Ask a vet: Treating Cushing's disease in dogs

Cushing’s disease – or hyperadrenocorticism – is one of the most common hormonal disorders seen in middle-aged and older dogs.

It can be a confusing condition for owners, with its slow, subtle onset and wide range of possible symptoms. A little extra thirst here, a little more protruding tummy there, perhaps some thinning hair or a change in behaviour, all things that might be mistaken for a dog “just getting older.”

However, behind these signs lies a very real imbalance in the adrenal glands, one that can affect your dog’s quality of life if left unrecognised. 

Breeds prone to Cushing’s

Small breeds are more prone to pituitary-dependent Cushing’s (the most common form), while larger breeds may be more prone to adrenal tumour–related Cushing’s. Most cases appear in middle-aged to older dogs, usually over seven years of age, with these breeds often most susceptible:

• Poodle (especially Miniature and Toy)

• Dachshund

• Boston Terrier

• Boxer

• Beagle

• Yorkshire Terrier

• Maltese

• Staffordshire Bull Terrier

• Australian Shepherd

• German Shepherd

• Terriers in general (e.g., Jack Russell, Scottish Terrier, West Highland White Terrier)

Our consultant vet Dr Nick Thompson will explore the condition from both a conventional and holistic perspective.

Canine Cushing's disease

Canine Cushing's disease, known as hyperadrenocorticism (HAC), is characterised by the overproduction of cortisol hormone by the adrenal glands perched just above each kidney (hence, 'ad-renal').

This relatively common hormonal imbalance can result from either a pituitary gland tumour (pituitary-dependent hyperadrenocorticism, PDH) or an adrenal gland tumour. 

Excess cortisol leads to a number of diverse health issues, similar to those seen if too much cortisone is given by a vet over too long a period. The vet-induced artificial disease is called iatrogenic hyperadrenocorticism. The word 'Iatrogenic' derives from the Greek 'Iatros', meaning doctor. 

Symptoms of Cushing's disease in dogs

Cushing's disease is named after Dr Harvey Cushing, a renowned neurosurgeon who first described the disease in a single human patient as recently as 1912.

Symptoms of Cushing's include: 

• Increased thirst and urination
• A pot-bellied appearance
• Muscle weakness
• Fatigue
• Hair loss
• Skin infections

Diagnosis of Cushing's disease in dogs

Diagnosis in dogs involves several steps. First, vets start with a thorough physical examination and medical history to identify symptoms consistent with Cushing's disease. 

Blood tests can give a strong indication if the dog has Cushing's. These are called screening tests. The most common initial tests include an ACTH Stimulation Test. (ACTH, adreno-corticotrophin hormone, is produced by the pituitary gland in the normal dog's brain. It acts to provoke cortisone production in the adrenals) 

The Stimulation Test measures cortisol levels before and after administering ACTH, which should stimulate cortisol production in healthy dogs but not significantly in those with Cushing's (because the adrenals are working hard to produce lots of cortisol, so can't produce much more when asked by the artificial ACTH). 

Other tests for Cushing's

Another test vets use at this early stage is the Low-Dose Dexamethasone Suppression Test (LDDST), but we don't have room to go into too much detail here. 

A high-dose dexamethasone suppression test or endogenous ACTH levels help differentiate between PDH and adrenal-dependent hyperadrenocorticism. This more advanced test allows the vets to determine if the disease is based in the adrenals or is coming from a pituitary tumour. Nowadays, ultrasound or MRI might also be used to visualize the adrenal or pituitary glands for tumours to help in tricky cases. (Neiger, 2018). 

Don't let the above make you think that diagnosing Cushing's in dogs is always black and white; it is not. There are, maybe 10% of cases where it is unclear if the patient is hyperadrenocorticoid and these cases can be tricky to work up to a definitive conclusion. 

The treatment of Cushing’s in dogs 

The treatment of Canine Cushing's Disease is mainly based on Trilostane (Vetoryl) in the UK. Vetoryl is an easy-to-give oral medication that inhibits cortisol synthesis in the adrenal gland. Regular monitoring via ACTH stimulation tests is crucial to adjusting doses, but treatments can be straightforward (Feldman, 2011).

