Feline Growth Hormone Disorders Flashcards
What’s the cause of feline growth hormone deficiency?
congenital - unknown
acquired - anything that impairs anterior pituitary function: inflammatory, infectious, immune-mediated, traumatic/ iatrogenic, or neoplastic
How does a cat with Hyposomatotropism look like?
proportional dwarfism - if disproportional, may be due to other causes (ex. hypothyroidism, or more than just GH deficiency)
- retained deciduous teeth
- poor haircoat
- generalized weakness, lethargy, hypoglycemia
What are some ddx for proportional dwarfism in cats?
- hepatic disease (ex. shunts)
- malnutrition
- GI disease
- renal disease
- cardiac disease
- inappropriate expectation
How is hyposomatotropism diagnosed in cats?
using IGF-1
- direct testing for GH is not validated in cats
What are some drawbacks for IGF-1 testing for hyposomatotropism in cats?
there are other non-growth hormone deficiency causes of decreased IGF-1
ex. hepatic dysfunction, medication, small stature, lymphoma, renal disease, newly diagnosed diabetes mellitus
How is feline hyposomatotropism treated?
- there are no commercial product GH specific to cats – could develop antibody using porcine or human ones. It’s also $$$ and can develop diabetes mellitus
- if there is concurrent pituitary hormone deficiencies, that could be treated
- progestin to stimulate GH secretion from mammary doesn’t work in cats (vs it’s done in dogs)
How to treat for secondary feline hyposomatotropism?
usually the clinical are subtle once they are done growing, so no GH replacement is needed
but they tend to be at an increased risk for obesity - so watch the caloric intake
What’s the prognosis for feline primary hyposomatotropism?
poor – shorter lifespan, development of infections, degenerative, or neurological complications
What’s prevalence of feline hypersomatotropism?
18-32% of cats with diabetes mellitus
- should consider screening for IGF-1 with any newly diagnosed DM patients
What’s the cause of feline hypersomatotropism?
- organophosphate
- genetic AIP gene mutation (documented in people, suggestive in some cats)
What are some early signs of feline hypersomatotropism?
mostly associated with c/s due to diabetes mellitus –> PU/PD
- insulin resistance
- inappropriate weight gain – gaining weight despite poor glycemic control
What are some late signs of feline hypersomatotropism?
Phenotypic changes:
- upper airway stridor (up to 53%)
- increased head width, broad facial features, protruding lower jaw
How is feline hypersomatotropism diagnosed?
- IGF-1 concentration (should be elevated), also good for treatment monitoring post hypophysectomy (not sensitive enough for post RT) newly diagnosed DM patients with insulin deficiency may not have elevated IGF-1
- serum type 3 collagen peptide (PIIIP), since GH is involved in tissue growth
-Gherlin not useful - also elevated in DM, but good for monitoring response - CT/ MRI demonstration of enlarged pituitary note, microadenoma or acidophil hyperplasia won’t be seen as enlargement on imaging
What are the treatment options for feline hypersomatotropism?
- Surgery- hypophysectomy
- gold standard
- need to supplement with low dose hydrocortisone and leveothyroxine, and desmopressin acetate (can be d/c in most cats)
- GH replacement not needed - Medical therapy
- pasireotide –> suppresses somatotrpinoma
- can enter diabetic remission (25%)
- AE: mild GI signs, $$$ - Radiation therapy
- may not be able to reverse the endocrinopathy but can shrink a large tumour - treating the DM only
- not to increase insulin dose too quickly
- watch for Somogyi effect
- other consequences as arthropathies, CHF, and CKD
