Dear Lisa,
Welcome to you and Pepper, and WOW you've done a great job of keeping your girl healthy and happy up to age 17! First off, even though folks here do give various supplements to support healthy body functioning, there are no nonprescription drugs that will address the root cause of Cushing's and lower cortisol sufficiently to control the disease. So it really will take treatment with either trilostane (or Lysodren, the other Rx option) to control the Cushing's, assuming it truly is the cause of her symptoms. Having said that, at age 17, you may want to consider pluses-and-minuses of Cushing's treatment before rushing in to treat Pepper.
Cushing's is typically a slowly progressive disease but it does have the potential to cause systemic damage over time (from high blood pressure, vulnerability to pancreatitis and infections, high cholesterol, kidney damage, liver inflammation, etc.). So for a younger dog, I'd certainly recommend effective treatment so as to eliminate some of these risks, improve longterm quality of life, and allow the dog to live out his/her normal lifespan. However, for a dog of Pepper's age, immediate quality of life issues seem of paramount importance to me. And there are some trade-offs to treatment, especially for an arthritic dog since the arthritis may actually worsen as the cortisol level drops, necessitating the introduction of additional drugs to better manage the discomfort. Also, especially at the beginning, there can be numerous vet visits and blood draws which can be less than pleasant for a dog who's nervous at the vet (and also hard on the owner's pocketbook
).
I don't tell you any of this to dissuade you from treating if you and your vet agree this is the best path forward for Pepper. But I do think you are the best judge as to how uncomfortable her current symptoms are to you both, and if they are not bothering Pepper all that much -- as I say, you may want to hold off on treating for the time being.
First things first, though -- as Lori says, it'll be great if we can take a look at those test results.
Marianne