Small adrenal glands in cats with feline interstitial cystitis

Purpose: We documented the uncoupling of sympathetic nervous system activity from the hypothalamic-pituitary-adrenal axis in cats with feline interstitial cystitis (FIC). Altered hypothalamic-pituitary-adrenal activity was recently suggested in some humans with interstitial cystitis (IC) but to our knowledge no information exists on adrenal gland size and histopathology in this disease. To investigate further adrenal function in cats with FIC we determined cortisol responses to 125 mug synthetic adrenocorticotropic hormone (ACTH) as well as adrenal size and histology. Materials and Methods: ACTH stimulation studies were performed in 11 healthy cats and 20 with FIC. Adrenal glands obtained at autopsy in 8 healthy cats and 13 with FIC were weighed, measured and examined histologically. Results: Cats with FIC had significantly decreased responses to ACTH (2-way repeated measures ANOVA p <0.05). Mean weight +/- SD (58 +/- 50 vs 241 +/- 60 mg) and volume (264 +/- 72 vs 410 +/- 115 mm(3)) in of adrenal glands were significantly smaller in cats with FIC than in healthy cats (p <0.05). Conclusions: These results suggest that cats with FIC may have mild primary adrenal insufficiency. Decreased adrenal size has been observed in patients with chronic fatigue syndrome, which can be a co-morbid condition in some patients with IC. If these abnormalities are confirmed in humans with IC, hormone replacement therapy may be indicated in select patients.