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18 Acromegaly

• Infection should be suspected in all acral disease and treat accordingly. One of the Client Education
lick lesions, especially when the surface is common causes of treatment failure in acral Behavioral modification
VetBooks.ir most important treatments of acral lick Technician Tips SUGGESTED READING
lick dermatitis is the inability to identify
ulcerated. Oral antibiotics are one of the
primary or perpetuating factors.
dermatitis.
Miller WH Jr, et al: Muller & Kirk’s Small animal
○ In one study, deep bacterial infection was
Saunders, pp 205, 650-653.
present in 94% of the lesions, with 48% of Patients may lick and chew intensely at the dermatology, ed 7, St. Louis, 2013, Elsevier
cases yielding multidrug-resistant bacteria. lesion if it is uncovered even briefly, causing
• Behavioral component is often secondary. severe tissue damage. Close monitoring of AUTHOR & EDITOR: Manon Paradis, DMV, MVSc,
DACVD
Investigate potential for underlying skin bandages and Elizabethan collars are essential.

Acromegaly Client Education
Sheet

BASIC INFORMATION • GH-induced insulin resistance often (cats), • Cats: A minority presents with CNS signs
although not always (dogs, some cats), leads due to an expanding tumor or with heart
Definition to diabetes mellitus failure due to myocardial changes.
The clinical consequences of exposure to excess Clinical Presentation • Dogs may develop skin folds around the
endogenous growth hormone (GH) head, neck, and extremities.
DISEASE FORMS/SUBTYPES
Synonym • Cats: excessive GH secretion by an adenoma Etiology and Pathophysiology
Hypersomatotropism is often used as a of somatotrophs of the pituitary gland • In cats and rarely in dogs, the excess GH
synonym, although strictly speaking, it refers • Dogs: almost always secondary to progestin- secretion is due to a tumor (usually adenoma)
to excess endogenous GH alone and not its induced GH production and secretion by of the pars distalis of the anterior pituitary
consequences. the mammary glands (somatotrophs).
○ Endogenous progesterone elevation (i.e., • In dogs, disease stems from progesterone-
Epidemiology diestrus, pregnancy) or progestin admin- induced GH secretion by mammary tissue.
SPECIES, AGE, SEX istration (e.g., for estrus suppression) can The progesterone may be endogenous
• Cats: middle-aged/older (mean, 10 years; induce mammary hyperplasia. (diestrus) or exogenous.
range, 2-17 years); male predominance ○ Can occur due to GH secretion by • Effects of GH are the same, whether secreted
• Prevalence among cats is higher than previ- malignant or benign mammary tumors from the pituitary or mammary tissue.
ously recognized, ranging from 1 in 6 to 1 ○ Rarely due to GH-secreting pituitary • Chronic GH excess has catabolic and ana-
in 3 diabetic cats. Nondiabetic cats can have adenomas bolic effects. GH results in elevation of
acromegaly. liver-derived insulin-like growth factor 1
• Dogs: older, unspayed females over- HISTORY, CHIEF COMPLAINT (IGF-1).
represented due to diestrus-induced GH • In diabetic acromegalic patients • Anabolic effects are almost entirely mediated
production ○ Polyuria, polydipsia, polyphagia (some- by IGF-1, which causes proliferation of bone,
times extreme polyphagia) cartilage, soft tissues, and viscera.
GENETICS, BREED PREDISPOSITION ○ Weight gain with good or poor diabetic • Catabolic effects: GH stimulates hepatic
• No breed predisposition proven; Maine coon control gluconeogenesis and promotes lipolysis.
cats might be overrepresented. ○ Other complaints related to diabetes Insulin antagonism occurs due to a decrease
• A polymorphism in the AIP gene has mellitus (p. 251) in insulin receptors and postreceptor
been associated with some cases; siblings • Dogs: clinical signs typically begin 3-5 weeks antagonism. Diabetes mellitus usually results.
with the polymorphism have been affected after estrus in nonpregnant bitches; owners
simultaneously. should be questioned about prior administra- DIAGNOSIS
tion of a synthetic progestin (e.g., megestrol
RISK FACTORS acetate). Diagnostic Overview
• Progestin administration (dogs) • Nondiabetic cats can present with myocardial • Serum IGF-1 measurement is an effective
• Being an unspayed female (dogs) thickening/heart failure, signs due to upper screening tool in cats and dogs.
• Environmental organohalogenated contami- airway thickening (stridor/stertor), or rarely, • Given the high prevalence of acromegaly
nant exposure (cats) central nervous system (CNS) signs due to among diabetic cats, screening of newly
• Having an affected sibling (cats) an expanding pituitary tumor. diagnosed diabetic cats is advocated by the
author.
GEOGRAPHY AND SEASONALITY PHYSICAL EXAM FINDINGS ○ If IGF-1 is above the reference range, it
In cats, geographic variation can be associated • In dogs and cats, acromegalic changes include is 95% certain the disease is present.
with cause (e.g., environmental contaminant broad facial features, big paws, diffuse thick- ○ IGF-1 can be falsely low (≈10% of cats)
exposure) as well as clinician willingness to ening of oropharyngeal soft tissues, stridor/ in untreated or newly insulin-treated
screen for the disease. stertor, protrusion of the mandible, widening diabetic cats (IGF-1 production requires
of interdental spaces, organomegaly (palpable sufficient insulin); re-test 6 weeks after
ASSOCIATED DISORDERS hepatomegaly, renomegaly, or splenomegaly, initiation of insulin therapy if suspicion
• Chronic excess GH causes tissue growth, murmur associated with cardiomegaly). for acromegaly remains.
eventually resulting in myriad changes in • Approximately 75% of cats have no pheno- • Screening for acromegaly should be con-
various body systems (see below). typic features specific to acromegaly. sidered in nondiabetic cats with cardiac

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