[A horse with Cushing’s disease].

The researchers performed a veterinary study on a thirteen-year-old Dutch warmblooded mare with sinusitis and concluded she had Cushing’s disease due to an adenoma (benign tumour) in a part of her pituitary gland, causing symptoms such as a potbellied appearance, dull coat with long hair and a suppressed response to the dexamethasone-suppression test.

Clinical Presentation and Initial Findings

• The horse, a thirteen-year-old Dutch warmblooded mare, presented with a dull coat, long wavy hair, and appeared thin and potbellied. These physical manifestations led the clinicians to suspect a possible abnormality.
• The mare was brought to the Faculty of Veterinary Medicine due to sinusitis (inflammation of the sinuses). Unilateral purulent nasal discharge, i.e., infection-related discharge from one nostril, made sinusitis evident.

Laboratory Tests and Results

• The mare was subjected to a complete blood count (CBC), which revealed leucopenia, or a low white blood cell count (3.9 G.L.-1).
• Plasma biochemical analysis showed high plasma glucose concentration (10.1 mmol.L-1), indicating possible metabolic disruption.
• The normal activity of the enzyme, thermostable alkaline phosphatase, could not be evidenced. This anomaly signaled a potential disorder.
• The mare’s basal (normal, resting level) plasma cortisol, a hormone released under stress, showed lowered concentration (114 nmol.L-1). This revealed that she was suffering from adrenocortical insufficiency, a condition of insufficient cortisol production.
• Moreover, her basal plasma ACTH (Adrenocorticotropic hormone, which stimulates the production of cortisol) concentration was significantly high (815 pg.ml-1), further indicating adrenocortical insufficiency.

Dexamethasone-suppression Test and Findings

• To validate the suspected condition, the mare underwent a dexamethasone-suppression test. 10 mg of dexamethasone was administered intramuscularly.
• Instead of the normal cortisol suppression of at least 50%, the mare’s cortisol levels were only suppressed by 32%. This response confirmed initial suspicions of an adrenocortical imbalance.

Necropsy and Final Diagnosis

• Upon necropsy, an adenoma (a type of benign tumor) was identified in the pituitary pars intermedia, a part of the pituitary gland. This finding explained all the previously observed symptoms and test results.
• Ultimately, this led to the diagnosis that the mare was suffering from Cushing’s disease, a condition caused by an overactive pituitary gland, typically due to a benign tumor like an adenoma.