Feline Acromegaly: An Underdiagnosed Endocrinopathy?

Abstract

Background: Feline acromegaly has been reported infrequently in the veterinary literature and current knowledge of this endocrinopathy is based on limited numbers of animals with relatively advanced clinical signs. Hypothesis: This study was undertaken to screen diabetic cats for the presence of acromegaly. Animals: Diabetic cats with variable control examined by general practitioners in the United Kingdom. Methods: Blood samples were screened for the possible presence of acromegaly with basal serum concentrations of insulinlike growth factor 1 (IGF‐1) and, when available, feline growth hormone (fGH). In patients with markedly increased IGF‐1 concentrations intracranial computed tomography (CT) was offered, and in selected cats additional imaging was performed. Results: IGF‐1 was determined in 184 variably controlled diabetic cats; 59 cats had markedly increased IGF‐1 concentrations (.1,000 ng/mL; reference interval, 208–443 ng/mL). Eighteen cats subsequently were examined, and acromegaly was confirmed in 17 cats. Notable findings included absence of a detectable pituitary mass lesion in some affected cats regardless of whether CT or magnetic resonance imaging (MRI) was used. Hypertension was not found to be a complication in the evaluated cats and respiratory stridor was more prevalent than previously reported. Conclusions and Clinical Importance: Measurement of IGF‐1, growth hormone (GH), or both is useful in the diagnosis of acromegaly in cats.

Computed tomographic signs of acromegaly in 68 diabetic cats with hypersomatotropism

“…[1][2][3] Hypersomatotropism is increasingly recognised in cats. [4][5][6][7][8][9] As in humans, this is usually the result of a functional pituitary tumour. Excessive growth hormone causes various metabolic effects, including increased production of insulin-like growth factor-1 (IGF-1) predominantly by the liver.…”

Pharmacological treatment with cabergoline in three cats with acromegaly

“…In Case 1, IGF-1 was slightly below the cut-off value (>1000 ng/mL) established by Niessen et al (2007) for AMG diagnosis in cats, but considerably higher than that in non-acromegalic cats with DM (208-443 ng/mL) according to the same author. This suggests that many cats with AMG are likely to undergo subclinical stages with minor physical manifestation and subtler MRI findings than those presenting truly high IGF-1 levels.…”

“…This suggests that many cats with AMG are likely to undergo subclinical stages with minor physical manifestation and subtler MRI findings than those presenting truly high IGF-1 levels. This reasoning is based on findings by Niessen et al (2007) and Peterson et al (2007) for acromegalic cats phenotypically indistinguishable from normal cats, without detectable pituitary masses in the MRI, probably due to microadenomas or pituitary hyperplasia (Niessen et al, 2007;Lonser et al, 2010;Khandelwal et al, 2011;.…”

“…Thyroxine, reference value (RV): 1-3 µg/dL (Chemiluminiscence-CLM); Free thyroxine, RV: 0.6-1.6 ng/dL (CLM); UCCR: Urine cortisol creatinine ratio, RV: <10 x 10 -6 , nonspecifi c feline Cushing syndrome (FCS): 10-36 x 10 -6 , diagnosis FCS: >36 x 10 -6 ; IGF-1: Insulin-like growth factor 1, RV cats with diabetes mellitus: 208-443 ng/mL, cats with acromegaly >1000 ng/mL (Niessen et al, 2007), CLM; Fructosamine, RV: <322 µmol/L (Niessen et al, 2007) that pharmacological therapy should be initiated based on human medicine records. An oral dose of 10 µg/Kg Cbg every 72 h (Wanke et al, 2002) was prescribed, maintaining the same doses of insulin (Case 1: 7 U/cat, Case 2: 14 U/cat, Case 3: 9 U/cat) and their frequency (bid) in each cat.…”

Spontaneous Diabetes Mellitus in Animals

“…Acromegaly as consequence of pituitary acidophil adenoma results in excessive secretion of growth factor (GH) and also causes associated severe insulin resistance and diabetes mellitus [106]. The excess of GH will generate further synthesis of insulin growth factor 1 (IGH-1) which exerts anabolic effect and subsequent proliferation of connective tissue, cartilages, bones, and organs.…”