Parathyroid Disease Flashcards
(88 cards)
1
Q
Where is 99% of calcium in the body?
A
- 99% bone/teeth
- Remaining 1% intracellular
- 0.1% extracellular
2
Q
Forms of calcium
A
- 50-60% ionized (biologically active form)
- 30-40% protein bound
- 10% chelated/complexed (phosphate, citrate, sulfate, bicarbonate)
3
Q
Where is parathyroid hormone made?
A
- parathyroid glands
4
Q
Where is calcitriol activated?
A
- Activation occurs in the kidney
5
Q
Where is calcitonin made?
A
- Thyroid gland
6
Q
What three hormones are involved in calcium regulation?
A
- Calcitriol
- Parathyroid hormone
- Calcitonin
7
Q
How many parathyroid glands are there?
A
2 pairs (4 total)
8
Q
What cells in the parathyroid gland make parathyroid hormone?
A
- Chief cells
9
Q
Actions of PTH (broad)
A
- maintain plasma ionized calcium levels
- Regulate plasma phosphorus levels
10
Q
What three organs does PTH act on?
A
- Bone
- Kidney
- Small intestines
11
Q
PTH effect on bone
A
- Increase resorption (release) of calcium and phosphorus
- Increases blood levels of both
- Ultimately increases phosphorus and increases calcium
12
Q
PTH effect on the kidney
A
- Increase calcium reabsorption (distal tubules and collecting ducts)
- Increase phosphorus excretion (proximal tubules)
- Serum calcium goes up, phosphorus goes down
- Also stimulates synthesis of the active form of Vitamin D (via increased activity of 1-alpha-hydroxylase)
- Ultimately: Increases calcium and decreases phosphorus
13
Q
PTH effect on small intestines
A
- Indirectly via increase in calcitriol, leading to an increase in calcium and phosphorus
- Ultimately: Increases calcium and increases phosphorus
14
Q
What are the there places where calcitriol works in the body?
A
- Small intestine
- Bone
- Parathyroid glands
15
Q
Calcitriol effect on the small intestine
A
- Increases formation of calcium binding protein (CBP) which transports calcium from the lumen into the intestinal epithelial cells
16
Q
Calcitriol effect on bone
A
- In large quantities stimulates bone resorption thus increasing calcium and phosphorus
17
Q
Calcitriol effect on parathyroid glands
A
- Negative feedback leads to decreased PTH
18
Q
Where is calcitonin made?
A
- Parafollicular cells (C cells) of the thyroid
19
Q
Function of calcitonin
A
- Decrease serum calcium concentration
20
Q
Calcitonin effects
A
- Works on bone
- Decreases osteocytic membrane activity
- Decreases osteoclast formation
21
Q
Significance of calcitonin compared to PTH
A
- Much less significant
22
Q
Look at the chart on Dr. Haines’s slides with the Ca/P summary - seriously do it! It’s helpful
A
do it
23
Q
What happens to PTH as calcium goes up?
A
- PTH will go down
24
Q
What happens to PTH as calcium goes down?
A
- PTH will go up
25
Calcium regulation general
- maintained in a very tight range
26
What are the three components of total calcium?
- Ionized, protein bound, and chelated forms
27
How would you confirm hypercalcemia if you have an animal with an elevated total calcium level?
- Need to get an ionized calcium
28
Differentials for hypercalcemia
HOGS IN YARD
- Hyperparathyroidism (1°)
- Osteolytic
- Granulomatous
- Spurious
- Idiopathic (cats), Iatrogenic (meds, supplements)
- Neoplasia (lymphoma, anal sac adenocarcinoma)
- Young
- Addison's
- Renal disease
- D toxicosis (vitamin D)
29
Which differentials for hypercalcemia are driven by PTH?
- Hyperparathyroidism (primar)
| - Neoplasia
30
Which differentials for hypercalcemia are not driven by PTH?
- Granulomatous disease
- Renal disease
- Vitamin D toxicosis
31
What differentials for hypercalcemia are not driven by PTH and are also calcitriol driven?
- Granulomatous disease
| - Vitamin D toxicosis
32
Hyperparathyroidism mechanism of hypercalcemia
- Increased PTH that does not respond to negative feedback of elevated calcium
33
Lab findings of hyperparathyroidism (primary)
- Increased iCa
- PTH (high or inappropriately normal)
- Increased Vit D
- Decreased phosphorus
34
Causes of granulomatous disease
- disseminated fungal disease
35
Mechanism of hypercalcemia in Granulomatous disease
- Increased Vit D levels via activated macrophages
36
Lab findings for Granulomatous disease
- Increased Ca
| - Normal or increased phosphorus
37
Which neoplasias can lead to hypercalcemia?
