I think there is some confusion with Lupron because it is in a relatively new class of drugs, and real new to most vets. It is not a drug that we use in dogs and cats. Mostly it is used in ferrets and in birds (chronic egg layers).
In people, it is used for uterine leiomyomata (fibroids), endometriosis, endometrial stromal sarcoma, breast cancer (especially in pre menopausal females), poly cystic ovarian disease, functional bowel disease (progesterone related irritable bowel syndrome), prostate cancer, and giant multilocular cyst adenoma of the prostate (very similar to the pro static cysts in ferrets).
These are diseases that are hormone responsive (i.e. a hormone(s) stimulates the tissue to grow). If you take away the hormone(s), the tissue no longer grows and most will regress with time (i.e. take away the hormone and the tissue gets smaller). This has been documented in people with uterine fibroids, endometriosis, endometrial stromal sarcoma, breast cancer, ovarian cancer, poly cystic ovarian disease, prostate cancer, and cyst adenoma of the prostate. It has also been documented in rats with prostate cancer and mammary cancer. It has also recently been documented in ferrets with adrenal gland disease! It is sort of like turning off a light switch. Electricity no longer stimulates the light bulb. The light bulb no longer produces light. In ferrets, Lupron is like that light switch. It turns off LH. LH no longer stimulates the adrenal gland. The adrenal gland(s) no longer produces the sex hormones.
In cases of adrenal hyperplasia and adenomas, they are not likely to spread or get big enough to cause any "space occupying mass" problem. Only carcinomas will grow into those large tumors. Usually only the right gland is going to spread to the liver and mainly when that gland becomes big. Thus for cases of adrenal hyperplasia and adenomas, stopping the stimulation with Lupron, stops the production of adrenal hormones, and prevents the gland from becoming bigger. Thus the adrenal problem is solved.
Some of these will actually get smaller while on Lupron! It is the carcinomas that may continue to enlarge and continue to over secrete the hormones (i.e. the "non responders") that are the problem. These need to be removed surgically when possible. My recommendations for treatment are still surgery as the first choice for healthy ferrets. Lupron as my second choice and for those that are at high risk for surgery/anesthesia. Melatonin is my third choice.
Unfortunately too many people and vets still think that Lupron just regrows the hair while the tumor continues to get worse, and the ferret ends up dying a horrible death. This is just not the case! Unfortunately some of the carcinomas do not respond as well to Lupron, and some of them will continue to grow and continue to over secrete the sex hormones. Then surgery becomes the best option, even though it is a higher risk surgery.
That is why I use the monthly version of Lupron, so I can check the adrenal glands and the response monthly. Not responding or gland(s) getting bigger, then time for surgery before they become inoperable.