Dogs, Diet and Disease: Cushing's Pt 1-4
From "Dogs, Diet, and Disease": Cushings Part 1
Since cortisol affects nearly every cell in the body, an excess of cortisol results in a wide variety of symptoms. This variety of symptoms is known as a syndrome. Consequently, some veterinarians refer to this situation as Cushings syndrome or more specifically canine Cushings syndrome.
Whichever term is used, the underlying problem remains the same. Too much cortisol or cortisone (a synthetic steroid) is circulating through the dogs body. In most cases, excess cortisol production stems from a malfunction of the pituitary gland, at the base of the brain. In some cases, it may stem from a problem of the adrenal glands, located near the kidneys. In other cases, Cushings disease is induced by the use of prescription steroids.
Cortisols primary job is to ensure the presence of glucose in the bloodstream. It does this by balancing the effects of insulin during carbohydrate metabolism. Whereas insulin helps mobilize glucose into hungry cells and out of the bloodstream, cortisol does almost the opposite. Cortisol helps mobilize glucose back into the bloodstream by breaking down muscle and adipose (fat) tissue.
When excess cortisol is present, though, it breaks down far too much muscle tissue (catabolism), causing muscle weakness and wasting. This can affect the dogs skeletal muscles with signs of fatigue, lethargy, or reduced coordination. Cortisol can also weaken other muscles, such as the heart, causing cardiacirregularities, murmurs, and congestive heart failure. It can weaken the bladder wall and sphincter muscles, causing urinary incontinence and dribbling. It can affect dental health by weakening ligaments in the gums.
When the body breaks down adipose tissue (lipolysis) it raises levels of cholesterol and tryglicerides circulating in the bloodstream. Catabolism and lipolysis are the same processes that occur during periods of starvation. Believing this to be the case, the appetite center of the brain erroneously tells the dog to eat more. So, despite the fact that Cushinoid dogs have sufficient levels of circulating glucose and ravenous appetites, they still feel hungry. This is known as polyphagia (excess hunger).
Catabolism can also cause dramatic rises in blood glucose levels, particularly in stressful situations. Dogs that are simultaneously diabetic may require higher levels of insulin to handle the rise in glucose. This scenario is sometimes referred to as insulin resistance, but it may also be described as simply a greater need for insulin. Excess cortisol can cause a once-regulated diabetic to become uncontrolled and can cause dog owners much frustration.
Cushinoid dogs are more susceptible to infection since excess cortisol depresses the immune system. This includes both the production and function of white blood cells. Pathogens reproduce more freely and attack the body. Skin, ear, and urinary tract infections are commonly seen in these dogs.
Cortisol normally regulates kidney function. Excess adrenal gland activity may result in the retention of sodium (and a rise in blood pressure). Cortisol increases the filtration rate, causing excessive urination (polyuria), and excessive drinking (polydipsia). Polyuria, in turn, causes excessive excretion of magnesium, a mineral crucial to normal body function and metabolism. Without magnesium, calcium can not be deposited into skeletal bone. Instead, high levels of calcium remain circulating in the bloodstream.
Cushinoid dogs commonly experience heat intolerance. These dogs pant excessively and seek cool surfaces to dissipate their body heat. This problem can stem from two factors. First, excess cortisol raises metabolic rate and body temperature in an attempt to kill perceived invaders. Second, a scenario is created in which magnesium levels are deficient and cortisol levels are in excess. This results in potassium being moved out of the cells, into the bloodstream, and excreted by urination. (Magnesium normally maintains potassium inside the cells and sodium in the fluid around the cells.) Potassium loss results in symptoms of fatigue and heat exhaustion.
From "Dogs, Diet and Disease": Cushings Part 2
Calcium and phosphorus levels are normally maintained at a 2:1 ratio in the body. When levels of serum phosphorus are high, the body tries to maintain the normal ratio by raising levels of serum calcium. To achieve this, the body increases parathyroid gland activity (hyperparathyroidism), and secretes hyperparathyroid hormone. This activity pulls calcium from the intestinal tract, or from skeletal bones and cartilage (known as demineralization). This scenario may contribute to joint and bone pain (limping) and collapsed tracheal cartilage.
