Parathyroid Disease

Question 1

Calcium regulation
1. Parathyroid hormone - made by _______
2. Calcitriol (activated vit D) - activated in the ______
3. Calcitonin - made by the ______

Answer 1

PTH - parathyroid glands
Calcitriol - kidney activates
Calcitonin - thyroid

Question 2

PTH is made by the ____ cells of the parathyroid glands.

Answer 2

Chief

Question 3

PTH action:

Answer 3

Maintain plasma ionized calcium
Regulate plasma phosphorus

Question 4

PTH targets (3)

Answer 4

Bone - increases release/blood levels of calcium and phosphorus

Kidney - Increase calcium resorption; increase phosphorus excretion

Small intestines - indirectly via increase in calcitriol -> increased calcium and phosphorus

Question 5

Targets of calcitriol

Answer 5

Small intestine - increases formation of calcium binding protein which transports calcium from the lumen into the intestinal epithelial cells

Bone - LG amt = stimulates bone resorption -> inc. Ca and P; SM amt causes bone calcification

Parathyroid glands - negative feedback leads to decreased PTH

Question 6

Calcitonin is made in the _____ cells of the thyroid.

Answer 6

Parafollicular / C cells

Question 7

What is the function of calcitonin?

Answer 7

Decrease serum calcium concentration

Opposite effects of PTH
- bone: decreases osteocyte membrane activity and osteoclast formation; much less significant than PTH

Question 8

Differentials for Hypercalcemia

Answer 8

H - Hyperparathyroidism (primary)
O - Osteolytic
G - Granulomatous disease
S - Spurious

I - Idiopathic (cats), iatrogenic (meds, supplements)
N - Neoplasia

Y - Young
A - Addison’s (HYPOadrenocorticism)
R - Renal disease
D - Vitamin D toxicosis

Question 9

Define primary hyperparathyroidism (PHP)

Answer 9

Excessive production of PTH by the parathyroid glands.

Caused by:
- adenoma
- carcinoma
- hyperplasia

*can affect one or more glands

Question 10

Primary hyperparathyroidism signalment

Answer 10

Middle age - older
Breeds: Keeshond, labs, goldens, GSD

Question 11

Clinical signs of hyperparathyroidism

Answer 11

• unlike other causes of hypercalcemia, dogs with PHP are not usually clinical; other causes of hypercalcemia generally result in a sick to very sick dog
• If present: PUPD, lethargy/weakness, urinary signs - infections, calculi (calcium oxalate)
• long standing hypercalcemia can lead to renal failure due to renal vasoconstriction leading to GFR and renal blood flow

Question 12

An older, apparently healthy dog with hypercalcemia is more than likely going to have ______.

Answer 12

Primary hyperparathyroidism

Question 13

Describe the minimum database for a dog with primary hyperparathyroidism.

Answer 13

CBC - usually normal, may have mild anemia

CHEM - Hypercalcemia (100% of cases); low-normal phosphorus

UA - UTI, evidence of calculi, Isosthenuria or hyposthenuria

Question 14

Diagnostics for primary hyperparathyroidism

Answer 14

Malignancy panel
- ionized calcium, PTH, PTH related peptide
- elevated iCa with inapp. Normal PTH = consistent with hyperPTH
- PTHrp produced by some neoplasias but absence does not rule out

Imaging
- Abdominal rads/US/CT: nephroliths, cystic calculi
- Thoracid rads/CT: Mets
- Cervical US/CT: thyroid mass, parathyroid mass (difficult)

Question 15

Treatment for severe hypercalcemia with hyperparathyroidism

Answer 15

Fluid therapy: physiologic saline diuresis

Enhance renal calcium excretion
- furosemide
- glucocorticoids
- calcitonin

Inhibit bone resorption
- bisphosphonates
- glucocorticoids
- calcitonin

Suppress PTH release
- Cinacalcet

Question 16

Treatment for mild/not clinical hypercalcemia with hyperparathyroidism

Answer 16

Monitor values

Question 17

Treatment options for hypercalcemia associated with hyperparathyroidism

Answer 17

Medical
- furosemide, glucocorticoids, calcitonin, bisphosphonates, Cinacalcet

Surgical - removal of affected gland(s); hypocalcemia can occur until glands recover -> short term calcitriol and calcium carbonate supplementation

Radiofrequency heat / ethanol ablation

Question 18

Differentials for Hypocalcemia

Answer 18

P = phosphate enemas
E = eclampsia
A = albumin decrease
C = chronic renal disease
E = ethylene glycol tox/acute kidney injury

P = PTH deficiency
A = acute panky
I = intestinal malabsorption
N = Nutritional (vit D deficiency)

Plus many more

Question 19

Signalment for Hypoparathyroidism

Answer 19

More dogs
More females
~ 5 yrs old
Poodles, Mini Schnauzers, GSD, Labrador Retrievers, Terriers

Question 20

What is hypoparathyroidism?

Answer 20

Cessation of parathyroid function - decreased secretion of PTH

Decrease in serum calcium and increase in phosphorus

Question 21

Causes of hypoparathyroidism

Answer 21

1. Suppressed secretion of PTH without destruction (trauma, surgery)
2. Atrophy - sudden correction of chronic hypercalcemia
3. Iatrogenic - removal of parathyroid glands during thyroidectomy
4. Idiopathic, “Primary” - immune mediated destruction

Question 22

Clinical signs of hypoparathyroidism

Answer 22

Signs often present suddenly, but true course of disease is gradual in onset

Seizures
Intense facial rubbing/biting or licking paws
Tetany/muscle spasms
Tense/nervous
Stilted gait
Lethargy, weakness, anorexia
Vomiting, diarrhea, fever
Cataracts
Growling
Cardiac abnormalities

Question 23

Seen on physical exam with hypoparathyroidism

Answer 23

Changes mostly related to hypocalcemia:
- muscle fasciculations
- seizures during exam
- cardiac abnormalities may be seen (tachyarrhythmias, muffled heart sounds, weak pulses)

Question 24

Diagnostics for hypoparathyroidism

Answer 24

Clinical signs with decreased serum calcium
Rule out other differentials = PEACE PAIN
Increased serum phosphorus
Decreased ionized calcium
Low PTH and calcitriol (MIchigan State test)

Question 25

Treatment for hypoparathyroidism

Answer 25

Treatment will be lifelong

Emergency Therapy
- IV calcium gluconate given slowly IV

Chronic
- calcitriol (usually lifelong)
- calcium carbonate (can taper)

Question 26

Monitoring of hypoparathyroidism

Answer 26

Frequent rechecks of ionized calcium as every animal responds differently to calcitriol - dose adjustment needed

Goal
- low normal/slightly low calcium levels
- avoid hypercalcemia due to risk of renal failure and other complications