endocrinology (insulinoma)

Question 1

give a definition of insulinomas and their frequency in cats

Answer 1

insulinomas are functional pancreatic tumors of the beta-cells

they are rare in cats

this is a disease of older cats (> 12 years old)

Question 2

what are the typical clinical signs seen with insulinoma

Answer 2

typical clinical signs are referable to hypoglycemia:
- weakness, staggering gait, ataxia
- lethargy
- mental dullness
- seizures (hypoglycemic seizures are common)

clinical signs tend to be episodic and have a waxing and waning course probably mainly due to the variable activity of counter-regulatory hormones

Question 3

how is the diagnosis of insulinoma made

Answer 3

demonstration of concomitant hypoglycemia and insulin levels that are elevated or in the high normal range (i.e., inappropriate insulin:glucose ratio)

Question 4

what are the main differentials for hypoglycemia

Answer 4

hepatic disease

severe sepsis

hypoadrenocorticism

non-pancreatic tumors

BUT these are generally associated with low insulin concentrations

Question 5

what are the treatment options for insulinomas

Answer 5

a hypoglycemic crisis can be managed with IV glucose (1-5 ml of 25% or 50% glucose solution followed by 5-10% dextrose solutions IV)

when an insulinoma is diagnosed, exploratory surgery may be indicated in an attempt to identify and remove the tumor

medical management if surgery is not wanted or metastatic disease is already present:
- feeding frequent meals
- prednisolone 1 mg/kg BID will likely need to be used to help control the hypoglycemia
- diazoxide (which directly inhibits insulin secretion) has been recommended in combination with prednisolone if prednisolone alone fails (start at 5 mg/kg PO BID, increasing to 30 mg/kg BID if necessary)

Question 6

what is the prognosis for insulinoma

Answer 6

the prognosis is guarded to poor

if significant hypoglycemia has occured priori to diagnosis and therapy, there may be irreversible neurological damage