Pheochromocytoma and hyperthyroid

Question 1

Pheochromocytoma:
Incidence
Site
Malignancy

Answer 1

Rare tumor, of the adrenal medulla. In dogs, up to 50% are malignant and can show metastatic behavior.
Signs seen are d/t epi or norepi- release.

Question 2

What are the primary effects of norepinephrine?

Answer 2

alpha-adrenergic stimulator

arteriolar and venular constriction, increase systolic and diastolic BP.

Question 3

What are the primary effects of epinephrine?

Answer 3

both alpha and beta adrenergic actions.
Beta - arterial dilation, ^HR,, ^atrial contractility, ^cardiac automaticity and conduction velocity, bronchiolar smoother muscle dilation, increased lipolysis, and CNS stim.

Question 4

S/S of pheochromocytoma

Answer 4

S/S are dependent upon type and frequency of catecholamine secretion.

• anxiety
• mental depression
• restlessness
• panting
• paroxysms of blanching or flushing
• tachycardia that is sometimes accompanied by VPCs
• paroxysmal weakness or collapse
• hypertension +/- retinopathy
• weight loss, anorexia.

Question 5

Pheo Tx

Answer 5

Surgical
Medical:
-phenoxybenzamine alpha blockade PO
-regitine (phentolamine) alpha blocker parenteral
-propranolo beta blockade.
Also, alpha block before you beta block.

Question 6

Phenoxybenzamine

Answer 6

Alpha blocker.

Surgical survival in dogs that received at 1-2mg/kg per day for 2 weeks prior to surgery.

Question 7

How do you diagnose pheochromocytoma?

Answer 7

• Hx
• PE
• Imaging: xrays may see adrenal tumor. U/S, CT.
• Blood pressure measurements.
• Elevated urinary epinephrine.
• Plasma free normetanephrine concentration to have excellent sensitivity and specificity.
• Plasma free metanephrine has moderate sensitivity and high specificity.

Question 8

What structure may a pheochromocytoma invade?

Answer 8

posterior vena cava

Ascites often seen in these cases and needs to be differientiated from other possible causes; right sided CHF, chronic liver disease, hypoproteinemia, and other abdominal tumors.

Question 9

Incidence of hyperthyroidism

Answer 9

Older cats
Mean age 13 y (1-22)
Only 5% are < 10yr at time of dx.
No breed or sex predilection.

Question 10

Thyroid pathology

Answer 10

Unilateral 30%
Bilateral 70%

Adenomatous hyperplasia 98%
Adenocarcinoma 2%

Question 11

What are typical s/s associated with hyperthyroidism?

Answer 11

wt loss, despite polyphagia
v/d
PU/PD
restlessness, nervousness
unkempt hair coat
tachycardia +/- murmur
palpable goiter
\+/- hyperthyroidism
\+/- retinal hemorrhage

Question 12

What are the treatment options for hyperthyroidism?

Answer 12

Surgical
Radiation
Medical management

Question 13

Drug used to treat hyperthyroidism

Answer 13

Tapezole = methimazole

Question 14

Toxic effects of methimazole

Answer 14

anorexia
vomiting
lethargy
facial pruritus
bleeding diathesis
icterus/hepatopathy
hematologic effects (thrombocytopenia, eosinophilia, lymphocytosis, etc)

Question 15

Surgery pre-op requirements for thyroidectomy

Answer 15

restore euthyroidism
assess kidney function
propranolol or atenolol to counter tachycardia
Anesthesia: avoid atropine, ace, and ketamine.

Question 16

Post-op thyroidectomy tx

Answer 16

monitor for hypocalcemia (<7.5 mg/dl), with bilateral removal. This is true especially for the 1st 24 hrs. Can rx 10% calcium gluconate if indicated.
Thyroxine to tx HYPOthyroidism if indicated (0.2 mg/day)

Question 17

Hyperthyroidism: frequency of relapse post-op

Answer 17

intracapsular > extracapsular

Question 18

Hyperthyroid effects on chronic renal disease

Answer 18

Hyperdynamic renal blood flow
Increased GFR
Masks underlying renal pathology.
Euthyroid state precipitates decompensating renal diz.
Providing thyroxine will slow down renal deterioration after euthyroid restored.