Mitotane (Lysodren) was the relatively dangerous drug we used to use in the UK and is still, I believe, used in the USA. This risky drug ('do not handle if you are or might be pregnant') was generally superseded by the relatively safer Trilostane. It (mitotane) destroys parts of the adrenal cortex, reducing cortisol production. It, too, requires careful monitoring due to its narrow therapeutic window (Kintzer & Peterson, 1991).

There are surgical options for adrenal tumours, and surgical removal might be considered in some cases. However, this is less common due to the complexity of the procedure and potential complications (van Sluijs et al., 1995). Managing secondary conditions like diabetes mellitus, hypertension, or skin infections is also vital.

Homeopathics and Cushing's in dogs

Horses, especially ponies, get Cushing's quite a lot. As with dogs, we don't know why, but we must help these afflicted creatures. The good thing for dogs is that remedies have been used for years with our equine friends. 

So, if you have a dog with Cushing's and want to look at every avenue before committing to Vetoryl and/or herbs, contact a local veterinary homeopath. To find one, visit bahvs.net for a list of practitioners in the UK.

Canine Cushing's and herbs

The list of herbs that may help with tumours, adrenal health, and endocrine balance is extensive. Here are just a few known to be very practical and safe. 

Golden Rod (Solidago virgaurea) isn't just a beautiful plant (Mrs Grieve, in her Modern Herbal of 1931 notes that the leaves and flowers yield a yellow dye, and, when bruised, the herb smells like Wild Carrot!); its diuretic properties might help manage the fluid retention and excessive urination common in Cushing's. Golden Rod's anti-inflammatory effects could also alleviate some of the discomfort associated with this condition (Bradley, 1992). The generic name comes from solidare because the plant is known as a vulnerary, or one that 'makes whole.'

Vitex agnus-castus, commonly known as Chaste Tree Berry, has a long history in herbal medicine for its hormone-regulating properties. In the context of canine Cushing's disease, where cortisol levels are abnormally high, Vitex might play a role through its influence on the pituitary gland. By modulating the release of hormones (hence the sexually supressive name 'Chaste Tree'), Vitex may help normalize cortisol production, thereby addressing key symptoms. 

Herbs for supporting liver function

Milk Thistle Seed (Silybum marianum) is celebrated for its liver-protective and regenerative properties, primarily (but not solely) due to its active component, silymarin. The liver's role in hormone metabolism is critical. Milk Thistle could offer significant benefits. 

It supports liver function by enhancing detoxification processes and protecting liver cells from damage. This can be particularly advantageous in managing the metabolic disturbances associated with Cushing's, potentially aiding in the regulation of cortisol levels. The liver's health is pivotal in hormone regulation, making Milk Thistle genuinely helpful and supportive. (Flora, 1998).

Artichoke Leaf (Cynara scolymus) complements Milk Thistle by supporting liver and gallbladder function. It's a mild bitter; therefore, cholagogue and choleretic actions promote bile flow, potentially aiding in digestion through the breakdown of fats and the elimination of toxins, which could be beneficial in managing the metabolic aspects of Cushing's (Fintelmann, 1996). Good bile circulation is crucial to the microbiome, and the trillions of bugs found in the canine gut are intimately linked with nutrient absorption, mood, and immune function. 

Cleavers (Galium aparine, also known as Clivers, Goosegrass. Barweed and Hedgeheriff, to name a few) are traditionally used for their lymphatic and diuretic properties. Mrs Grieve notes, on a practical historical note, 'that we learn from Dioscorides that the ancient Greek shepherds of his day employed the stems of this herb to make a rough sieve [for milk]. Remarkably, Linnaeus reported the same use being made of it in Sweden, in country districts, as a filter to strain milk; the stalks are still used thus in Sweden [in the 1930s]'.

