Acromegaly in cats

Acromegaly is the term used in human medicine to describe a condition resulting from chronic excessive growth hormone (GH) secretion. The word acromegaly derives from the Greek noun ‘akros’ meaning extremity and affix ‘megaly’ meaning abnormal enlargement. Acromegaly can result in gigantism in humans if the condition occurs before growth plate closure, however it is most commonly diagnosed in middle-aged and older humans when it results in increased soft tissue and bone growth without gigantism. The term hypersomatotropism (HST) rather than acromegaly may be appropriate when describing the condition resulting from chronic excessive GH secretion in cats because growth hormone-induced enlargement is more difficult to identify in adult cats.

The first description of HST in cats was in 1976 (Gembardt and Loppnow, 1976). The estimated prevalence of diabetes mellitus (DM) in the insured UK cat population was 1 in 230 cats in 2003 and feline HST appears to be the cause of DM in up to 25% of diabetic cats (McCann et al, 2007; Schäfer et al, 2014; Niessen et al, 2015). However, feline HST is considered to be an underdiagnosed endocrine disorder in the UK which was highlighted by the results of one study which reported three quarters of veterinarians did not suspect HST when cats were highly likely to be affected by the condition (Niessen et al, 2015).