- Lymphosarcoma (esp T cell)
- Multiple myeloma
- Adenocarcinoma of anal sac and mammary glands, etc.
38
What is the mechanism of hypercalcemia in neoplasia?
- PTH-rp (related peptide)
39
Lab findings for Neoplasia hypercalcemia
- Increased iCa (and usually total)
- Regular PTH will be inappropriately normal or decreased
- Phosphorus decreased to normal
40
What is the mechanism of hypercalcemia in renal disease?
1. Decreased excretion of Phos, Ca, and PTH by poorly functional kidneys OR
2. Renal secondary hyperparathyroidism
41
Lab findings for renal disease (relevant to hypercalcemia)
- Possibly high total Ca, usually normal iCa, PTH normal, Phosphorus high
42
What is the mechanism of hypercalcemia in Vitamin D toxicosis?
- Increased Ca and Phos bone release and intestinal absorption
43
What can cause vitamin D toxicosis?
- Cholecalciferol rodenticide, dietary supplements, Psoriasis cream, some plants
44
Lab findings for Vitamin D toxicosis
- High calcium and phosphorus
45
Primary hyperparathyroidism definition
- Excessive production of PTH by the parathyroid glands
46
Primary hyperparathyroidism Causes (3, and which is most likely?)
- Parathyroid Adenoma (most common)
- Parathyroid Carcinoma
- Parathyroid Hyperplasia
- Can affect 1+ gland
47
Typical age of Primary hyperparathyroidism
- Middle aged to older
48
Typical sex of PHP
- No sex predilection
49
Typical Breeds of PHP
- Keeshonds
| - Labs, Goldens, German Shepherds
50
Will most dogs with PHP be clinical or not?
- Most dogs with PHP are usually NOT CLINICAL
51
Clinical signs of PHP if present
- PU/PD
- Lethargy/Weakness
- Urinary signs: infections, calculi
- Long standing hypercalcemia can lead to renal failure
52
Typical physical exam findings for a dog with PHP
- Most of the time normal
| - Any signs present are often subtle or non-specific, related to urinary issues, or due to unrelated causes
53
What cause of hypercalcemia would you expect in an older, apparently healthy dog with hypercalcemia?
- More than likely going to have PHP
54
What tends to be a unifying feature of dogs with hypercalcemia not due to PHP? (IMPORTANT)
- Many other causes generally result in a sick to very sick dog
55
CBC findings in PHP
- Usually normal
| - Small % may have mild anemia
56
Chem panel findings in PHP
- Hypercalcemia (All)
| - Low or low normal phosphorus (most)
57
UA findings in PHP
- Isosthenuria or hyposthenuria
- UTI
- Evidence of calculi
58
Typical Malignancy Panel with Primary HyperPTH
- iCa
- PTH
- PTHrp (PTH related peptide)
- iCa: high
- PTH: normal
- PTHrp: normal (AKA low)
- Elevated iCa and inappropriately normal PTH is consistent with HyperPTH
- Lack of PTHrp does not completely rule out neoplasia
59
PHP further diagnostics
- Abdominal radiographs, ultrasound, or CT
- Thoracic radiographs or CT
- Cervical ultrasound or CT
60
Abdominal radiographs, ultrasound, or CT of an animal with PHP findings (possibly)
- Nephroliths, cystic calculi
| - stones are fairly common
61
Thoracic radiographs or CT of an animal with PHP
- Look for evidence of metastasis
62
Cervical ultrasound or CT of an animal with PHP
- A mass in the area of the thyroid glands supports PHP
| - Parathyroids should be <3 mm but can be difficult to visualize
63
Treatment for PHP if severely hypercalcemic (e.g. iCa >2)
- Fluid therapy
- Diuretics
- Glucocorticoids
- Bisphosphonates
- Calcitonin
- Can do surgery of affected glands (would likely want to stabilize first)
- Radiofrequency heat ablation
- Ethanol ablation
64
Treatment for PHP if mild and not clinical
- Monitor
+/- Can do surgery of affected glands (would likely want to stabilize first)
+/- Radiofrequency heat ablation
+/- Ethanol ablation
65
Surgical management of PHP
- Normal parathyroid glands may be atrophied due to constant negative feedback from overactive parathyroid gland PTH production
- After surgery, hypocalcemia can occur until the glands recover
66
What should you start before and after surgery to remove a PTH producing tumor
- Start prophylactic calcitriol (vitamin D) therapy
- Start 1-2 days prior to surgery
- Slowly taper over 2-4 months by gradually increasing the time between doses
- Short term Ca2+ supplementation (Ca carbonate AKA tums) and taper slowly over 2-4 months
- Goal is to keep Ca2+ high enough tp prevent clinical signs (normal set point is also higher, so they can start showing clinical signs at a higher than normal set point)
67
What would you worry about if you did not treat primary hyperparathyroidism?
