Iatrogenic hyperadrenocorticism in a cat following a short therapeutic course of methylprednisolone acetate

Abstract

Iatrogenic hyperadrenocorticism (or iatrogenic Cushing's syndrome) is an adrenal disorder that may result from long-term administration of glucocorticoids for therapeutic purposes, most often given to treat allergic or immune-mediated disorders. Prolonged treatment with synthetic glucocorticoids can suppress hypothalamic corticotrophin releasing hormone and plasma adrenocorticotrophic hormone (ACTH), thus causing a functional inactivity of the adrenal cortex. The result is a clinical syndrome of hyperadrenocorticism but with basal and ACTH-stimulated plasma cortisol concentrations that are consistent with spontaneous hypoadrenocorticism (Addison's disease). Whilst iatrogenic hyperadrenocorticism is relatively frequent in dogs, the diagnosis of iatrogenic hyperadrenocorticism in cats is very uncommon because this species has been found to be remarkably resistant to prolonged administration of glucocorticoids. To the author's knowledge, there are only two published clinical cases of feline iatrogenic Cushing's syndrome. This report describes a case of iatrogenic hyperadrenocorticism in a cat, and shows how normalisation of the adrenal function was achieved with supportive treatment and withdrawal of glucocorticoid administration.

Fig 1.

The general appearance of the patient at presentation: the cat was grossly overweight (5.5 kg) with a pendulous abdomen (a) and poor condition of the coat (b).

Fig 2.

Dorso-ventral (a) and lateral (b) abdominal radiographs showing the presence of excessive peri-visceral fat, overfilled stomach, full bladder and a moderate hepatomegaly.

Fig 3.

The general appearance of the patient at re-examination (4 months later). The patient had lost 1.3 kg and was no longer considered to be overweight. The condition of the coat and the skin had ameliorated and muscle tone was normal.

Fig 4.

Results of the ACTH stimulation test carried out on the third day of hospitalisation (▴) and the day of re-examination of the patient (•, 4 months later). The test was performed by measuring plasma cortisol prior to, 30 and 60 min after im administration of 125 μg of tetracosactrin (Synacthen; CIBA).