In these cases, calcium may also be deposited into the bodys soft tissues. Such areas include the skin (resulting in itchy sores known as calcinosis cutis), the lungs, bladder (calcium stones), skeletal joints (resulting in signs of arthritis) and, some experts believe, the corneal and lens tissues of the eye.
Cortisol is normally involved in the maintenance of the bodys soft connective tissues. Excess cortisol disrupts the structure of elastic tissue under the skin and mucous membranes. This results in thinning of the hair and skin, cracked noses, and a loose, pendulous appearance to the dogs abdomen.
Chronic excesses of cortisol cause lesions to develop on the liver. Such liver disease can raise levels of circulating liver enzymes.
Cortisol is involved in the normal function of the nervous system. Excess cortisol and insufficient magnesium levels negatively affect cognitive function, resulting in a condition sometimes described as canine cognitive disorder. Signs can include mood changes such as depression, aggression, stupor, hearing impairment, and confusion (circling).
Cushinoid dogs are more susceptible to epileptic seizures. Opinions are split as to the reason behind this. Some experts believe that excess cortisol and insufficient magnesium lower the tolerance level toward seizure activity. Others believe that pituitary tumors place pressure on areas of the brain and initiate seizure activity.
Related to nervous system function is that of ophthalmic function. Cushioned dogs (and sub-clinical Cushioned dogs) sometimes experience dry eye syndrome, uveitis, or sudden blindness. (See Chapter 12, Additional Health Concerns for more details on these conditions.)
Under normal conditions, cortisol levels follow a seasonal and circadian rhythm (a 24-hour pattern) in humans and most other mammals. Levels are normally highest during the daytime and lowest at night. Cortisol has an inverse relationship to another hormone called melatonin. Melatonin is produced by the pineal gland, deep within the brain, and is considered to be responsible for the waking and sleeping patterns of a normal circadian rhythm.
Melatonin levels are normally lowest during the daylight and highest as darkness falls. As levels increase, so does drowsiness. In some cases of hyperadrenocorticism, excess cortisol seems to disrupt this cycle. Many dogs may sleep during the day and experience varying degrees of insomnia during the night. Some dogs are simply agitated. Others retire, only to wake their owners repeatedly during the night. Insufficient levels of magnesium also contributeto increased irritability and insomnia.
From "Dogs, Diet and Disease": Cushings Part 3
From DDD, (but not a complete list/ discussion of diagnosis techniques***8230;too long to reprint here):
Diagnosing Cushings Disease
A variety of diagnostic tests are available to confirm cases of HAC and differentiate their causes. Your veterinarian may chose one particular test or proce-dure over another to determine the most appropriate therapy and accurate prognosis for your dog.
These tests are not, however, 100***37; accurate. Numerous factors can contribute to the interpretation of the test results. Since the immune system responds to a vast number of stressors with the release of cortisol, the tests can easily be skewed by psychological stress, chronic illness (diabetes, inflammatory bowel syndrome, etc.), steroid use, or exhaustion of the glands, themselves.
The best veterinarians look at the entire picture when diagnosing Cushings disease and problems of excess cortisol production. This includes physical signs and findings, the owners observations, and blood cell counts, in addition to Cushings tests. Many dogs exhibit clinical signs of excess cortisol without ever truly testing positive for Cushings disease. Tests are commonly repeated when results are questionable.
ACTH Stimulation Test
This test is considered by many veterinarians to be the best initial test for diagnosing the presence of hyperadrenocorticism. It is relatively simple, quick, and cost-effective. It operates on the theory that when a normal dog is given ACTH by injection, the adrenal glands will be stimulated to produce cortisol.
Low Dose Dexamethasone Suppression (LDDS) Test
The LDDS test is helpful as a second opinion when a veterinarian finds results of the ACTH stimulation test questionable. The LDDS test also helps differentiate between cases of pituitary-dependent disease and adrenal-dependent disease.
