Endocrine disease in guinea pigs: a review on hyperthyroidism

Although hyperthyroidism condition has been increasingly reported in guinea pigs, it remains underdiagnosed because of the lack of publications on its causes, diagnostic methodologies and treatment options (Gibbons et al, 2013; Pignon and Mayer, 2013; Girod-Rüffer et al, 2019). Diagnostic assays have also not been validated and the effects of therapeutic modalities have not been studied sufficiently (Brandão et al, 2013).

Hyperthyroidism or thyrotoxicosis has been documented in several species and it is the most common endocrinopathy in cats (Brandão et al, 2013). While in humans it is most commonly caused by the autoimmune condition Graves' disease (Brandão et al, 2013), in guinea pigs the reported causes are functional unilateral or bilateral thyroid neoplasia (Edis and Pellett, 2019) and excess secretion from ectopic thyroid tissue (Kondo et al, 2018). In a study by Gibbons et al (2013) thyroid tumours were among the most common neoplasias found in laboratory guinea pigs, although it was not established whether the affected animals actually had hyperthyroidism. While in feline medicine hyperthyroidism secondary to a primary thyroid stimulating hormone (TSH)-secreting pituitary tumour has been described (Gordon et al, 2003), to the author ‘s knowledge no documentation on its occurrence in guinea pigs currently exists.