Hi X, No, old age is not a disease. However as ferrets get older they are prone to 3 big problems. At roughly 3-4 years of age, we start to see adrenal gland disease problems. The thin hair on the tail and rump are suggestive of adrenal gland problems in Glacier. As they reach 4-5 years of age, we start seeing insulinoma problems. The weight lose, and weakness in the rear legs are suggestive of an insulinoma causing low blood sugar levels (hypo- glycemia). As they reach 5 and above, we start seeing lymphoma problems. Again the weight lose and weakness in the rear legs could be from lymphoma. Thus it is time to do some testing to find out what is actually causing Glacier's problems. The easiest way to check for an insulinoma is to do a fasting blood glucose test (i.e., remove food for 4 hours then take a small blood sample to check his blood glucose level). Simple and inexpensive test! To test for lymphoma, I would due a CBC with a panel. This is a screening test that can sometimes find abnormal lymphocytes or abnormal lymphocyte numbers in the blood sample. Sometimes x-rays, ultrasound, lymph node biopsy, organ aspirate, and/or organ biopsy will be needed to diagnose lymphoma. Yes, it can get expensive to confirm lymphoma. Anyway, a fasting glucose is a good place to start, followed by a CBC and panel. Then additional testing as needed. I would also start treating his adrenal gland problem with Lupron (or melatonin). Many times adrenal gland disease will make a ferret lethargic and cause some muscle loss. Plus in males, adrenal gland problems can cause an enlarged prostate problem that can prevent him from urinating. This is painful and can be fatal. Better to prevent than to treat a prostate problem! Hope that helps, Jerry Murray, DVM PS yes, the age ranges are just general guidelines. Ferrets of any age can get lymphoma and young ferrets can have adrenal gland and insulinoma problems too. [Posted in FML issue 3484]