Chase, a 7-year-old Boston Terrier, was referred to our Internal Medicine service by his family veterinarian for management of multiple endocrine diseases. At presentation, he had poorly controlled diabetes mellitus, suspected (but unconfirmed) hyperadrenocorticism (Cushing’s disease), and a diagnosis of hypothyroidism.

Stabilizing the Initial Conditions

Following advanced diagnostics and adjustments to his treatment plan, Chase’s diabetes became significantly better controlled. He was formally diagnosed with Cushing’s disease (hyperadrenocorticism) and began treatment with trilostane.

At the time of referral, Chase had marked dermatologic changes, including severe skin disease and calcinosis cutis secondary to prolonged hypercortisolemia.

There was some uncertainty regarding his hypothyroidism diagnosis. Once his endocrine diseases were better controlled, Dr. Milaszewska elected to discontinue his thyroid medication and repeat testing. Repeat evaluation confirmed that Chase was not truly hypothyroid; rather, he had been experiencing euthyroid sick syndrome in the context of his concurrent illnesses.

An Unexpected Turn

Several months into treatment for Cushing’s disease, Chase presented to our Emergency Department with hematochezia and decreased appetite. Repeat bloodwork revealed a new and unexpected diagnosis: hypoadrenocorticism (Addison’s disease).

Although uncommon, this development occurred secondary to trilostane therapy. In rare cases, trilostane can contribute to adrenal necrosis, resulting in the opposite endocrine condition.

Ongoing Management & Outcome

Chase is now managed with monthly DOCP injections for Addison’s disease, along with a low maintenance dose of corticosteroids. His diabetes remains well controlled, and his clinical improvement at home has been remarkable — particularly the resolution of his dermatologic disease.

Chase’s case highlights the complexity of endocrine disorders and the importance of close monitoring, diagnostic reassessment, and individualized treatment adjustments. These conditions often require careful fine-tuning and ongoing collaboration between primary and referral teams.

We are grateful for the opportunity to work alongside his referring veterinarian in managing this challenging but rewarding case.