Atypical Cushing’s, also called atypical hyperadrenocorticism, is a disorder that affects your pet’s endocrine system, which controls hormone levels in the body.

Imagine the endocrine system as a delivery service that sends hormones through the bloodstream to carry out various normal and necessary body functions. These hormones help regulate functions such as the immune system, inflammation, and the sleep/wake cycle, and support the body's response to stress.

The hypothalamus is known as the brain's control center. It signals the pituitary gland, also part of the brain, which then tells the adrenal glands to produce the hormone cortisol. Cortisol concentrations in the blood are normally tightly regulated to maintain a state of balance (homeostasis) within the body’s systems. Too much cortisol in the blood, chronically, is called Cushing’s disease (hyperadrenocorticism). It is important to acknowledge that there are many reasons that cortisol may be elevated, such as stress, sickness, and other factors.

Atypical Cushing’s is different. Blood cortisol levels are normal in this condition, but sex hormone levels are elevated. An elevation in blood cortisol levels is characteristic only of typical Cushing's. The adrenal glands produce an excess of different hormones in both disorders, but the symptoms are very similar.

Diagnosis

Both dogs and cats can get Atypical Cushing's, but it is much more common in dogs. This condition is one of the rarest forms of Cushing's disease, and the cause is unknown. One of the first clues that your dog has this disorder is how your pet looks or behaves. The affected pet may have a potbelly appearance with alopecia (hair loss) and increased thirst, urination, and appetite. They may also experience general weakness.

Endocrine tests used for typical Cushing’s are normal in these dogs; blood cortisol levels are not elevated. For confirmation of Atypical Cushing's, sex hormone levels are evaluated before and after giving medication to stimulate the adrenal glands. This helps show whether an excess of sex hormones are being produced. Imaging tools, such as ultrasound, are also used to assess adrenal gland size and tumor presence. 

Treatment

Treatment is tailored to each patient, depending on the cause of the hormonal imbalance. In many cases, the excess of hormones produced by the adrenal gland can be medically managed by suppressing its function. This form of medical management is not a cure for the disease, and in most cases, medical treatment is lifelong. Medications like trilostane may be prescribed to prevent the adrenal glands from overproducing hormones. Independent of the chosen treatment option, cortisol levels should be rechecked 10 to 14 days after starting medication to confirm your pet is on the most appropriate dose. Cortisol monitoring can then be scheduled every 3 months to ensure effective treatment.

If an adrenal tumor is identified as the cause of the disease and confirmed with advanced imaging, surgical removal may be recommended. In these cases, removal of the adrenal tumor can be curative. However, removal of a pituitary gland mass is more complex. Although this surgery could resolve atypical Cushing's disease, the pituitary gland is responsible for regulating the release of several other hormones. As a result, its removal would lead to the development of additional endocrine disorders, including hypothyroidism, Addison's disease, and diabetes insipidus.

Prognosis

Your pet’s prognosis is based on how well the condition and symptoms can be managed. With early detection and appropriate medical management, your pet can often live a happy and healthy life. It is important to understand that medical management typically requires lifelong medication. If an adrenal mass causing the disease is surgically removed, the prognosis is generally good and may be curative. However, the removal of a pituitary mass is more complex and carries a more guarded prognosis.