Parathyroid Disease Flashcards
Calcium regulation
1. Parathyroid hormone - made by _______
2. Calcitriol (activated vit D) - activated in the ______
3. Calcitonin - made by the ______
PTH - parathyroid glands
Calcitriol - kidney activates
Calcitonin - thyroid
PTH is made by the ____ cells of the parathyroid glands.
Chief
PTH action:
Maintain plasma ionized calcium
Regulate plasma phosphorus
PTH targets (3)
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
Targets of calcitriol
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
Calcitonin is made in the _____ cells of the thyroid.
Parafollicular / C cells
What is the function of calcitonin?
Decrease serum calcium concentration
Opposite effects of PTH
- bone: decreases osteocyte membrane activity and osteoclast formation; much less significant than PTH
Differentials for Hypercalcemia
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
Define primary hyperparathyroidism (PHP)
Excessive production of PTH by the parathyroid glands.
Caused by:
- adenoma
- carcinoma
- hyperplasia
*can affect one or more glands
Primary hyperparathyroidism signalment
Middle age - older
Breeds: Keeshond, labs, goldens, GSD
Clinical signs of hyperparathyroidism
- 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
An older, apparently healthy dog with hypercalcemia is more than likely going to have ______.
Primary hyperparathyroidism
Describe the minimum database for a dog with primary hyperparathyroidism.
CBC - usually normal, may have mild anemia
CHEM - Hypercalcemia (100% of cases); low-normal phosphorus
UA - UTI, evidence of calculi, Isosthenuria or hyposthenuria
Diagnostics for primary hyperparathyroidism
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)
Treatment for severe hypercalcemia with hyperparathyroidism
Fluid therapy: physiologic saline diuresis
Enhance renal calcium excretion
- furosemide
- glucocorticoids
- calcitonin
Inhibit bone resorption
- bisphosphonates
- glucocorticoids
- calcitonin
Suppress PTH release
- Cinacalcet
Treatment for mild/not clinical hypercalcemia with hyperparathyroidism
Monitor values
Treatment options for hypercalcemia associated with hyperparathyroidism
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
Differentials for Hypocalcemia
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
Signalment for Hypoparathyroidism
More dogs
More females
~ 5 yrs old
Poodles, Mini Schnauzers, GSD, Labrador Retrievers, Terriers
What is hypoparathyroidism?
Cessation of parathyroid function - decreased secretion of PTH
Decrease in serum calcium and increase in phosphorus
Causes of hypoparathyroidism
- Suppressed secretion of PTH without destruction (trauma, surgery)
- Atrophy - sudden correction of chronic hypercalcemia
- Iatrogenic - removal of parathyroid glands during thyroidectomy
- Idiopathic, “Primary” - immune mediated destruction
Clinical signs of hypoparathyroidism
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
Seen on physical exam with hypoparathyroidism
Changes mostly related to hypocalcemia:
- muscle fasciculations
- seizures during exam
- cardiac abnormalities may be seen (tachyarrhythmias, muffled heart sounds, weak pulses)
Diagnostics for hypoparathyroidism
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)
Treatment for hypoparathyroidism
Treatment will be lifelong
Emergency Therapy
- IV calcium gluconate given slowly IV
Chronic
- calcitriol (usually lifelong)
- calcium carbonate (can taper)
Monitoring of hypoparathyroidism
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
