New Study Identifies Key Risk Factors for Pituitary Macrotumors in Dogs With Cushing’s Disease

Risk Factors for Pituitary Macrotumor in Dogs With Hypercortisolism

Kei Yoshida, Yui Kobatake, Satoshi Takashima, Naohito Nishii

Background

Hypercortisolism (Cushing’s disease) in dogs is most commonly caused by pituitary-dependent hypercortisolism (PDH). Pituitary macrotumors, large adenomas of the pituitary gland, can produce both endocrine and neurologic signs due to mass effect. However, advanced imaging is required to diagnose these tumors, which is costly and not always feasible. Identifying easily observable clinical predictors could help determine which dogs should undergo pituitary imaging.

Methods

This retrospective study analyzed 130 dogs with PDH seen at Gifu University Animal Medical Center (2012–2022). Inclusion criteria were confirmed hypercortisolism through endocrine testing (ACTH stimulation or low-dose dexamethasone suppression) and pituitary imaging (CT or MRI). The pituitary height-to-brain area (P/B) ratio was measured; dogs with ratios ≥ 0.4 × 10⁻² mm⁻¹ were classified as having a macrotumor. Clinical and physical data, including age, breed, neurologic signs, and vital parameters, were extracted from records. Univariate and multivariate logistic regression analyses were performed to identify independent predictors of pituitary macrotumor.

Results

Of 130 dogs, 54 (41.5%) had pituitary macrotumors. Dogs with macrotumors were significantly younger (median = 9.9 years) than those with microtumors (median = 11.7 years; p < 0.0001). Neurologic signs were present in 69% of macrotumor cases versus 25% of microtumor cases (p < 0.001), with depressed mentation and seizures being most strongly associated. French Bulldogs were disproportionately affected, comprising 28% of macrotumor cases but 5% of microtumor cases. Multivariate logistic regression identified three independent risk factors for macrotumor:

-Age at diagnosis ≤ 10.9 years (OR = 0.718; p < 0.05)

-French Bulldog breed (OR = 21.0; p < 0.01)

-Presence of neurologic signs (OR = 10.9; p < 0.001).

Other factors, including body temperature and treatment duration, were not significant.

Limitations

The study’s retrospective nature limited standardization of clinical assessments and imaging timing. Breed-specific analyses were restricted by sample size, and some subtle neurologic signs might have been missed. Only single-timepoint imaging was available, precluding evaluation of tumor progression. Comorbidities potentially influencing temperature or heart rate were not excluded.

Conclusions

Younger dogs (≤ 10.9 years), French Bulldogs, and those presenting with neurologic abnormalities have a markedly increased risk of pituitary macrotumor in PDH. The findings support targeted use of pituitary imaging in these high-risk groups to guide diagnosis and treatment decisions. This risk-based approach could improve early detection and management of pituitary macrotumors in dogs with Cushing’s disease.

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