Pituitary tumor size, neurologic signs, and relation to endocrine test results in dogs with pituitary-dependent hyperadrenocorticism: 43 cases (1980-1990)

Barry S. Kipperman From the Veterinary Medical Teaching Hospital (Kipperman), and Departments of Veterinary Reproduction (Feldman), Pathology (Dybdal), and Medicine (Nelson), School of Veterinary Medicine, University of California, Davis, CA 95616.

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Edward C. Feldman From the Veterinary Medical Teaching Hospital (Kipperman), and Departments of Veterinary Reproduction (Feldman), Pathology (Dybdal), and Medicine (Nelson), School of Veterinary Medicine, University of California, Davis, CA 95616.

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Noel O. Dybdal From the Veterinary Medical Teaching Hospital (Kipperman), and Departments of Veterinary Reproduction (Feldman), Pathology (Dybdal), and Medicine (Nelson), School of Veterinary Medicine, University of California, Davis, CA 95616.

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Richard W. Nelson From the Veterinary Medical Teaching Hospital (Kipperman), and Departments of Veterinary Reproduction (Feldman), Pathology (Dybdal), and Medicine (Nelson), School of Veterinary Medicine, University of California, Davis, CA 95616.

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Summary

Pituitary neoplasm was identified in 43 dogs with pituitary-dependent hyperadrenocorticism via necropsy (n = 33), diagnostic imaging with computerized tomography or magnetic resonance imaging (n = 5), or diagnostic imaging and necropsy (n = 5). All dogs had clinical signs and clinicopathologic test results typical of hyperadrenocorticism. Thirty-seven dogs had grossly visible pituitary tumors, and 6 dogs had microscopic pituitary tumors. Fifteen dogs had developed neurologic signs typical of those resulting from an enlarging pituitary mass. Twenty-three dogs had pituitary tumors ≥ 1 cm in diameter. Provocative testing of the pituitary-adrenocortical axis was performed on all dogs.

Dogs with grossly visible pituitary tumors and dogs with neurologic signs had Significantly (P < 0.05) higher mean plasma endogenous acth concentrations, compared with values from dogs with microscopic tumors and dogs without neurologic signs, respectively. Dogs with grossly visible pituitary tumors and dogs with tumors ≥ 1 cm in diameter had Significantly (P < 0.05) lower adrenocortical responsiveness to exogenous acth, compared with dogs with microscopic pituitary tumors and dogs with tumors < 1 cm in diameter, respectively. Despite these differences, there was overlap between test results among dogs. On the basis of endocrine test results, it would appear difficult to distinguish dogs with pituitary-dependent hyperadrenocorticism and large pituitary tumors from those with pituitary-dependent hyperadrenocorticism and microscopic pituitary tumors prior to onset of neurologic signs.

Summary

Pituitary neoplasm was identified in 43 dogs with pituitary-dependent hyperadrenocorticism via necropsy (n = 33), diagnostic imaging with computerized tomography or magnetic resonance imaging (n = 5), or diagnostic imaging and necropsy (n = 5). All dogs had clinical signs and clinicopathologic test results typical of hyperadrenocorticism. Thirty-seven dogs had grossly visible pituitary tumors, and 6 dogs had microscopic pituitary tumors. Fifteen dogs had developed neurologic signs typical of those resulting from an enlarging pituitary mass. Twenty-three dogs had pituitary tumors ≥ 1 cm in diameter. Provocative testing of the pituitary-adrenocortical axis was performed on all dogs.

Dogs with grossly visible pituitary tumors and dogs with neurologic signs had Significantly (P < 0.05) higher mean plasma endogenous acth concentrations, compared with values from dogs with microscopic tumors and dogs without neurologic signs, respectively. Dogs with grossly visible pituitary tumors and dogs with tumors ≥ 1 cm in diameter had Significantly (P < 0.05) lower adrenocortical responsiveness to exogenous acth, compared with dogs with microscopic pituitary tumors and dogs with tumors < 1 cm in diameter, respectively. Despite these differences, there was overlap between test results among dogs. On the basis of endocrine test results, it would appear difficult to distinguish dogs with pituitary-dependent hyperadrenocorticism and large pituitary tumors from those with pituitary-dependent hyperadrenocorticism and microscopic pituitary tumors prior to onset of neurologic signs.

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