Endocrine tumours in the guinea pig

• Signs and management of hyperthyroidism in guinea pigs appear very similar to those described in feline hyperthyroidism.
• An ACTH stimulation test utilizing saliva as a non-invasive sample matrix can be used to confirm hyperadrenocorticism.
• Trilostane can be used for the treatment of guinea pigs with hyperadrenocorticism.
• Insulinomas should be considered as possible differentials in guinea pigs with neurological signs.

Functional endocrine tumours have long been thought to be rare in guinea pigs, although conditions such as hyperthyroidism and hyperadrenocorticism have been documented with increasing frequency so the prevalence of hormonal disorders may have been underestimated. Both the clinical signs and diagnosis of hyperthyroidism in guinea pigs appear to be very similar to those described in feline hyperthyroidism, and methimazole has been proven to be a practical therapy option. Hyperadrenocorticism has been confirmed in several guinea pigs with an adrenocorticotropic hormone stimulation test using saliva as a non-invasive sample matrix; trilostane has been successfully used to treat a guinea pig with hyperadrenocorticism. Insulinomas have only rarely been documented in guinea pigs and one animal was effectively treated with diazoxide.