pituitary pars intermedia dysfunction (ppid) bonnie brenseke, dvm anatomic pathology resident...

Pituitary Pars Intermedia Dysfunction (PPID)

Bonnie Brenseke, DVMAnatomic Pathology ResidentVirginia Maryland Regional

College of Veterinary Medicine

Authors: Bonnie Brenseke, Tanya LeRoith, and Geoff SaundersContributors: Mark Crisman and Jamie Wearn

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“Kibbles”

*not really “Kibbles”, hoofcare.blogspot.com

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For the washer/dryer and free trip to Hawaii…

• Classic case of PPID/Equine Cushing’s Syndrome

• Common endocrine disorder of aged horses and ponies

• Etiology and pathophysiology?

-primary lesion of the pituitary gland

-loss of dopaminergic inhibition on the pars intermedia

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Anatomy:

Banks, William. Applied Veterinary Histology. Baltimore, MD: Williams & Wilkins, 1981.

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Pathogenesis:

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Clinical Signs due to hormone dysregulation & to space-occupying effects

• Hypertrichosis (Hirsutism)- almost pathognomonic

• Hyperhydrosis

• Laminitis

• Polyuria/Polydipsia

• Polyphagia

• ↑’ed susceptibility to infections (skin, lung, parasites)

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Clinical signs cont’d

• Behavioral changes-docility, lethargy, narcolepsy

• Muscle wasting- pendulous abdomen, sway back

• Fat redistribution- bulging supraorbital fat pads, cresty neck, fat accumulation around tailhead

• Infertility

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Diagnostics:

• CBC/Chem/UA• Dexamethasone Suppression Test (DST)-fail to

suppress cortisol (> 1μg/dl)• ACTH levels- >50pg/ml in horses and >27pg/ml

in ponies supports diagnosis

• Baseline cortisol concentrations• Urinary corticoid/creatinine ratio• ACTH stimulation test• Combined DST and ACTH stimulation test• Thyrotropin-releasing hormone (TRH) stimulation test• Combined DST and TRH stimulation test• Resting insulin concentrations• Glucose tolerance test• Insulin tolerance test• Imaging

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Treatment:

• Dopamine agonists Pergolide and Bromocriptine

• Serotonin antagonist Cyproheptadine

• Supplements Magnesium & chromium picolinate Vitex (chasteberry extract, V. agnus-castus)

*Treat all pathologic conditions (i.e., laminitis & infections)

www.smartpakequine.com

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Necropsy findings:

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Pituitary Adenoma

Histopathology:

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Miller, M.A., I.D. Pardo, L.P. Jackson, G.E. Moore and J.E. Sojka. “Correlation of Pituitary Histomorphometry with Adrenocorticotrophic Hormone Response to Domperidone Administration in the Diagnosis of Equine Pituitary Pars Intermedia Dysfunction.” Veterinary Pathology 45 (2008): 26- 38.

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Ultrastructural Findings:

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References:

1. Banks, William. Applied Veterinary Histology. Baltimore, MD: Williams & Wilkins, 1981.

2. Capen, Charles. “Tumors of the Endocrine Glands.” Tumors in Domestic Animals. Ed. Donald Meuten. Ames, IA: Iowa State Press, 2002. 616-620.

3. McFarlane, D., M.T.Donaldson, T.M. Saleh and A.E. Cribb. “The Role of Dopaminergic Neurodegeneration in Equine Pituitary Pars Intermedia Dysfunction (Equine Cushing’s Disease).” Proceedings of the 49th Annual Convention of the American Association of Equine Practitioners, New Orleans, Louisiana, USA, 21-25 November 2003. Internet Publisher: International Veterinary Information Service.

4. Miller, M.A., I.D. Pardo, L.P. Jackson, G.E. Moore and J.E. Sojka. “Correlation of Pituitary Histomorphometry with Adrenocorticotrophic Hormone Response to Domperidone Administration in the Diagnosis of Equine Pituitary Pars Intermedia Dysfunction.” Veterinary Pathology 45 (2008): 26- 38.

5. Toribio, Ramiro. “Pars Intermedia Dysfunction (Equine Cushing’s Disease).” Equine Internal Medicine. Ed. Liz Fathman. St. Louis, MN: Saunders, 2004. 1327-1338.

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BIG Thanks to:• Pathologists: Drs. Tanya LeRoith &

Geoff Saunders

• Equine Clinicians: Drs. Mark Crisman & Jamie Wearn

• Resident Mates: Drs. Natalie Durrett, Anya Hawthorn, & Ron Tyler

• Histology Laboratory Technicians: Barbara Wheeler, Jill Songer, & Luther Vest

• Morphology Laboratory Manager: Kathy Lowe

• Media: Jerry BaberPresented at SEVPAC 2008 – Permission granted for use on

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Go Pack! Go Hokies!

QUESTIONS?

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