Galium assists in managing fluid balance and aiding kidney function, which is crucial for dogs dealing with the polyuria and polydipsia of Cushing's. Cleavers may also have a mild anti-inflammatory effect, potentially easing symptoms like skin irritation (Mills & Bone, 2000).

Herbs for supporting the skin

I call this next herb the JCB of the herb world for its action on the skin; Burdock Root (Arctium lappa) serves as a powerful detoxifier, helping cleanse unwanted substances, especially, as mentioned, in the outer tissues of the body and the dermis. 

Its equilibrating impact on blood sugar levels could be beneficial for Cushing's patients, where Diabetes Mellitus (sugar diabetes) is often a sequel to adrenal dysfunction. Burdock's support in liver function also helps in the body's hormonal regulation (Wulff-Tilford & Tilford, 1999).

Goat's Rue (Galega officinalis) is known for its hypoglycemic effects, which could be advantageous in controlling raised blood glucose due to persistently high blood cortisol. Hyperglycaemia can lead to diabetes, as a result, in canine Cushing's. By helping regulate blood sugar, Goat's Rue can contribute to a more stable metabolic environment, reducing inflammation, oxidation, and some of the disease's secondary complications (Atta-Ur-Rahman & Zaman, 1989).

Conclusion

Cushing's diagnosis is usually straightforward, but the treatment can be tricky. Whether you use conventional medicine, Vetoryl, homoeopathic medicine or the ancient art of herbs, skill, balance, and good observation are required. 

If in doubt, consult a vet proficient in the appropriate techniques. If you're lucky, you may find a holistic vet who can guide you through all three. 

Cushing's is a disease that, if caught early, can be very amenable to treatment. If in doubt, if your dog has any, even a hint of some of the symptoms above, get along to the vet for a diagnosis and get cracking with the most effective treatment for your dog. 

Herbal references:

• Atta-Ur-Rahman, & Zaman, K. (1989). Medicinal plants with hypoglycemic activity. Journal of Ethnopharmacology, 26(1), 1-55.
• Bradley, P. R. (1992). British Herbal Compendium: Volume 1. British Herbal Medicine Association.
• Fintelmann, V. (1996). Therapeutic profile and specific indications of artichoke leaf extract. Phytomedicine, 3(2), 173-178.
• Flora, K., et al. (1998). Milk thistle (Silybum marianum) for the therapy of liver disease. The American journal of gastroenterology, 93(2), 139-143.
• Mills, S., & Bone, K. (2000). Principles and Practice of Phytotherapy: Modern Herbal Medicine. Churchill Livingstone.
• Mrs Grieve, A Modern Herbal. Tiger Books, Jan, 1996.
• Wehrenberg, W. B. (2000). Vitex agnus-castus: a review of its traditional and modern uses. Alternative Medicine Review, 5(6), 531-537.
• Wulff-Tilford, M., & Tilford, G. L. (1999). Herbs for Pets: The Natural Way to Enhance Your Pet's Life. BowTie Press. 

Cushing's references 

• Behrend, E. N. (2015). Canine Hyperadrenocorticism. Veterinary Clinics of North America: Small Animal Practice, 45(6), 1087-1106.
• Behrend, E. N., et al. (2013). Diagnosis of spontaneous canine hyperadrenocorticism: 2012 ACVIM consensus statement. Journal of Veterinary Internal Medicine, 27(6), 1292-1304.
• Feldman, E. C. (2011). Trilostane Treatment of Canine Hyperadrenocorticism. Veterinary Clinics of North America: Small Animal Practice, 41(6), 1123-1131.
• Kintzer, P. P., & Peterson, M. E. (1991). Mitotane (o,p'-DDD) treatment of 200 dogs with pituitary-dependent hyperadrenocorticism. Journal of Veterinary Internal Medicine, 5(3), 182-190.
• Neiger, R. (2018). Cushing's Syndrome in Dogs. Veterinary Record, 183(15), 472.
• van Sluijs, F. J., et al. (1995). Results of adrenalectomy in 36 dogs with hyperadrenocorticism caused by adrenocortical tumour. The Veterinary Record, 137(7), 179-182.