5. Pituitary gland

Question 1

synthesizes ACTH

Answer 1

pars intermedia (adenohypophysis)

Question 2

antidiuretic hormone (ADH, vasopressin) and oxytocin

synthesized in the hypothalamus but are released into the bloodstream in the pars nervosa

Answer 2

neurohypophyseal hormones

Question 3

hyperadrenocorticism caused by an ACTH- secreting tumor of the pituitary gland

Answer 3

Pituitary-dependent hyperadrenocorticism (Cushing disease)

Question 4

a highly sensitive test to differentiate healthy dogs from those with hyperadrenocorticism, but it is not highly specific

Answer 4

urine cortisol to creatinine ratio (UCCR)

Question 5

screening test of choice for canine hyperadrenocorticism

tests the integrity of negative feedback

Answer 5

low-dose dexamenthasone suppresion test

Question 6

cheaper dexamenthasone; distinguishes between PDH & ADH

Answer 6

low-dose dexamenthasone suppresion test

Question 7

Disadvantages:
• 3 blood draws for dogs and 5 for cats
• More false positives due to stress
• 40-50% of dogs with non-adrenal disease had inadequate suppression at 4 and 6 hours
• No baseline for therapeutic monitoring
• Not a good test for identifying iatrogenic HAC
• cannot detect hypoadrenocorticism
• Phenobarbital will cause false positive

Answer 7

low-dose dexamenthasone suppresion test

Question 8

works on the principle that autonomous ACTH hypersecretion by the pituitary can be suppressed by supraphysiologic concentrations of steroid

Answer 8

High-dose dexamethasone suppression test

Question 9

Dogs with autonomous cortisol-producing adrenal tumors have maximally suppressed ACTH production via the normal feedback mechanism

therefore, administration of dexamethasone, no matter how high the dose, cannot suppress serum cortisol concentrations

Answer 9

High-dose dexamethasone suppression test

Question 10

able to suppress ACTH & cortisol secretion in dogs with PDH

Answer 10

High-dose dexamethasone suppression test

Question 11

Dogs with ____ do not suppress ACTH on the HDDS test

Answer 11

Pituitary macroadenomas

Question 12

can characterize multple adrenal nodules

Answer 12

High-dose dexamethasone suppression test

Question 13

much easier sample handling than Endogenous ACTH

Answer 13

High-dose dexamethasone suppression test

Question 14

Disadvantages:
• Doesn’t always distinguish between ADH and severe PDH
• Takes all day – have to plan ahead
• Have to take 5 samples from a cat

Answer 14

High-dose dexamethasone suppression test

Question 15

used to diagnose various adrenopathic disorders
1. endogenous or iatrogenic hyperadrenocorticism
2. spontaneous hyperadrenocorticism

a screening test for the diagnosis of naturally occurring hyperadrenocorticism

Answer 15

ACTH stimulation test

Question 16

has a higher specificity than LDDS test

Answer 16

ACTH stimulation test

Question 17

less affected by glucocortcoid therapy than LDD

fewer false positives due to stress than LDD

Answer 17

ACTH stimulation test

Question 18

cannot distinguish bet. PDH & ADH

Answer 18

ACTH stimulation test

Question 19

a good screening test

Positive (increased) result tells you the dog is sick

Answer 19

UCCR

Question 20

a lack of secretion of pituitary trophic hormones and diminished target organ function (eg, adrenal cortex)

dysfunction of the CNS

affected animals are often
- depressed
- incoordinated
- weak
- may collapse with exercise

Answer 20

Nonfunctional Pituitary Tumors

Question 21

invariably associated with pituitary pars intermedia dysfunction (PPID)

excessive hair growth

Answer 21

acquired hypertrichosis

Question 22

Nonfunctional tumors of the pituitary gland may lead to this as the growth of a neoplastic (but nonsecretory) cell type displaces other pituitary cells

rare disorders in dogs and cats

Answer 22

adult-onset panhypopituitarism

Question 23

Clinical signs are usually associated with
- local tissue compression
- edema associated with large tumors that act as space-occupying lesions

Answer 23

Adult-onset Panhypopituitarism

Question 24

Panhypopituitarism in young dogs that usually results from failure of the pars distalis of the pituitary to develop during gestation

This leads to a deficiency of all the pituitary trophic hormones

Answer 24

Juvenile-onset Panhypopituitarism (Dogs)

Question 25

Dwarfism results from a lack of growth hormone, with pars distalis failure causing a range of other signs related to the lack of other hormones

Answer 25

Juvenile-onset Panhypopituitarism (Dogs)

Question 26

some cases of Juvenile-onset Panhypopituitarism are caused by ____, which lead to subnormal levels of growth hormone

Answer 26

benign craniopharyngiomas

Question 27

caused by a lack of antidiuretic hormone (ADH) or an inability of the kidneys to respond to ADH

Answer 27

diabetes insipidus

Question 28

results in production of large volumes of dilute urine, which prompts animals affected by it to drink large amounts of water to compensate

Answer 28

diabetes insipidus

Question 29

done if the animal is not dehydrated and does not have renal disease

determine urine and plasma osmolality, or urine specific gravity

Answer 29

Water Deprivation test

Question 30

to differentiate among conditions that may result in large volumes of urine that is chronically low in specific gravity but otherwise normal including :
1. nephrogenic diabetes insipidus
2. psychogenic diabetes insipidus
3. hypercortisolism

used to evaluate animals in which a water deprivation test could not be performed

Answer 30

ADH response test

Question 31

caused by excess secretion of growth hormone (GH) in adult animals

in cats, it is due to GH-secreting tumors of the anterior pituitary

Answer 31

feline acromegaly

Question 32

growth of the extremities, skull, and muscles occur in some cats

Answer 32

feline acromegaly