Are there any advantages of seeing a neuroendocrinologist over an endocrinologist or neurologist, and how is their training different?

Depends upon sympt: If you suffer vision loss secondary to pituitary gland problems, hopefully this has been addressed medically or surgically, but you will need hormonal maintenance, and most endocrinologists can handle this well. Some of these docs focus in subspecialty areas, such as diabetes, and you can sort this out by inquiring from your internist as to the best fit for you. Local medical society can help.

Depends on problem: A neuroendocrinologist would be a neurologist taking one or two years of fellowship training in endocrinology or an endocrinologist taking one or two years of training in neurology. Typically that type of specialist would be found in your larger academic or teaching hospitals. I don't know which specialist would benefit you most unless you tell me the exact problem you are having.