Acromegaly

Question 1

Acromegaly

Answer 1

• Excess GH
• Overgrowth of bone and soft tissue

Question 2

GH secretion

Answer 2

• Controlled by negative feedback inhibition to Hypothalamus
• GH negatively feeds back on Pituitary and Hypothalamus
• Hypothalamus releases GHRH, stimulates Pituitary to release GH, goes to the liver and stimulates release of IGF 4
  
  • IGF 4 causes tissue growth

Question 3

Main Causes acromegaly

Answer 3

• Dogs: Progestins mainly
  
  • exogenous
  • Endogenous - females
  • Pituitary tumor (VERY RARE)
  • Hypothyroidism in dog can inc endogenous GH release
    
    • by decreasing pituitary somatostatin
• Cats: pituitary tumor only

Question 4

aside about hypothyroidism….

Answer 4

• Can make a dog make acromegalic
  
  • hypothyroidism can inc GH release by decreasing pituitary release of somatostatin
  • Boxer gone Mastif!

Question 5

Insulin resistence

Answer 5

• Insuline resistance at postreceptor sites
  
  • ​predisposes to Diabetes Mellitus
• All the cats will be diabetic

Question 6

Pathophys of GH secretion

Answer 6

• peripheral insuline resistance => hyperglycemia (DM)
• Inc in somatomedin C (IGF 1) => proliferation bone, cartilage, soft tissues

Question 7

GH can be _____

Answer 7

• Oncogenic

Question 8

Physical changes acromegaly

Answer 8

• gingival hyperplasia
• inc skin folds
• laryngeal hyperplasia and stridor
• enlarged maxilla, widening of teeth space
• protruding jaw

Question 9

Radiographic changes acromegaly

Answer 9

• inc oropharyngeal soft tissue
• Broadened metaphalanges
• windened interdental spaces
• inc head and limb soft tissue
• calvarium hyperostosis

Question 10

Clinical pathology acromegaly

Answer 10

• anemia or polycythemia
• mild hyperphosphatemia
• elevated alkaline phosphatase
• Elevated ALT
• +/- Hyperglycemia
  
  • most acromegalic cats are diabetic
  • some dogs are diabetic
• +/- glycosuria if diabetic

Question 11

Acromegaly DX

Answer 11

• Clinical features and PE
• IGF-1
• We don’t measure GH, but Europe does

Question 12

DM acromegaly cats are rarely

Answer 12

• ketoacidotic
  
  • enough insulin gets to liver to deter ketogenesis

Question 13

Feline Acromegaly signs

Answer 13

• PD/PU/Polyphagia => earliest sign
• Organ enlargement
  
  • liver, heart, tongue, kidneys
• Cardiomyopathy
• Lameness
• CNS dysfunction => Late sign from pituitary tum

Question 14

assoc pathology of acromegaly

Answer 14

• Pituitary tumor
• Myocardial wall hypertrophy
• Arthropathy
• Glomerulopathy

Question 15

Acromegaly Tx

Answer 15

• Iatrogenic => D/C progesterone TX
• Natural onset female dog => OHE
• Pituitary tumor => surgery/radiation
• no medical therapy
• give insulin as needed, if diabetic

Question 16

Acromegaly prognosis

Answer 16

• Dog => good
• Cat => poor