Hormones are regulatory biochemicals produced by "endocrine" glands and expected to circulate through the body to their target organs. They are effectively messengers telling different organs what to do, when to do it, and how hard to work at what they are doing. There are hormones naturally produced in the body; however, most therapeutic hormones are modified versions of their natural counterparts, designed to maximize the effects that a doctor might want maximized. Different hormones have tremendous therapeutic benefit. Here are some examples.
Dexamethasone is a member of the glucocorticoid class of hormones. This means they are steroids but, unlike the anabolic steroids that we hear about in sports, these are catabolic steroids. Instead of building the body up, they are designed to break down stored resources (fats, sugars and proteins) so that they may be used as fuels in times of stress.
Diethylstilbestrol (DES) has only one primary use: treating sphincter tone incontinence in female dogs. DES is used at extremely low doses to avoid the toxicity issues that have been a problem for estrogen derivative medications.
There is really only one use for this medication: the treatment of hypoadrenocorticism (Addison's disease). In this disease, the adrenal gland is unable to produce hormones called mineralocorticoids. In the normal animal, these hormones are responsible for the balance of sodium and potassium and without these hormones a life-threatening circulatory shock ultimately results. Fludrocortisone acetate prevents this circulatory crisis.
Prednisone and prednisolone are members of the glucocorticoid class of hormones. They break down stored resources (fats, sugars and proteins) so that they may be used as fuels in times of stress. We do not use the glucocorticoids for their influences on glucose and protein metabolism; we use them because they are the most broad anti-inflammatory medications that we have.