- If hypercalcemia is present long enough it can lead to renal failure
68
Hypoparathyroidism definition
- Cessation of parathyroid function
69
Classic lab characteristics of hypoparathyroidism
- Decrease in serum calcium and an increase in phosphorus
70
Decreased secretion of PTH effect on bone
- Reduced bone resorption of calcium and phosphorus
71
Decreased secretion of PTH effect on kidneys
- Decreased calcium, magnesium, and hydrogen ion reabsorption
- Increased phosphorus, sodium, potassium, and amino acid reabsorption by the kidneys
72
What are 4 potentials causes of HypoPTH?
1. Suppressed secretion of PTH without destruction (e.g. trauma from surgery or other)
2. Atrophy - sudden correction of chronic hypercalcemia (post-op parathyroidectomy for PHP)
3. Iatrogenic - removal of parathyroid glands during removal of thyroid glands
4. Idiopathic - destruction of parathyroid gland (Primary; suspected immune mediated destruction)
73
Differentials for hypocalcemia
- P = phosphate enemas
- E = eclampsia
- A = albumin decrease
- C = chronic renal disease
- E = ethylene glycol toxicity/acute kidney injury
- P = PTH deficiency
- A = Acute pancreatitis
- I = intestinal malabsorption
- N = nutritional (vit D deficiency)
and many more!!!
74
HypoPTH more common in cats or dogs?
- Dogs
75
Average age of HypoPTH
4.8 years
76
Sex predisposition in HypoPTH
- Females more common than males
77
HypoPTH Breeds
- Poodles
- Mini Schnauzers
- German Shepherds
- Labrador Retrievers
- Terriers
78
Timing of clinical disease in HypoPTH
- Signs often present suddenly
| - True course of disease is gradual in onset
79
Two most common clinical signs of HypoPTH
- Seizures prior to diagnosis (Common
- 80%)
- Intense facial rubbing/biting or licking paws (Common - 60%)
80
Other clinical signs of HypoPTH
- Tetany/muscles spasms
- Tense/nervous
- Stiff/stilted gait
- Anorexia
- Lethargy/weakness
- Panting
- Vomiting/Diarrhea
- Cataracts
- Fever
- Growling
- Cardiac abnormalities
81
Changes on physical exam with HypoPTH
- Muscle fasiculations
- Seizures during exam
- Cardiac abnormalities in up to 40% (Tachyarrhythmias, muffled heart sounds, weak pulses)
- May not be contracting as well
82
Diagnosis of HypoPTH based on labwork
- Clinical signs = decreased serum Calcium
- Rule out other dfdx
- Increased serum Phosphorus
- Ionized calcium decreased
- PTH and calcitriol levels
83
PTH and Calcitriol levels in HypoPTH
- Parathyroid hormone low to low normal
| - Decreased calcitriol
84
Duration of treatment for HypoPTH
- LIFELONG
85
Emergency therapy for hypocalcemia (HypoPTH)
- IV calcium gluconate
- Give SLOWLY (10-30 minutes)
- If given too quickly you can stop the heart
- Subcutaneous administration an option after tetany is controlled
- Use diluted 10% Ca Gluconate only
- Potential risk of inflammation or skin sloughing
86
Treatment for HypoPTH
- Calcitriol (oral or injectable)
- Generally lifelong
- Oral calcium
- Calcium carbonate - Tums
- Can usually be tapered down or stopped after stabilization of disease
87
Monitoring of HypoPTH
- Frequent rechecks of iCa if necessary
| - Every animal responds differently to calcitriol and dose and frequency adjustments are often needed
88
Goal of HypoPTH therapy
- Low normal or slightly low calcium levels
| - Avoid hypercalcemia due to risk of renal failure and other complications
