Diagnosis of Adrenal Disease in Ferrets
In ferrets, adrenal disease is mainly an adrenal dependent disorder that appears to be linked to high circulating gonadotrophin levels. Research has illustrated an association particularly with neutering in ferrets, with a temporal correlation between the time of neutering and the time of diagnosis of adrenal disease established. Lack of functional feedback on hypothalamic Gonadotrophin Releasing Hormone (GnRH) in neutered ferrets results in persistently elevated gonadotrophin levels, including Luteinizing hormone (LH). It is thought this may lead to excessive stimulation of LH receptors in the adrenal cortices of ferrets, adrenocortical hyperplasia and ultimately to tumour transformation. In entire ferrets, clinical signs of adrenal disease are usually seen in the breeding season when plasma gonadotrophin levels are high.
There is a high prevalence of adrenal cortical disease in ferrets in the USA, associated with the practice of spaying and neutering at an early stage. In the UK, adrenal tumours in ferrets historically have been rarely reported, although the frequency of diagnosis appears to have increased in recent years.
Affected ferrets tend to develop progressive symmetrical alopecia, usually starting on the rump, tail or flank, which may lead to complete baldness in as little as 5 weeks. In entire animals, hair may regrow outside the breeding season, only to be lost again the following spring. Pruritis is common. Females may have enlarged vulvas and a seromucoid vaginal discharge, and males may develop prostatic enlargement leading to dysuria, stranguria or anuria. Occasionally, the enlarged adrenal gland is palpable and ultrasonography may help in this assessment, although this is not an easy procedure to perform.
Haematology parameters are within normal limits, although rarely an anaemia may be present. In some severe cases, pancytopenia may be seen, as with oestrogen induced bone marrow toxicity. Serum biochemistry is usually within normal limits although occasionally ALT may be elevated. Blood glucose levels always should be checked, as some ferrets with adrenal disease may have concurrent insulinoma.
ACTH stimulation and LDDS tests are not indicated in ferrets where adrenal disease is suspected, as high cortisol levels are not a feature of the disease.
A number of steroid hormones tend to be abnormally elevated in ferrets with adrenal disease and their measurement is believed to be one of the most reliable means of diagnosing the condition. This has led to the development of Greendale's Ferret Adrenal Profile, which includes oestradiol, 17-hydroxyprogesterone and cortisol.
1ml serum. Basal samples only are required.