Feline Cushing's Syndrome (Hyperadrenocorticism): Fragile Skin and Diabetes

Feline Cushing's syndrome (hyperadrenocorticism) is a devastating endocrine disorder driven by persistent excessive cortisol production by the adrenal glands. Unlike in dogs, feline hyperadrenocorticism is almost invariably entangled with severe insulin-resistant diabetes mellitus and the striking feline skin fragility syndrome, where the dermal collagen matrix breaks down so severely that the skin tears like wet paper upon gentle handling.

Sources

This guide is not a substitute for a vet.24h Emergency Vets

Veterinarian carefully examining the skin and pot-bellied abdomen of a cat with endocrine disease — Foto: Nekolife

In this guide

1. Pathophysiology: Cortisol Excess and Collagen Depletion

Glucocorticoid excess creates a severe hypercatabolic state. Prolonged hypercortisolemia induces marked hepatic gluconeogenesis while downregulating peripheral GLUT4 glucose transporters, creating profound insulin resistance.

Critically in cats, cortisol shuts down fibroblast proliferation and collagen synthesis within the extracellular dermal matrix. The skin rapidly atrophies to a translucent, fragile membrane lacking structural tensile strength.

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2. Primary Etiologies: Pituitary, Adrenal and Iatrogenic

Three etiologic forms are recognized:

Pituitary-Dependent Hyperadrenocorticism (PDH): Responsible for ~80-85% of spontaneous cases, driven by ACTH-secreting pituitary micro- or macroadenomas.
Adrenal Tumors (AT): Accounts for ~15-20% of spontaneous cases, comprising functional adrenal adenomas or carcinomas.
Iatrogenic Cushing's: Caused by prolonged administration of potent glucocorticoids (depo-medrol or oral dexamethasone) commonly used for feline allergic dermatitis or asthma.

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3. Hallmarks: Fragile Skin and Refractory Diabetes

The feline clinical picture is distinctive and dramatic:

*Extreme skin fragility (Feline skin fragility syndrome):* Large tears and avulsions occurring without significant bleeding during everyday handling, scruffing, or routine grooming.
Insulin-resistant diabetes: Cats requiring escalating insulin dosages (>1.5-2.0 U/kg/dose) without achieving glycemic control, accompanied by marked polydipsia and polyuria.
Pot-bellied appearance and severe muscle catabolism: Truncal muscle loss, marked weakness, and pendulous abdomen.
Curled ear tips: The cartilage at the tips of the pinnae thins and curls downward symmetrically.

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4. Diagnostic Endocrine Workup

Feline testing protocols diverge significantly from canine standards:

High-Dose Low-Dose Dexamethasone Suppression Test (LDDST): Cats require a 10-fold higher dose of dexamethasone (0.1 mg/kg IV) to achieve pituitary-adrenal suppression owing to low glucocorticoid receptor affinity.
Urine Cortisol-to-Creatinine Ratio (UCCR): Highly sensitive screening test to rule out hyperadrenocorticism if negative.
High-resolution abdominal ultrasonography: Accurately measures adrenal pole dimensions and detects vascular invasion into the caudal vena cava.

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5. Treatment Protocol & Gentle Nursing

Clinical management requires hyper-vigilant care:

Trilostano therapy: Reversibly inhibits 3-beta-hydroxysteroid dehydrogenase. Dosing in cats requires precise compounding (typically 1-2 mg/kg q12h) with close electrolyte monitoring.
Surgical Adrenalectomy: Curative for unilateral, non-invasive adrenal carcinomas/adenomas once diabetes is stabilized.
Atraumatic handling protocol: Elimination of neck collars, avoidance of subcutaneous skin-tenting injections, and the use of padded fleece bedding to prevent skin sloughing.

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Scientific Sources and References

Feldman, E. C., Nelson, R. W., Reusch, C., & Scott-Moncrieff, J. C. (2015). Canine and Feline Endocrinology, 4th ed. Saunders.
Valentin, S. Y., et al. (2014). Hyperadrenocorticism in cats: 30 cases. J Vet Intern Med, 28(2), 481-487.
Trotman, T. K., et al. (2013). Feline skin fragility syndrome. Compend Contin Educ Vet, 35(7), E1-E7.

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