Ex 4 - Pathology of Pit and Adrenal Glands

Question 1

Adenohypophyseal aplasia (dogs/cattle)

Answer 1

• fetus is unable to produce cortisol –> fetal stress is the signal for parturition to occur
• caused by ingested toxins, e.g. Verratrum californium
• Development/growth ceases in late term pregnancy –> gestation continues well beyond term

Question 2

Hyperadrenocorticism (Cushing’s) - Clinical signs

Answer 2

• usually a disease of older dogs
• PU/PD
• alopecia/skin disease
• polyphagia/weight gain
• pot belly
• acute dyspnea –> puimonary thromboembolism

Question 3

Hyperadrenocorticism (Cushing’s) - Clin Path

Answer 3

• Stress leukogram
• thrombocytosis
• mild hyperglycemia
• hypercholesterolemia
• marked elevation in ALP

Question 4

Hyperadrenocorticism (Cushing’s) - Gross Pathologic Findings

• Adrenal glands
• Kidneys
• Pit gland
• Vessels (arteries)
• Liver
• Dermal condition

Answer 4

• Bilateral enlargement of adrenal glands
• = diffuse adrenocortical hyperplasia
• this means the disease is in the pituitary!
• Kidney capsules may be hemorrhagic, due to thrombotic events
• = acute renal infarction
• Pituitary adenomas are common
• carcinomas are less common
• 85% of dogs with Cushing’s are pituitary-dependent
• 15% of dogs are adrenal dependent –> one gland is hypertrophic, the other is atrophied
• Arterial thrombi
• adhered to vessel wall, granular surface, dull, laminar on cross-section
• cortisol prevents production of antithrombins –> hyper coagulable state
• Hepatomegaly
• Multifocal dermal mineralization (Calcinosis cutis)

Question 5

Hypoadrenocorticism (Addison’s) - Clinical presentation

Answer 5

• Intermittent or waxing/waning signs
• Lethargy, collapse
• Commonly young adult dogs

Question 6

Hypoadrenocorticism (Addison’s) - Clin Path

Answer 6

• Mild, non-regenerative anemia
• lack of a stress leukogram***
• Hypoglycemia
• Hyperkalemia
• Hyponatremia/hypochloremia
• Azotemia + minimally concentrated urine
• Na:K ratio is < 25:1

Question 7

Hypoadrenocorticism (Addison’s) - Gross pathologic findings

Answer 7

Adrenocortical atrophy!

Question 8

Hypoadrenocorticism (Addison’s) - Pathogenesis

Answer 8

• Suspected immune-mediated process
• adrenocortical atrophy
• -> loss of aldosterone & cortisol
• -> Na loss and K retention
• Often insidious onset with non-specific clinical signs
• -> acute circulatory collapse may be most obvious sign
• -> CV manifestations due to hyperkalemia and increased water loss
• Glucocorticoid synthesis decreased/lost
• -> Hypoglycemia
• Azotemia due to loss of normal osmotic gradient –> dehydration
• Non-regenerative anemia
• -> cortisol promotes erythropoiesis (no cortisol, no RBC production)

Question 9

What is the key feature of hypoadrenocorticism

Answer 9

Lack of stress leukogram

Question 10

Equine PPID - Causes (MD’s)

Answer 10

1. Diffuse hypertrichosis
2. Pituitary adenoma of the pars intermedia
   - poorly formed sella turcica bone in the horse –> compression of pit gland
3. Laminitis

Question 11

Equine PPID - Pathogenesis

Answer 11

1. Idiopathic, age-related loss of dopamine inhibition
2. Increase secretion of POMC derivatives (MSH, and ACTH to a lesser extent)
3. Cortisol is a counter-regulatory hormone of insulin
   - increased cortisol results in insulin resistance –> hyperglycemia

Question 12

Feline acromegaly

Answer 12

• Acquired syndrome - occurs in older cats (usually tumor related)
• Results in widening and/or elongation of bones by appositional growth (physes are closed)
• Severe hyperglycemia
• growth hormone interfere with insulin pathways
• become severely diabetic and ill

Question 13

Feline acromegaly - Clin Path

Answer 13

1. Hyperglycemia
2. Stress leuk + mild erythrocytosis
3. Elevated liver enzymes
4. Hyperphosphatemia w/out renal azotemia, mild proteinuria
5. Marked glucosuria

Question 14

Feline acromegaly - PE findings

Answer 14

• Oval shaped eyes
• Broadening of the maxilla
• large paws

Question 15

Feline acromegaly - MD

Answer 15

• Pituitary acidophil adenoma –> very treatable with tumor irriadiation
• Diffuse islet cell degeneration with amyloidosis –> hyperglycemia
• Proliferative and sclerosing glomerulonephropathy –> proteinuria

Question 16

Feline acromegaly - Pathogenesis

Answer 16

• Acquired excess of GH due to adenoma of the pituitary
• Uncontrolled diabetes is typical presentation
• GH mediated insulin resistance
• Beta cell exhaustion

Question 17

Adrenal associated endocrinopathy - Ferrets

Clinical presentation

Answer 17

• long-term “skin disease”
• palpable abdominal mass
• weak with pale mm
• CBC: non-regenerative anemia, thrombocytopenia and leukopenia

Question 18

Adrenal associated endocrinopathy - Ferrets

Morph Diagnoses

Answer 18

• Adrenal cortical carcinoma/adenoma
• Diffuse myeloid and erythroid aplasia
• Prostatic cysts or diffuse cystic squamous metaplasia

Question 19

Adrenal associated endocrinopathy - Ferrets

Pathogenesis

Answer 19

• Bilateral adrenocortical hyperplasia or neoplasia (carcinoma > adenoma)
• excess production of estradiol
• Clinical signs:
• symmetrical alopecia, vulvar swelling, mammary gland hyperplasia
• Occurs more in animals neutered at an early age (2-4 months)
• Pancytopenia as a result of marrow aplasia (poorly understood)
• High levels of estrogen –> prostatic squamous metaplasia in males
• • dysuria may result from enlarged prostate

Question 20

Pheochromocytoma

Clinical Presentation

Answer 20

• Dyspnea
• acute onset blindness, bilateral mydriasis, hyphema of the eye
• tachyarrhythmias
• mild hyperglycemia (only chem abnormality)

Question 21

Pheochromocytoma

Morphologic Diagnoses

Answer 21

1, Adrenal carcinoma

• very aggressive, invasive
• tumor emboli are common –> lungs = dyspnea

2. Hypertrophic cardiomyopathy –> hypertrophy with dilation –> DCM
   - low grade catecholamine release impacts the heart
   - myocardial infarctions (small) –> tacchyarrhythmias

Question 22

Pheochromocytoma

Pathogenesis

Answer 22

• seen in cattle and dogs
• invasion into Vena Cave common with potential for tumor emboli
• Ca homeostasis implicated in development
• may result in retinal detachment
• cortisol and ACTH are often normal
  (unilateral tumor of the adrenals)

Question 23

Waterhouse-Friderichsen Syndrome

Answer 23

• Defined as adrenal gland failure due to bleeding into the adrenal glands
• occurs with Gram (-) endotoxemia = horses
• Diffuse necrosis of the adrenal glands
• Idiopathic pathogenesis

Question 24

Heart-base tumors

Answer 24

• often endocrine related
• especially in brachycephalic dogs (chronic hypoxic state)
  e. g. chemodectoma, hemangiosarcoma, ectopic thyroid tumor