus?

increase

What effects does vitamin D3 have on the bones, kidneys, and intestines?

1. maintains calcium transport in bone

2. increase calcium reabsorption in the kidneys

3. increase calcium and phosphorus absorption in the intestines

What is the net effect of vitamin D3 on serum calcium?

increase

What is the net effect of vitamin D3 on serum phosphorus?

increase

What are the three forms of calcium?

1. ionized (50%)

2. bound (40%)

3. complexed (10%)

What is the best representation of free calcium?

ionized

What is 40% of calcium bound to?

albumin

What are the components of complexed calcium?

phosphate, citrate, sulfate, lactate, bicarbonate

What is involved in calcium homeostasis?

1. parathormone

2. calcitonin

3. vitamin D

Where does parathormone come from?

chief cells in PTH gland

What stimulates the release of parathormone?

low calcium

Where does calcitonin come from?

c-cells in thyroid

What stimulates the release of calcitonin?

high calcium

What are the forms of vitamin D involved in calcium homeostasis?

1. Cholecalciferol (dietary vitamin D3)

2. 25-hydroxycholcalciferol from the liver

3. 1,25 dihydroxycholecalciferol (kidney, active vitamin D3, calcitriol)

Which calcium condition would have low calcium and low PTH?

primary hypoparathyroidism

Which calcium condition would have low calcium and high PTH?

secondary nutritional/renal hyperparathyroidism

Which calcium condition would have high calcium and low PTH?

hypercalcemia of malignancy

Which calcium condition would have high calcium and high PTH?

primary hyperparathyroidism

What are the clinical signs of hypocalcemia?

1. Muscle fasciculations/tension/twitches/tremors

2. Seizures

3. Pawing at face "itchy face"

4. Nervousness

5. Disorientation

6. Ataxia

7. Fever

8. Weak pulses

9. Panting

What are the rule-outs for hypocalcemia?

1. Hypoparathyroidism, hypovitaminosis D (via GI dz)

2. Ecclampsia

3. Renal disease

4. Pancreatitis/Phosphates (enemas)

5. Ethylene glycol toxicity

6. Spurious/sepsis

What are the musculoskeletal clinical signs of hypercalcemia?

muscle weakness, exercise intolerance, muscle wasting, twitching

What are the GI clinical signs of hypercalcemia?

prolonged GI transit, constipation, inappetence, +/- GI bleeds

What are the renal clinical signs of hypercalcemia?

PU/PD, ischemic renal damage/failure, soft tissue calcification, urolithiasis

What are the cardiovascular clinical signs of hypercalcemia?

increased myocardial contractility, shortened systole, decreased automaticity

What are the rule-outs for hypercalcemia?

1. Granulomatous disease

2. Osteopathy/osteolytic disease

3. Spurious

4. Hyperparathyroidism

5. Hypervitaminosis D

6. Addisons

7. Renal Disease

8. Neoplasia (LSA, ASA, MM)

9. Idiopathic (cats)

10. Temperature (cats)

How is hypercalcemia treated?

1. fluid therapy

2. furosemide

3. short term glucocorticoids

4. bisphosphonates

5. mithramycin

6. calcimimetics (cinacalcet)

7. calcitonin

Why is treatment of hypercalcemia with glucocorticoids not a good idea when neoplasia is expected?

can obscure the definitive diagnosis

Which hypercalcemia treatments can only be used if the patient is hydrated?

1. furosemide

2. bisphosphonates

What percentage of cats with idiopathic hypercalcemia are asymptomatic?

50%

What percentage of cats with idiopathic hypercalcemia present with anorexia and lethargy?

70%

What are the clinical signs of idiopathic hypercalcemia of felines?

1. anorexia and lethargy

2. vomiting/diarrhea

3. constipation

4. PU/PD

5. weakness

6. twitching

7. seizures

8. secondary urolithiasis (pollakiuria, hematuria, stranguria)

What form of calcium should you measure for idiopathic hypercalcemia of felines?

ionized

What will PTH be with idiopathic hypercalcemia of felines?

low or undetectable

What is the treatment for idiopathic hypercalcemia of felines?

