Seven types of steroids
Are there different kinds of steroids?
Steroids are one of the most commonly prescribed medications for dogs. When we say steroids, we are usually referring to prednisone, but there are actually seven classes of steroid drugs. Each one works differently on the body, and each has its own potential side effects. It is important to understand what type of medication you are giving your dog and to recognize the signs of potential problems the drug may cause.
In many cases, problems can be prevented by using the lowest dose possible for the shortest period of time. Dogs should be closely monitored while they are on any type of steroid medication. If your veterinarian is recommending steroid treatment for your dog, be sure to discuss the pros and cons of the medication before giving it. Many of these drugs are not recommended for dogs in a breeding program, especially during the time they may be pregnant.
Glucocorticoids are the steroids most often prescribed by veterinarians for our dogs. The list of glucocorticoid drugs is long and includes familiar drugs such as prednisone, prednisolone, triamcinolone, betamethasone, dexamethasone, flumethasone, fludrocortisone, hydrocortisone and methylprednisolone. When given at low doses, glucocorticoids reduce inflammation. At higher doses, these steroids will suppress the immune system. Glucocorticoids are prescribed to treat allergies, immune-mediated diseases and shock. They may also be given as part of the therapeutic protocol for some types of cancer and are used in the treatment of the adrenal condition known as Addison’s disease.
Glucocorticoids are administered in several ways. They can be given by injection, orally as pills or liquid, topically as creams, ointments or sprays, or by inhalation with an inhaler or nebulizer. The short-term use of glucocorticoids is generally safe, but when they have to be administered at especially high doses over extended periods of time, or cannot be tapered to at least every other day, there is a risk of serious side effects. These side effects include an increase in thirst and hunger, susceptibility to infections, ulcers of the stomach or intestines, muscular weakness and abnormal behaviors.
A particularly serious side effect is the development of Cushing’s disease, which is a condition, also known as hyperadrenocorticism, where the adrenal glands produce an excess of certain hormones, especially cortisol, commonly known as cortisone. Cushing’s disease may develop from a tumor of the adrenal or pituitary gland. Iatrogenic Cushing’s disease occurs when there is excessive cortisol in the system from the prolonged use of oral or injectable glucocorticoids. This type of Cushing’s disease can be reversed when the dog is weaned off the glucocorticoids.
Mineralocorticoids are responsible for maintaining the balance of water and electrolytes within the body while glucocorticoids play a role in the stress response. When dogs have Addison’s disease, their adrenal glands do not produce enough of either of these two types of steroids – mineralocorticoids and glucocorticoids. Treatment for Addison’s disease involves daily doses of a glucocorticoid, usually prednisone, and monthly injections of a mineralocorticoid, desoxycorticosterone (Percortin-V, Zycortal).
Fludrocortisone (Florinef) is a synthetic hormone dispensed in tablet form for oral administration. It has both mineralocorticoid and glucocorticoid action. All these drugs are safe but can cause increased thirst and urination. More serious side effects are generally seen only when dogs are dosed incorrectly or abruptly stop receiving their medications.
Adrenal cortical steroids are a type of steroid used more for diagnosing disease rather than treatment. Adrenocorticotropic hormone, also known as ACTH or corticotropin, and cosyntropin are used to diagnose dogs with Cushing’s disease and Addison’s disease. These drugs are given by injection as part of an ACTH stimulation test to determine whether or not a dog’s adrenal glands are functioning normally.
ACTH stimulation tests are also used to monitor dogs with Cushing’s disease that are being treated with the drug mitotane, since this drug can have a narrow margin of safety in some dogs. Side effects are unlikely with adrenal cortical steroids since they are not given long term.
Anabolic steroids like stanozolol, boldenone and nandrolone are less commonly used in veterinary medicine. Since anabolic steroids promote muscle growth, they are administered in select cases in which serious muscle deterioration has developed as a complication of a primary disease.
Anabolic steroids are synthetic derivatives of testosterone. They promote increased appetite, weight gain and improved mental attitude, so they are given to reverse debilitation associated with surgery, trauma, illness and aging. In order to get the best results when using anabolic steroids, the dog must be fed adequate amounts of protein and calories, as well as given proper treatment for the underlying disease.
Anabolic steroids should never be given to dogs that will be used for breeding because they are known to cause serious birth defects. This type of steroid has androgenic (male hormone) effects, such as increased libido in males and abnormal sexual behavior in females. Other negative effects on the reproductive system include low sperm count, failure to have estrus cycles, shrinking of the testes and enlargement of the clitoris. Anabolic steroids can induce early closure of the growth plates, thereby retarding growth.
The main indication for use of anabolic steroids is the treatment of debilitated animals; however, they are often misused to gain a competitive advantage in performance animals. Approved veterinary formulations are no longer marketed in North America. Currently, any anabolic product for veterinary use (aside from bovine ear implants) can be obtained only from a compounding pharmacy.
Estrogen is a steroid hormone produced mainly from the ovaries, but can also originate from the adrenal glands and placenta, which is the tissue that communicates between the fetuses and mother during pregnancy. Estrogen has many functions. It is involved in the release of eggs from the ovaries and prepares the vaginal tract for breeding by thickening and lubricating the lining of the vagina. It assists with the motility of the egg and sperm toward each other and the transport of the embryo toward the uterus at the correct time.
Estrogen also assists with preparation of the reproductive tract for delivery of the fully developed fetus. It is involved in the development of the mammary tissue through puberty. Estrogen also affects a bitch’s behavior, making her more attractive and receptive to male dogs.
Estradiol is a naturally occurring estrogen. Diethylstilbestrol (DES) and estriol (Incurin) are the more commonly used synthetic versions of estrogen. These steroid hormones are used to treat urinary incontinence in spayed female dogs. Estrogens may also be given to female dogs to encourage them to come into heat or to intact male dogs to treat benign prostatic hypertrophy.
When giving supplemental estrogen, dosages must be closely monitored, as estrogens can have serious side effects. These include bone-marrow suppression that leads to blood disorders; pyometra, which is a potentially fatal infection of the uterus; feminization of male dogs, and an increased likelihood of some types of cancer.
Progestins are steroid hormones that are prescribed to postpone heat cycles or alleviate false pregnancies in female dogs and treat benign prostatic hypertrophy in male dogs. They may also be used for some types of skin problems or to modify aggressive behavior.
Megestrol acetate (Ovaban) and medroxyprogesterone are the most commonly used progestins in dogs. Potential side effects include increased appetite and thirst, behavioral changes and mammary-gland enlargement. More serious side effects include the potential for developing diabetes mellitus, acromegaly (a hormonal disease that causes enlargement of the head), Cushing’s disease, pyometra, reproductive disorders and some types of cancer.
Androgens are a class of steroid hormones that includes testosterone, milbolerone and danazol. Androgens have a wide variety of uses, such as treating hormone-responsive urinary incontinence in male dogs, suppression of heat cycles and alleviation of false pregnancies in female dogs, and as part of the therapy for some types of immune-mediated blood disorders.
Mibolerone (Cheque Drops) was a commonly used product for postponing estrus cycles in bitches. This product is no longer readily available. Masculinization of female dogs, liver toxicity and the promotion of some types of cancer are the most concerning side effects.