Endocrinology - Glucose homeostasis... Flashcards

1
Q

Glucose is the sole source of energy for the ________.

A

brain

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2
Q

What is the range for normal blood glucose?

A

70-120 mg/dl

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3
Q

What are the exogenous sources of glucose?

A

intestinal absorption

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4
Q

What are the endogenous sources of glucose?

A

glycogenolysis and gluconeogenesis

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5
Q

Post-prandially, how long does glucose provide fuel for and for what?

A

fuel for 4-8 hours of cell metabolism

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6
Q

In the fasted state, what sources maintain normoglycemia?

A

The endogenous sources

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7
Q

What is glycogenolysis?

A

breakdown of hepatic glycogen stores into glucose

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8
Q

When are the hepatic glycogen stores exhausted during fasting?

A

after 2-3 days of fasting

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9
Q

When glycogen stores are depleted in fasted patients, what takes over to maintain normoglycemia?

A

gluconeogenesis

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10
Q

What is gluconeogenesis?

A

The formation of glucose from precursors

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11
Q

What are the precurosors for gluconeogenesis?

A

Amino acids, glycerol, and lactate

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12
Q

Where does gluconeogenesis occur?

A

Mainly in the liver, but it can also occur in the kidney

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13
Q

Aside from the exogenous and endogenous sources of glucose, what is also required for normoglycemia?

A

hepatic function/hepatic blood supply and a functioning endocrine system

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14
Q

What does insulin do?

A

Promote the cellular uptake of glucose, AA, FA, and electrolytes
Promotes the storage of glucose as glycogen
Inhibits lipolysis and subsequent release of FFA into circulation
Inhibits gluconeogenesis and glycogenolysis

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15
Q

Hypoglycemia is when BG falls below what level?

A

70 mg/dl

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16
Q

What is the normal response to hypoglycemia?

A

There is a stimulation of a release of diabetogenic hormones - glucagon, cortisol, catecholamines, and growth hormone (unimportantly progesterone and thyroxine too)

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17
Q

What is the net effect of the diabetogenic hormones?

A

Promote gluconeogenesis and glycogenolysis, decrease peripheral glucose use, and shut down insulin secretion

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18
Q

What is the net result of the effect of diabetogenic hormones?

A

to normalize blood glucose levels

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19
Q

What hormones increase BG?

A

cortisol, epinehrine, glucagon, and growth hormone

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20
Q

What hormone decreases BG?

A

insulin

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21
Q

What can cause hypoglycemia?

A

Lack of intestinal absorption, lack of hepatic production, endocrine disorders, increased glucose utilization, and miscellaneous

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22
Q

What can cause lack of intestinal absorption of glucose?

A

severe malnutrition/starvation and severe intestinal disease

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23
Q

What can cause lack of hepatic production of glucose?

A

Portosystemic shunts, hepatic failure, and glycogen storage diseases

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24
Q

What are the sub-categories of endocrine disorders can cause hypoglycemia?

A

Lack of diabetogenic hormones or too much insulin

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25
Q

What endocrine disorders can cause lack of diabetogenic hormones?

A

hypoadrenocorticism - cortisol deficiency

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26
Q

What endocrine disorders can cause the production of too much insulin?

A

iatrogenic and insulinoma

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27
Q

What can cause increased glucose utilization?

A

sepsis, pollycythemia, and extreme exertion

28
Q

What miscellaneous causes can lead to hypoglycemia?

A

Juvenile hypoglycemia, xylitol toxicity, paraneoplastic, and artifact

29
Q

What is the pneumonic to remember the eitiologies for hypoglycemia?

A

SHIN SPLATS - Sepsis, Hunting dog hypoglycemia, Insulin overdose/iatrogenic, Neoplasia, Spurious, Puppy or polycythemia, Liver disease, Addison’s disease, Toxin, and Storage diseases

30
Q

What is the first area affected by hypoglycemia?

A

the cerebral cortex

31
Q

Clinical signs from hypoglycemia in the brain result from what?

A

Neuroglycopenia and sympathoadrenal stimulation

32
Q

What is neuroglycopenia?

A

lack of glucose to the brain

33
Q

What is sympathoadrenal stimulation?

A

The release of epinephrine as a result of hypoglycemia

34
Q

What are the clinical signs of neuroglycopenia?

