We hope everyone had a wonderful holiday season this year and that their family, friends and pets all made it through happy, healthy, and with lots of yummy food stuffed into their bellies. For this post I thought I’d write about something we are seeing more and more in dogs that come to the clinic — Cushing’s syndrome. Cushing’s syndrome is used to describe the signs in dogs where the hormone cortisol is continuously secreted in doses far beyond what is necessary. Cortisol is a hormone that is produced in response to stress (like when you realize it’s Christmas eve and you still haven’t gotten anything for your Nana) to enhance blood sugar, fat, carbohydrate and protein metabolism. The organ responsible for controlling cortisol secretion is the pituitary gland in the brain, which controls the secretion of a variety of different hormones.
It is important to note that there are two types of Cushing’s — Cushing’s syndrome (adrenal Cushings), which is caused by a tumor called an adenoma growing on the adrenal gland forcing the oversecretion of ACTH, and Cushing’s disease (pituitary Cushings). The mechanism in which Cushing’s disease develops is when an adenoma starts growing on the pituitary gland and stimulates the oversecretion of ACTH (adrenocorticotropic hormone), which controls the secretion of cortisol via the route of the adrenal glands. The difference between these two is that with Cushing’s syndrome, the production of ACTH (and subsequently cortisol) from the tumor on the adrenal gland in Cushing’s syndrome is self-limiting in that the body will naturally send feedback to stop producing ACTH. Cushing’s disease on the other hand does not have a negative feedback mechanism to cap ACTH and cortisol production.
Over time, this overproduction of ACTH and cortisol causes a number of symptoms to appear, including but not limited to weight gain (they tend to have “coffee table backs”), increased dilation of capillaries, loose/weak skin, hair loss, muscle weakness, bone loss, sore joints and brittle hair. Increased levels of cortisol can also cause insomnia, hypertension, an increase in urine output (polyuria), water drinking (polydipsia), and can even lead to insulin resistance and subsequently diabetes.
So what can you do if you suspect your dog has Cushing’s? Specific tests designed to test for Cushing’s exist, and can be done at any vet clinic (lab work may need to be sent out, however). These tests can test for things such as urinary cortisol to creatinine ratios, dexamethasone suppression tests and ACTH stimulation tests. Once confirmed, your dog will need to go be put on a dose-dependent medication (specifically, Trilostane) that will control cortisol production and keep it at a normal range. To determine the right dose of medication, the aforementioned tests must be done periodically to monitor your dogs appropriate dose because it can change over time. Unfortunately, as surgical intervention to remove these tumors is rarely successful, if your dog has Cushing’s they will most likely need to be taking this daily dose of medication for the rest of their life.
Remember, any concern you may have for your pet’s health, no matter how menial you think it may be is always worth finding out an answer to. Call and book an appointment to speak to your vet if you think your dog might have Cushing’s or you are looking to better control your dog’s current Cushing’s treatment.