Calcinosis cutis on dog

Calcinosis cutis caused by long-term corticosteroid exposure. Image courtesy of Dr. Carol Foil

Most people are familiar with cortisone and may even know that it is a steroid but, even though steroids are commonly prescribed to both people and animals, much more knowledge than that is not really mainstream. Steroid hormones are used to treat many types of diseases, and it turns out that by altering the dosage of a steroid, a completely different effect is achieved. This means steroids can treat inflammation, improve appetite, suppress an overactive immune system, reduce secretions, relieve itching, and more. Steroids can be short-acting, long-acting, intermediate-acting, oral, injectable, topical, or even inhalational. With so many uses possible, it is important to know which effect(s) your doctor is going for.

Let's take a few moments to straighten out the vocabulary of steroid hormones to understand what is in that bottle of pills so frequently dispensed. A lot of terminology can be confusing, so it is good to have some basis for what your veterinarian is talking about.

Steroid: A hormone with a cholesterol-based structure is a steroid hormone. There are sex steroids (like anabolic steroids that bodybuilders should probably not be using) and adrenal steroids. The steroids that are most commonly used therapeutically are adrenal steroids.

Corticosteroid: Adrenal steroids can be produced by the center of the adrenal gland or by the outer cortex of the adrenal gland. Corticosteroids come from the outer cortex of the adrenal gland. There are two types: glucocorticoids (which address sugar metabolism) and mineralocorticoids (which address electrolyte metabolism). We are concerned with the glucocorticoids for this discussion.

Examples of Glucocorticoids

Cortisol: This is the natural hormone produced by one's adrenal glands to regulate sugar, fat, and salt metabolism in times of stress.

It turns out cortisol can be made in the laboratory, and when it is, we call it hydrocortisone (or sometimes just plain cortisone.) Hydrocortisone is a common topical steroid used in assorted anti-itch products. Modifications of it make it stronger or longer acting, such as mometasone, which is used in human nasal products as well as veterinary ear medications.

Oral Glucocorticoids

Prednisone: In order for prednisone to become an active hormone, the liver has to convert it into prednisolone. Prednisone can be produced in the laboratory and is readily available as a medication.

Prednisolone: In order for prednisone to become an active hormone, it must be further activated by the liver into prednisolone. Again, prednisolone can be produced in the laboratory and is readily available as a medication.

Methylpredisolone (Medrol^®): By altering the prednisolone molecule in the laboratory, the potential for side effects can be changed. One issue is the increased thirst side effect. By changing the prednisolone structure slightly, less salt retention occurs, leading to less thirst compared to what happens with regular prednisolone. Less thirst means less urination and less chance of an accident in the house.

Dexamethasone (Azium^®): Adding still more methyl groups creates an even stronger steroid with even less salt retention side effects. Dexamethasone can also be manufactured in the laboratory and is readily available as a medication that can be used topically, orally, or as an injectable.

Injectable Steroids

We have already covered dexamethasone, which can be used as an injectable. Other modifications have led to:

Methylprednisolone Acetate (Depomedrol): This steroid is very strong and can maintain an anti-inflammatory effect for several weeks. This is helpful for patients (especially cats) who may not readily accept oral shorter-acting steroids every day. One shot can cover a long period of time, but the downside is that the injection makes for a high dose that wanes over months. The anti-inflammatory effect may last a few weeks, but the suppression of the natural adrenal system continues for months after that.

Triamcinolone (Vetalog): Intermediate-acting but strong, lasting a couple of weeks. Similar downsides as above.

So we have covered some of the benefits of steroid therapy.

That said, side effects from the glucocorticoid group are numerous and can be classified into those seen with short-term and long-term use.

Short-Term Side Effects

A pet on glucocorticoids is likely to experience:

• Increased hunger
• Increased thirst and possibly urinary incontinence for dogs if there is inadequate access to an area for appropriate urination
• Panting (dogs)
• General loss of energy
• Hidden infection being unmasked, especially upper respiratory infections in cats.

These side effects are generally classified as inconvenient but not serious. If a short-acting oral steroid is being used, often simply changing the dosing schedule solves these problems. If a long-acting injectable is used, you simply have to wait for it to wear off.

But there are also more serious side effects:

• Pre-diabetic animals may be tipped over into a diabetic state with steroid use. Often, in these cases, the diabetes resolves once the steroid wears off.
• A similar situation exists for patients with borderline heart function (a situation for which cats are notorious). The extra salt retention from steroid use can prove to be just too much for a heart that can barely manage its normal fluid volume. The salt causes fluid retention, and a borderline heart may not be able to manage.

Even these serious side effects can resolve once the steroid wears off, but it is important to be aware of these possibilities. The above scenarios are rare, but if they happen to your pet, they will not feel rare to you.

Long-Term Side Effects 

Many conditions require long-term suppression of the immune system. Glucocorticoid doses generally include an anti-inflammatory dose that is lower and an immune-suppressive dose that is higher, though with long enough term use, lower doses will become immune-suppressive. When steroid use stretches out for more than four months, a new set of side effects, in addition to those listed above, becomes of concern:

• Latent urinary tract infections in up to 30% of patients. Monitoring for these with periodic urine cultures is necessary. The patient will not have the usual symptoms of urinary infection as the steroid will suppress the inflammation associated with the infection. Culture may be the only way to detect the infection.
• Development of thin skin, blackheads, and poor ability to heal wounds or grow hair
• Development of obesity and muscle weakness
• Hard plaques of diseased skin called calcinosis cutis (see photo above). These plaques are calcium being deposited in the skin.
• Predisposition to infection of any kind/weakening of immune defenses
• Development of Cushing’s syndrome.

All of the above listed effects can be seen and be considered symptoms of this syndrome.

Steroid Alternatives

When a long-term dose of steroids is deemed to be excessive or if the short-term effects become problematic, it is time to seek another medication so as to spare the amount of steroids needed, if not replace the steroid altogether. Recently there has been a proliferation of medication for itch relief without the use of steroids. For alternative immunomodulating drugs, consult your veterinarian.