Cushing's disease in dogs: treatment and evidence

What is Cushing's disease?

Cushing's disease, medically called hyperadrenocorticism (HAC), is the most diagnosed adrenal cortex disorder in the dog [2]. The adrenal cortex produces too much cortisol. In 80–85% of cases, the cause is an ACTH-producing tumour in the pituitary gland (pituitary-dependent Cushing); in 10–15% the tumour is located in the adrenal gland itself [2].

Recognition: typical symptoms

• Excessive drinking and excessive urination (polydipsia/polyuria)
• Excessive appetite
• Pendulous, distended abdomen
• Symmetrical hair loss, thin skin
• Excessive panting
• Muscle weakness and muscle atrophy
• Elevated blood pressure

Diagnosis and conventional treatment

Diagnosis requires blood testing (ACTH stimulation test or low-dose dexamethasone suppression test) and imaging (adrenal cortex ultrasound, possibly pituitary MRI) to distinguish between the two forms [2].

Trilostane (Vetoryl) is the only FDA-approved medical treatment for both forms in dogs [3]. Mitotane is an alternative; for adrenal tumours, surgery is an option. Treatment requires lifelong monitoring — the ACTH stimulation test determines whether the dosage is still correct [3].

What does the evidence say about natural options?

Melatonin and lignans

In holistic circles, melatonin and lignans (from flaxseed) are recommended, particularly for so-called 'atypical Cushing' where sex hormones are elevated without classical cortisol-Cushing. However, the evidence is extremely weak:

• The only direct research is an in-vitro study on human adrenal tumour cells [1] — no laboratory animals, no dogs, no clinical setting.
• There is no controlled clinical study in dogs demonstrating that melatonin or lignans lower cortisol, improve symptoms or slow the disease [1][3].
• The AAHA 2023 guideline for endocrinopathies in dogs and cats does not list these agents as recognised treatment options for classical hyperadrenocorticism [3].
• The claims are based on anecdotal reports and extrapolation from a single laboratory experiment.

Conclusion: There is no clinical evidence that melatonin or lignans work for Cushing's disease in the dog. Self-treatment with these agents in classical hyperadrenocorticism is dangerous: untreated or undertreated Cushing's leads to serious complications such as diabetes mellitus, high blood pressure, pulmonary thrombosis and recurrent infections [2].

Diet and lifestyle

There are no controlled studies showing that a specific diet influences the progression of hyperadrenocorticism. A balanced, quality diet supports general health but does not replace medical treatment.

Supplementary ≠ alternative

Cushing's disease is a progressive condition with a predictable list of complications if left untreated. Supplementary agents may — if a veterinary surgeon does not explicitly advise against them — be considered alongside conventional treatment for welfare support, but never as a replacement for trilostane or other proven therapies.

Always discuss any supplementary agent with the treating veterinary surgeon, also because some supplements can affect the accuracy of diagnostic tests.