High Dose Dexamethasone Suppression (HDDS) Test
The HDDS test is more helpful in differentiating cases of pituitary-dependent and adrenal-dependent HAC. High doses of dexamethasone can suppress ACTH/cortisol production in most pituitary-dependant dogs. As with the low-dose test, this procedure involves intravenous injection of dexamethasone, and anin-hospital stay of eight hours. If the post-injection level of cortisol is less than 50% of the pre-injection level, PDH is suspected.
The Urinary Cortisol Creatinine Ratio Test (UCCR)
This test measures cortisol levels in the urine. It is used as an indication of Cushings disease and usually requires substantiation by a more specific Cushings test.
From "Dogs, Diet and Disease": Cushings Part 4 Diet/Treatment
Diet is a valuable and important part of treatment, since IMHO, the diet contributes to the problem in the first place, even though a lot of allopathic folks with think it nonsense. However, it's not rocket science to think that the cells and hormones are affected by the raw materials we put into a body***8230;
I'm only going to include some brief portions of the classic drugs used to treat Cushings. The diet sections are so long***8230;I just can't cut and paste all of that. At this point I think you'all realize that I'm a big proponant of a biologically appropriate diet***8230;or as close as you can get.
The drug Lysodren (also known as Mitotane or o,p-DDD) is a powerful medication that was originally developed as a chemotherapy drug but is also useful in cases of HAC. It destroys the cortisol-producing layer of the adrenal gland. It can be used both in cases of adrenal-dependent and pituitary-dependent HAC
Anipryl (also known as L-Deprenyl, Eldepryl, or Selegiline) is a medication humans use to control Parkinsons disease. It is used in dogs to control signs of canine cognitive dysfunction (senility) and more recently, to control pituitary-dependent HAC in some countries. It is ineffective in cases of adrenal-dependent disease. Anipryl is considered to be less toxic than Lysodren, and some veterinarians consider it a good choice for uncomplicated cases of Cushings disease diagnosed early on.
This is an antifungal medication that, through a side effect, reduces levels of cortisol. It does this by inhibiting enzyme reactions that normally result in the release of adrenal cortisol. It must be administered every 12 hours and can be expensive. It is prescribed less commonly than either of the previously mentioned drugs. As with Lysodren, Ketaconazole requires a loading phase and periodic ACTH tests to check effectiveness.
Some holistic veterinarians also prescribe the oral supplement Phosphatidyl Serine (PS) in cases of excess cortisol production. PS is a natural phospholipid that is normally made by the body through a series of complex processes. Levels deteriorate with age and stress. PS improves nervous system and memory function in humans. Studies also indicate that PS raises circulating levels of such hormones as dopamine and melatonin, and reduces levels of ACTH and coritsol.
Phosphatidyl Serine was originally tested on dogs prior to FDA approval for use in humans. Adverse effects were not noted in these dogs after prolonged use on high doses. The average dose for human use is 300 mg per day. The owners of small dogs (weighing 10 to 25 pounds) have reported reduced symptoms of cortisol with 50 mg to 100 mg per day. The owners of medium sized dogs (weighing 40 to 50 pounds) have reported good results with 200 mg per day. Reduced symptoms are often noted in 2 to 3 weeks.
Dietary therapy (including the addition of PS) may be especially helpful in the following two situations:
1) in the absence of a formal Cushings diagnosis, and
2) when a dog is poorly controlled with traditional Cushings medications.
While PS is available at most health food stores and does not require a doctors prescription, it is still wise to keep your veterinarian apprised of your plans.
There is also a med available in the UK called Trilostan that some folks are importing for use on their dogs here in the States. It is unproven, but currently undergoing clinical trials in Scotland, I believe. Dog owners are having good anecdotal success with it according to posts on the CanineCushing's-autoimmune list.
Written by Caroline
Very interesting info Moonstr8. While I haven't experienced Cushings in my dogs, I do have a horse with Cushings. I thought the two were different diseases in each but based on your info there are many similarities.
Do you know if Pergolide or Chastetreeberry have ever been used in treating Cushings in dogs?
Agree with you that diet is as much a part of treatment as medication.
Thanks again for posting this information. I hope I won't ever have to deal with this in my dogs, but if Cushings is as prevalent in dogs as it is becoming in horses this is important information to have on hand.