A

weakness, lethargy, behavioral change, ataxia, seizures, and coma

35
Q

What are the clinical signs associated with sympathoadrenal stimulation?

A

Think of someone that is hangry - muscle tremors, nervousness, restlessness, and hunger

36
Q

What is an insulinoma?

A

A tumor of pancreatic beta cells that autonomously secretes insulin

37
Q

Insulinomas are common in _____, uncommon in ______, and rare in _______.

A

ferrets, dogs, and cats

38
Q

What breed of dog is over-represented in insulinomas? Age of diagnosis?

A

Large breeds are over-represented and average age is 9-10 years

39
Q

Are the majority of insulinomas benign or malignant?

A

malignant

40
Q

What is the behaviorof insulinomas?

A

Chronic, insidious onset - at the time of diagnosis a majority of them metastasize

41
Q

How may patients with insulinomas present?

A

They may have severe hypoglycemia with relatively mild clinical signs

42
Q

How are insulinomas diagnosed?

A

By demonstrating high insulin with concurrent low glucose - you must measure insulin when BG is low (i.e. prior to stabilization of the patient)

43
Q

If BG is <50 mg/dl and insulin is above the reference range, what is the likelihood that the cause is due to an insulinoma?

A

a high probability

44
Q

If BG is <50 mg/dl and insulin is low, what is the chance that an insulinoma is the cause?

A

it should be ruled out

45
Q

If the insulin:glucose ratio is greater than 30, what should you suspect?

A

hyperinsulinemia

46
Q

What is the recommended emergency therapy for hypoglycemia?

A

IV catheter, 50% dextrose solution, and Administer glucose slowly over 10 minutes

47
Q

Why do we want to treat for clinical signs associated with hypoglycemia and not the number?

A

Because if the reason for hypoglycemia is due to an insulinoma, the increase in BG will promote insulin release ultimately worsening the hypoglycemia

48
Q

What some alternative options to using glucose to treat hypoglycemia?

A

glucagon and dexmedetomidine CRI

49
Q

Why would you want to give dexmedetomidine to treat hypoglycemia?

A

it antagonizes insulin

50
Q

When is hyperglycemia a normal finding?

A

2-4 hours post prandial - it is mild

51
Q

What are the etiologies of hyperglycemia?

A

Too much of one (or more) hormones that raise BG, deficiency in hormone that decreases BG, and miscellaneous

52
Q

What hormones can cause hyperglycemia if they are in excess?

A

cortisol, growth hormone, epinephrine, glucagon, and progesterone

53
Q

True or False: If there is excess of a hormone, hyperglycemia is not usually the sole clinical presentation.

A

TRUE

54
Q

When is therapy for hyperglycemia indicated?

A

Usually only if diabetes develops as a complication of the primary endocrine disease

55
Q

What are the sources of stress hyperglycemia?

A

Catecholamine release and glucocorticoids

56
Q

What is the renal threshold for glucose in dogs?

A

180 mg/dl

57
Q

What is the renal threshold for glucose in cats?

A

280 mg/dl

58
Q

What disease process that is due to low insulin can cause hyperglycemia?

A

Diabetes mellitus

59
Q

What is the pathophysiology of insulin deficiency in diabetes mellitus?

A

There is decreased tissue utilization of glucose, increaed hepatic glycogenolysis and gluconeogenesis, and then the glucose from the liver accumulates in the circulation resulting in hyperglycemia

60
Q

How does hyperglycemia in diabetes mellitus patients lead to glucosuria?

A

The high glucose levels exceeds renal tubular reabsorptive abilities

61
Q

How does hyperglycemia in diabetes mellitus patients lead to polyuria?

A

It causes osmotic diuresis

62
Q

Why does polydipsia follow polyuria in diabetes mellitus patients?

A

it is a compensatory mechanism to prevent dehydration

63
Q

Why does polyphagia occur in the face of hyperglycemia in diabetes mellitus patients?

A

Normally, the satiety center inhibits the feeding center after a meal. In order to do this, the satiety center requires insulin for glucose transport. When insulin is defficent, glucose does not enter the satiety center and therefore fails to inhibit the feeding center. Polyphagia is the result

64
Q

What are the clinical signs of diabetes mellitus?

A

polyuria, polydipsia, polyphagia, and weight loss

65
Q

How is diabetes mellitus diagnosed?

A

Resting hyperglycemia with glucosuria in an animal with compatible clinical signs