Acromegaly and DI

Question 1

Basic definition of acromegaly

Answer 1

Excess GH causes overgrowth of bone and soft tissue.

Also causes peripheral insulin resistance, and possible DM.

Question 2

Main causes of acromegaly

Answer 2

Dogs: Progestins mainly.
-exogenous
-endogenous (females)
-pituitary tumor VERY rare.
-hypothyroidism in dogs (^GH, b/c of decreasing pituitary somatostatit)
Cats: pituitary tumor only.

Question 3

Radiographic changes seen with acromegaly.

Answer 3

Increased oropharyngeal soft tissue.
Broadened metaphalanges.
Widened interdental spaces.
Increased head and limb soft tissue.
Calvarium hyperostosis.

Question 4

Acromegaly clin path

Answer 4

anemia or polycythemia
mild hyperphosphatemia
^ALP/ALT
\+/- hyperglycemia
\+/- glycosuria

Question 5

Most common clinical finding in feline acromegaly is?

Answer 5

Insulin-resistant DM.

Note: DKA is rare, because enough insulin gets to liver to prevent ketogenesis.

Question 6

Feline acromegaly s/s

Answer 6

PU/PD/polyphagia
Organ enlargement (liver, heart, tongue)
Cardiomyopathy
Lameness
CNS dysfunction seen late.

Question 7

Acromegaly - associated pathology

Answer 7

Pituitary tumor
myocardial wall hypertrophy
arthropathy
glomerulopathy

Question 8

Tx of acromegaly

Answer 8

Iatrogenic - d/c progesterone rx’s, or OVH.
Pituitary tumor - Sx or radiation.
NO MEDICAL THERAPY.
Give insulin PRN if diabetic.

Question 9

Acromegaly prognosis

Answer 9

Dogs - good

Cats - poor long term

Question 10

Two types of diabetes insipidus

Answer 10

Central and nephrogenic

Central is pituitary dependent, and when given the ADH/vasopressin test urine will become concentrated.

Question 11

Diagnostic criteria for DI

Answer 11

Hx of PU/PD
Normal PE
Normal chemistries
hyposthenuria <1.008

To test: water deprivation test, vasopressin test, or ADH trial.

Question 12

How do you treat central DI?

Answer 12

DDAVP nasal drops, applied to the eye.
*1-4 drops topically to conjunctiva SID-BID. Costly…

DDAVP tablets: available as 0.1 and 0.2mg tabs. Sometime effective. Give 0.1 mg PO TID and titrate to effect.

Question 13

How do you tx nephrogenic DI?

Answer 13

Chlorothiazide 20-40 mg/kg BID and low sodium diet.

Question 14

Incidence of pituitary dwarfism

Answer 14

Affects german shepherd, and other breeds. Simple autosomal recessive.

Neck of rathke’s pouch constricted by growth of mesoderm.

Question 15

What are the lab abnormalities seen with dwarfism?

Answer 15

*Decreased:
Basal GH
GH post clonidine
IGF1
Basal T4
Gonadotropin
Prolactin
*Increased: insulin sensitivity.
NORMAL CORTISOL.

Question 16

Tx of dwarfism

Answer 16

GH 0.3 IU/kg/wk or 2 units q2d x 4-6 weeks.
Prefer porcine GH. Benefits restricted to skin only.
Thyroxine 0.02 mg/kg SID.
Medroxyprogesterone acetate, but beware of side effects.