Adenohypophyseal aplasia (dogs/cattle)
- 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
Hyperadrenocorticism (Cushing’s) - Clinical signs
- usually a disease of older dogs
- PU/PD
- alopecia/skin disease
- polyphagia/weight gain
- pot belly
- acute dyspnea –> puimonary thromboembolism
Hyperadrenocorticism (Cushing’s) - Clin Path
- Stress leukogram
- thrombocytosis
- mild hyperglycemia
- hypercholesterolemia
- marked elevation in ALP
Hyperadrenocorticism (Cushing’s) - Gross Pathologic Findings
- Adrenal glands
- Kidneys
- Pit gland
- Vessels (arteries)
- Liver
- Dermal condition
- 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)
Hypoadrenocorticism (Addison’s) - Clinical presentation
- Intermittent or waxing/waning signs
- Lethargy, collapse
- Commonly young adult dogs
Hypoadrenocorticism (Addison’s) - Clin Path
- Mild, non-regenerative anemia
- lack of a stress leukogram***
- Hypoglycemia
- Hyperkalemia
- Hyponatremia/hypochloremia
- Azotemia + minimally concentrated urine
- Na:K ratio is < 25:1
Hypoadrenocorticism (Addison’s) - Gross pathologic findings
Adrenocortical atrophy!
Hypoadrenocorticism (Addison’s) - Pathogenesis
- 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)
What is the key feature of hypoadrenocorticism
Lack of stress leukogram
Equine PPID - Causes (MD’s)
- Diffuse hypertrichosis
- Pituitary adenoma of the pars intermedia
- poorly formed sella turcica bone in the horse –> compression of pit gland - Laminitis
Equine PPID - Pathogenesis
- Idiopathic, age-related loss of dopamine inhibition
- Increase secretion of POMC derivatives (MSH, and ACTH to a lesser extent)
- Cortisol is a counter-regulatory hormone of insulin
- increased cortisol results in insulin resistance –> hyperglycemia
Feline acromegaly
- 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
Feline acromegaly - Clin Path
- Hyperglycemia
- Stress leuk + mild erythrocytosis
- Elevated liver enzymes
- Hyperphosphatemia w/out renal azotemia, mild proteinuria
- Marked glucosuria
Feline acromegaly - PE findings
- Oval shaped eyes
- Broadening of the maxilla
- large paws
Feline acromegaly - MD
- Pituitary acidophil adenoma –> very treatable with tumor irriadiation
- Diffuse islet cell degeneration with amyloidosis –> hyperglycemia
- Proliferative and sclerosing glomerulonephropathy –> proteinuria
Feline acromegaly - Pathogenesis
- Acquired excess of GH due to adenoma of the pituitary
- Uncontrolled diabetes is typical presentation
- GH mediated insulin resistance
- Beta cell exhaustion
Adrenal associated endocrinopathy - Ferrets
Clinical presentation
- long-term “skin disease”
- palpable abdominal mass
- weak with pale mm
- CBC: non-regenerative anemia, thrombocytopenia and leukopenia
Adrenal associated endocrinopathy - Ferrets
Morph Diagnoses
- Adrenal cortical carcinoma/adenoma
- Diffuse myeloid and erythroid aplasia
- Prostatic cysts or diffuse cystic squamous metaplasia
Adrenal associated endocrinopathy - Ferrets
Pathogenesis
- 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
Pheochromocytoma
Clinical Presentation
- Dyspnea
- acute onset blindness, bilateral mydriasis, hyphema of the eye
- tachyarrhythmias
- mild hyperglycemia (only chem abnormality)
Pheochromocytoma
Morphologic Diagnoses
1, Adrenal carcinoma
- very aggressive, invasive
- tumor emboli are common –> lungs = dyspnea
- Hypertrophic cardiomyopathy –> hypertrophy with dilation –> DCM
- low grade catecholamine release impacts the heart
- myocardial infarctions (small) –> tacchyarrhythmias
Pheochromocytoma
Pathogenesis
- 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)
Waterhouse-Friderichsen Syndrome
- 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
Heart-base tumors
- often endocrine related
- especially in brachycephalic dogs (chronic hypoxic state)
e. g. chemodectoma, hemangiosarcoma, ectopic thyroid tumor