Female cats will undergo their first estrous, or heat cycle, when they become sexually mature. This can occur as early as four months, but the typical age is somewhere between six and nine months of age. Estrus is the period when a female is receptive to mating with a male, shows signs of being in heat, and can become pregnant during this time. If the female does not become pregnant, she will continue through the estrous cycle and will go into heat every few weeks until she either becomes pregnant or is spayed.
Cats in heat will exhibit signs that can be quite annoying for owners. If they are spayed, those signs should not be present. However, there are a few conditions where spayed cats will continue to show signs of being in heat. Here, we will discuss the signs of heat in cats, causes of heat signs in a spayed cat, and why treatment is important if your cat is in heat after a spay.
Signs of Heat in Cats
Unlike dogs, the female cat in heat does not have a vaginal discharge. Her signs are typically behavioral in nature. The more common signs an owner may notice is that she becomes unusually affectionate and quite vocal. She may urinate or spray in the house in an attempt to let local tomcats know she is receptive to mating. She also has a tendency to stick her rear in the air and wiggle her back end when she is petted. If a cat that has been spayed is exhibiting signs of being in heat, this could be an indication there is still sex hormone in her system. If you notice any signs of heat in your spayed cat, please speak with your veterinarian.
Causes of Heat Signs in Spayed Cats
Ovarian Remnant Syndrome
If a spayed cat shows signs of heat, it is possible that there is ovarian tissue still in the body and producing estrogen. This can happen for a few different reasons. In rare cases, a small piece of ovarian tissue could be left behind during surgery, allowing continued secretion of estrogen and signs of heat. In other cases, a female cat could possess accessory ovarian tissue separate from the main ovaries that could continue to secrete estrogen after a spay is performed In even more rare cases, if a small amount of ovarian tissue accidentally fell back into the abdomen during the spay surgery, it could continue to secrete estrogen if it could develop a new blood supply. Owners may not notice a change in their cat's behavior right away and signs of heat may not develop until months after surgery.
A cat showing signs of heat after a spay should go the vet as soon as possible for testing. This often includes bloodwork to determine if hormone levels are high and consistent with active ovarian tissue. Occasionally imaging such as an ultrasound will be performed to look for the remaining reproductive tissue but it is usually quite small. Once it has been determined that a pet has an ovarian remnant, surgery should be performed to locate and remove it. This will stop unwanted heat behaviors as well as to prevent increased risk of disease related to ongoing exposure to estrogen, including mammary cancer and stump pyometras.
After a cat is spayed, a small stump of uterine tissue remains inside the abdomen where the tract is tied off. As long as there are no female hormones available, the stump will be a small, inactive tissue. However, if hormones are circulating due to an ovarian remnant or other source of estrogen, this tissue will be active. Over time, an infection of the uterine tissue can develop, which is known as a pyometra. When a pyometra develops in the stump, vaginal discharge may be observed, and the cat may have other signs of illness including fever, lethargy, or decreased appetite, If a stump pyometra is suspected, exploratory surgery may be necessary to remove it as well as to locate the ovarian remnant that supplied the hormones. Your veterinarian will help determine the right treatment plan for your cat.
Adrenal tumors can also produce hormones. The adrenal glands are 2 small glands located next to the kidneys that normally produce important hormones for many body functions. However, tumors of the adrenal glands can produce hormones in excess that can cause a number of different symptoms. In very rare cases, these tumors could produce excessive sex hormones and lead to behavior changes consistent with being in heat. In this situation, signs of heat are constant, they don't cycle as with ovarian tissue. A number of tests may be performed to determine if this is the cause of your cat's symptoms including blood work and abdominal ultrasound to look for a tumor. Exploratory surgery is necessary to visualize the tumor as well as to remove it with the affected adrenal gland. This can be a very complicated surgery.
Topical estrogen-containing creams for humans may be accidentally ingested by cats or other pets. When these creams are applied to the user's hands or arms, they are easily accessible to an affectionate cat who may lick them off. A female cat exposed to these creams can potentially manifest signs of heat but will not show a predictable hormone cycle. She might also show other signs of estrogen exposure including mammary development, swollen vulva, pale gums, or hair loss. The best way to avoid this is for owners to use gloves during application and to make sure to wash hands and to keep cats and other pets away from any part of the body where this cream is applied.
Your Cat was not Spayed
In some cases, a cat showing signs of heat may turn out to be intact, meaning she was never spayed in the first place. This is most common in cases of an adult cat being adopted or a stray cat who is found as an adult without a clear history of spay or previous heat cycles. Sometimes owners believe the cat was spayed based on a lack of heat cycles at the time of rescue, or perhaps they are told by a previous caretaker that the cat is believed to be spayed. In any case, your veterinarian can check for a spay scar by shaving your cat's belly, and if there is any doubt, blood work can be done to check your cat's hormone levels. Nowadays, many animal shelters and rescue groups also apply a small green or blue tattoo mark on the abdomen after a spay to ensure a cat's spay status can be easily confirmed.
Why is Treatment Important?
Hormones have important roles in the body, however they can also have harmful effects. Long term exposure to female sex hormones can dramatically increase the risk of mammary cancer. This is why it is recommended to spay cats prior to their first heat cycle. So speak with your veterinarian right away if you notice your spayed cat is experiencing signs of heat. They will work with you to determine what is causing the behavior change and identify the best way to treat them.
Barnette, Catherine. Ovarian Remnant Syndrome In Cats. VCA Animal Hospitals, 2020.
Pyometra. American College of Veterinary Surgeons, 2020.
Daniel, Gideon et al. Clinical Findings, Diagnostics And Outcome In 33 Cats With Adrenal Neoplasia (2002–2013). Journal Of Feline Medicine And Surgery, vol 18, no. 2, 2015, pp. 77-84. SAGE Publications, doi:10.1177/1098612x15572035