At age 8 or 9, the cause of your boy's enlarged spleen could be almost anything. Or there could be no direct cause at all. Enlarged spleens are fairly common as ferrets get older, and especially at that age. It's unlikely that it's related to Lupron or Deslorelin, and may or may not have anything to do with the adrenal disease. What you should be aware of is that your boy's declining quality of life is probably due to the adrenal tumor or tumors becoming larger and more of a problem. You have been treating them for a long time, and they have continued to grow during that time. Eventually they do become too much for even a Deslorelin implant to fight against effectively. My guess would be that he's feeling pretty lousy over all as a result of the adrenal disease, and that his enlarged spleen is a by-product of that. If he hasn't had a Deslorelin implant within 5 or 6 months, I'd get him another. If he has, I'd get him a very strong Lupron Depot shot, like at least 1.0 mg. I'm just suggesting what I would do if he was my ferret... you should of course discuss this with your vet. But also at age 8 or 9 you will soon need to consider palliative care if his over all health continues to decline. He's had a full life and you've obviously taken good care of him! Jeff Caring for Boomer, Zoomer, Gemini, Bella, Pinky, Simba, & Nala In memory of Luna, Neo, Sweet Sylvie, Baby Girl, Dozer, Morphy, Trinity, Sabrina, Minnie Mouse, Pop, Pip, Possum, Hunny, Mr. Parker, Misty, Frodo, Baggins [Posted in FML 7955]