Lecture 15 4/4/25 Flashcards
What are the mechanisms of hypoglycemia?
-decreased glucose production
-excessive use of glucose
-excess insulin or insulin-like substances
What are the characteristics of insulinoma?
-functional insulin-secreting tumor of pancreatic beta cells
-inappropriate insulin secretion in the face of hypoglycemia
-might appear clinically “normal” with mild to moderate hypoglycemia
What can cause false hypoglycemia on bloodwork?
-delayed sample handling (most common)
-improper measuring technique/equipment
-profound leukocytosis or polycythemia
What are the characteristics of stress hyperglycemia?
-transient increase in blood glucose that occurs in response to stress or illness
-usually mild, but can be pronounced (esp. in cats)
-no clinical signs
What is diabetes mellitus?
-disease of insulin deficiency
-characterized by hyperglycemia resulting from inadequate insulin secretion, action, or both
What is type 1 diabetes mellitus?
-insulin-deficient
-beta cell related disorders
What is type 2 diabetes mellitus?
-insulin-resistant
-target organ disorders
What are the characteristics of type 1 diabetes mellitus?
-absolute insulin deficiency with no endogenous insulin production
-multifactorial etiology that is poorly understood
What are the potential pathologies of type 1 diabetes mellitus?
-complete absence of pancreatic beta cells
-reduced number/size of pancreatic islets
-decreased number of beta cells
-beta cell vacuolation and degeneration
What are the characteristics of an immune-mediated etiology of diabetes mellitus?
-uncommon in dogs
-production of autoantibodies
-dog-leukocyte antigen genes encode MHC that can increase risk or be protective
Which breeds are predisposed to diabetes mellitus?
-samoyed
-westie
-mini poodle
Which exocrine pancreatic diseases can cause a loss of beta cells?
-pancreatitis
-neoplasia
-idiopathic
What are the characteristics of the relationship between pancreatitis and diabetes mellitus?
-pancreatitis is estimated to be present in 30 to 40% of dogs with DM
-“bystander” damage to islets can result in DM
-hyperglycemia and hyperlipidemia can cause pancreatitis
What can cause congenital DM?
-beta cell aplasia/abiotrophy/hypoplasia
-defects in beta cell function
-defects in insulin action
What can cause insulin-resistant DM?
-growth hormone
-steroids
-progesterone/progestins
What are the classifications of DM?
-beta cell related disorders
-congenital
-insulin-resistant
What are the key points regarding type 1 DM?
-loss of beta cells
-requires exogenous insulin
-generally irreversible; requires life long treatment
What can contribute to decreased tissue responsiveness to insulin/insulin resistance?
-obesity
-physical inactivity
-sources of inflammation
-diabetogenic drugs
-patient genetics
What is the cycle of beta cell failure?
-insulin resistance leads to impaired beta cell function and beta cell failure
-beta cell failure results in inadequate insulin secretion and decreased glucose tolerance
-decreased glucose tolerance leads to DM and gluco(lipo)toxicity
-gluco(lipo)toxicity leads to further beta cell failure
Why is type 2 DM considered potentially reversible?
-removing cause of insulin resistance can improve tissue sensitivity
-can have less hyperglycemia and reduced glucotoxicity
-can enter remission and no longer have a need for exogenous insulin
What are the characteristics of DM secondary to hypersomatotropism in cats?
-up to 25% of diabetic cats
-must be on insulin for 6 weeks prior to testing
-diagnosed via increased serum IGF-1
-treatment of excessive growth hormone allows for higher DM remission rates
What are the characteristics of DM secondary to Cushing’s in cats?
-Cushing’s is rare in cats
-nearly 80% of cats with Cushing’s also have DM
-treatment of Cushing’s does not typically reverse DM
What are the characteristics of DM secondary to Cushing’s in dogs?
-only occurs in about 8% of Cushing’s dogs
-unknown why some develop DM and others do not
-uncontrolled Cushing’s makes DM more difficult to control
What are the characteristics of gestational diabetes?
-occurs during diestrus or gestation
-progesterone stimulates growth hormone secretion; both can cause insulin resistance
-potentially reversible; must spay immediately and start animal on insulin
What is the summary for type 1 DM?
-no endogenous insulin production
-absolute insulin deficiency
-no insulin resistance
-absolute insulin dependency
-no chance for remission
-mostly seen in dogs
What is the summary for type 2 DM?
-possible to have some endogenous insulin production
-relative insulin deficiency
-insulin resistance is common
-possible insulin dependency
-chance for remission
-mostly seen in cats
What are the signs of insulin deficiency?
-hyperglycemia
-glucosuria
-polyphagia
-PUPD
What are the characteristics of glucose in the kidney?
-glucose is freely filtered and 100% reabsorbed in proximal tubule
-primarily via SGLT-2
What is the renal glucose threshold in dogs and cats?
dogs: 180 to 200 mg/dL
cats: 250 to 300 mg/dL
Why does mild hyperglycemia not lead to DM?
-often associated with stress
-levels less. tahn renal threshold allows for all filtered glucose to be absorbed
-no clinical signs occur
What happens when the hyperglycemia is above the renal threshold?
-glucosuria
-osmotic diuresis
-PUPD
What are the consequences of insulin deficiency?
-poor wound healing
-catabolism and weight loss
-amino acids being directed into gluconeogenesis
What are the hallmark clinical signs of DM?
-typically acute onset
-systemic illness/diabetic ketoacidosis
What are potential complications of DM?
-infections
-delayed wound healing
-diabetic cataracts
What are the characteristics of diabetic cataracts?
-common in dogs; 80% of patients develop them within 1 year
-rare in cats
-not related to glycemic control
-changes in lens osmolarity lead to influxes of water, rupture of lens fibers, and lens-induced uveitis
What are the possible PE findings in DM patients?
-obesity
-weight loss if dz untreated for long time
-possible hepatomegaly
-possible dull, dry, brittle hair coat
-possible secondary infections
What is the diagnostic criteria for diagnosing DM in dogs?
-blood glucose >/= 200 mg/dL AND clinical signs
OR
-hyperglycemic crisis/DKA
What is the diagnostic criteria for diagnosing DM in cats?
-blood glucose >/= 270 mg/dL AND clinical signs
AND
-either increased glycated proteins or glucosuria
OR
-hyperglycemic crisis/DKA
What are the characteristics of fructosamine?
-glycosylated albumin that reflects average BG over the life-time of albumin
-higher values in cases of poor glycemic control
-not affected by stress
-less reliable for monitoring of treatment
What are the characteristics of Hb A1C?
-glycosylated hemoglobin that assesses glycemic control over lifespan of RBC
-gold standard in humans
-not widely used in vet med
What is clinical DM diagnosis based on?
-clinical signs
-persistent hyperglycemia
-persistent glucosuria
What is the minimum diagnostic info needed to diagnose diabetes mellitus?
-blood glucose
-urine dipstick
What other diagnostics are ideal when diagnosing DM?
-CBC
-chem/lytes
-UA
-blood pressure
-fructosamine
-urine culture
-total T4 (cats)
