Pituitary Gland Pathology

Question 1

what are the three possible outcomes of endocrine pathology

Answer 1

1. increased function
2. decreased function
3. no change in function

Question 2

what is the progression of endocrine disorders of growth

Answer 2

hyperplasia –> adenoma –> carcinoma

Question 3

hyperplasia

Answer 3

non-neoplastic proliferation; still has some regulatory capacity

Question 4

diffuse hyperplasia

Answer 4

growth of the entire organ (hyperplasia and hypertrophy)

Question 5

nodular hyperplasia

Answer 5

“adenomatous”
multiple well-demarcated nodules that are NOT encapsulated

difficult to differentiate from adenomas

Question 6

adenoma

Answer 6

benign neoplasia
solitary, thinly encapsulated, well-demarcated masses

often compresses surrounding tissues

Question 7

carcinoma

Answer 7

large, invasive, metastatic, malignant neoplasia

rare

Question 8

what is the main difference in pituitary anatomy of cows

Answer 8

has a layer of dura mater over top of the pituitary gland

prevents dorsal deviation of the pituitary into the brain

Question 9

histology of pars distalis

Answer 9

dark pink staining region

acidophils: dark pink cells
basophils: blue cells
chromophobes: non-staining cells

Question 10

what is the function of the pars distalis

Answer 10

secretes the majority of trophic pituitary hormones

LH, FSH, GH, TSH, ACTH/MSH, prolactin

Question 11

histology of pars nervosa

Answer 11

light pink staining region (glia)

Question 12

function of the pars nervosa

Answer 12

secretes ADH, oxytocin

Question 13

histology of pars intermedia

Answer 13

blue/basophilic staining region
junction between pars distalis and nervosa

contains Rathke’s pouch (not in horses)

Question 14

function of pars intermedia

Answer 14

secretes ACTH/MSH in dogs and horses

Question 15

four main categories of pituitary pathology

Answer 15

1. juvenile panhypopituitarism
2. failure of fetal endocrine function
3. diabetes insipidus
4. acquired diseases

Question 16

juvenile panhypopituitarism

Answer 16

congenital failure of the pars intermedia and distalis to develop

Question 17

what is the main lesion associated with juvenile panhypopituitarism

Answer 17

proportionate dwarfism

low GH, FSH, LH, TSH

Question 18

does ACTH increase/decrease/no change with juvenile panhypopituitarism

Answer 18

no change (normal)

Question 19

what are associated lesions with juvenile panhypopituitarism

Answer 19

• truncal alopecia (non-inflammatory/pruritic)
• delayed permanent teeth
• cystic rathke’s pouch

Question 20

what species is juvenile panhypopituitarism most common in

Answer 20

dogs

Question 21

failure of fetal endocrine function

Answer 21

congenital failure of fetal pituitary function

Question 22

what is the main outcome associated with failure of fetal endocrine function

Answer 22

delayed parturition

loss of dam ACTH –> lack of signaling to uterus –> failure to produce PGF2a –> failure to signal parturition –> prolonged gestation

Question 23

what species is failure of fetal endocrine function most common in

Answer 23

ruminants

Question 24

what are common causes of failure of fetal endocrine function

Answer 24

congenital:
1. genetic
2. infectious
3. toxic

Question 25

infectious causes of failure of fetal endocrine function

Answer 25

BVDV - leads to hydranencephaly (cortex lobes replaced by CSF), which causes pituitary and hypothalamic dysfunction

Question 26

toxic causes of failure of fetal endocrine function

Answer 26

sheep: skunk cabbage ingestion by the dam at a certain period in gestation
- interferes with fetal signaling
- malformation of the fetal brain and pituitary
- failed endocrine function

concurrent lesion: cyclopia

Question 27

diabetes insipidus

Answer 27

vasopressin (ADH) deficiency OR resistance

Question 28

what is the main outcome of diabetes insipidus

Answer 28

increased production of hypotonic urine (USG <1.005)

Question 29

what are the two causes of diabetes insipidus

Answer 29

1. neurogenic: leads to decreased production of ADH
2. nephrogenic: leads to decreased response to ADH

Question 30

what are examples of acquired pituitary diseases

Answer 30

1. hypophysitis
2. disorders of growth
3. equine pituitary pars intermedia dysfunction

Question 31

hypophysitis

Answer 31

inflammation of the pituitary gland

suppurative infiltrate (neutrophils) in pars distalis/intermedia

Question 32

disorders of growth

Answer 32

hyperplasia or neoplasia (adenoma)

Question 33

what species are disorders of growth most common in

Answer 33

dogs, cats, horses, pigs

Question 34

what are the possible outcomes of disorders of growth

Answer 34

1. hyperpituitarism
2. hypopituitarism
3. no change

Question 35

what is the most common outcome and clinical signs of ACTH secreting pituitary gland adenomas

Answer 35

hyperadrenocorticism

increased ACTH –> increased cortisol production from adrenal

clinical signs: PU/PD/PP, panting, redistribution of fat (pot belly), truncal alopecia

Question 36

what is the most common outcome of GH secreting pituitary gland adenomas

Answer 36

diabetes mellitus

Question 37

equine pituitary pars intermedia dysfunction (EPPID)

Answer 37

most common endocrinopathy of horses

hyperplasia or adenoma of the pars intermedia

Question 38

pathogenesis of EPPID

Answer 38

1. injury to dopaminergic cells
2. imbalance of dopamine and serotonin
3. serotonin predominates
4. hyperplasia of melanotrophs
5. increase in POMC derivative hormones

Question 39

what are the POMC derivative hormones

Answer 39

ACTH, MSH, endorphins

Question 40

clinical signs of EPPID

Answer 40

hirsutism (failure to shed coat leading to fluffy coat)
PU/PD
laminopathy
fever
polyphagia
hyperhidrosis

Question 41

secondary lesions associated with EPPID

Answer 41

1. compression atrophy of hypothalamus
2. diffuse hyperplasia of adrenal cortex (from ACTH overproduction)