1. General therapeutics for an acute emergency

2. Alendronate (bisphosphonate) for chronic

3. Canned, high fiber, prescription renal, high protein/low carb diets

How should treatment of hypercalcemia be monitored?

ionized calcium evaluation every 3-4 weeks

How long can it take before dietary therapy efficacy can be identified?

2-3 months

What is the prognosis for hypercalcemia?

slowly progressive, many remain asymptomatic for a long time

What are the complications of uncontrolled hypercalcemia?

renal failure, urolithiaisis, cardiac arrhythmias, UTIs, GI disease, and neuromuscular disorders

What are the types of hyperparathyroidism?

1. primary

2. secondary

3. tertiary

What are the causes of primary hyperparathyroidism?

1. benign adenoma most common

2. hyperplasia rare

What are the causes of secondary hyperparathyroidism?

1. Nutritional

2. Renal

3. Intestinal

What are the causes of tertiary hyperparathyroidism?

receptor abnormalities

What are the clinical signs of hyperparathyroidism?

1. PU/PD

2. Lethargy

3. Incontinence

4. Weakness/exercise intolerance

5. Anorexia

6. Muscle wasting

7. Vomiting

8. Constipation

9. Could be NONE!

10. Urinary tract disease (Ca++ urolithiasis)

How is hyperparathyroidism diagnosed?

1. elevated PTH with elevated calcium (but PTH could be normal)

2. osteopenia and urolithiasis on radiography

3. one atrophied thyroid gland seen on ultrasound

Why could PTH be normal in hyperparathyroidism?

negative feedback

What is the treatment for hyperparathyroidism?

1. surgical excision of tumor and uroliths

2. medical management with bisphosponates and calcimimetics

3. Initiate calcitriol therapy the day of or one day before surgery

4. Oral calcium supplementation

What is the post-op management of surgical excision of a hyperparathyroid causing tumor?

1. Monitor patient for hypocalcemia Q2-4 hours

2. Measure Ca++ and watch for behavior changes and muscle fasciculations (Itchy face!)

3. Treat with IV calcium gluconate 5-15 m/kg and monitor ECG if hypocalcemic

What is seen with renal secondary hyperparathyroidism?

1. Chronic Kidney Disease

2. Low calcium and high phosphorus triggers elevated PTH

3. Demineralized bone

What is the treatment for renal secondary hyperparathyroidism?

1. Treat CKD

2. Ensure normal Ca++/Phos product

3. Calcitriol therapy only if phosphorus is <6

What are the forms of nutritional secondary hyperparathyroidism?

intestinal and dietary

What are the causes of intestinal nutritional secondary hyperparathyroidism?

1. Intestinal malabsorption (fat malabsorption)

2. Diarrhea

What is the treatment for intestinal nutritional secondary hyperparathyroidism?

1. correct primary disease

2. calcitriol

What are the causes of dietary nutritional secondary hyperparathyroidism?

1. Inappropriate Ca++/Phos ratio in diet

2. Low calcium

3. Low Vitamin D

What are the clinical signs of dietary nutritional secondary hyperparathyroidism?

lameness, loose teeth, swollen maxilla, pathologic fractures

What is the cause of hypoparathyroidism?

immune mediated destruction of parathyroids (lymphocytic parathyroiditis)

What are the clinical signs of hypoparathyroidism?

1. Related to hypocalcemia

2. Muscle fasciculation and cramps

3. Seizures

4. Itchiness, pawing at the face

5. Cataracts

6. Diaphragm contractions concurrent with heartbeat

How is hypoparathyroidism diagnosed?

1. Decreased total and ionized Ca++

2. Increased Phosphorus

3. Decreased iPTH

How is hypoparathyroidism treated?

1. IV calcium for emergency stabilization

2. Oral Calcitriol

3. Oral Calcium supplements if needed