Countering the Effects of Neuter


If your dog has already been neutered, there are some things you can do to help him live the healthiest and happiest life possible. The key to keeping your dog healthy is to assess and confirm the point in time that his adrenal glands are no longer able to compensate for the loss of his testes and the sex hormones they produce.

For many dogs, after they are neutered, they appear to be okay, i.e., no major health problems, no behavioral issues.  If they live in a happy environment with adequate attention and exercise (we will discuss the significance of these in more detail later), they may reach 7 or 8 years of age before you notice any problems.  If that’s the case, thank your lucky stars. Your dog was neutered after his bony growth plates had closed. The bony plates generally close between 4 and 18 months of age, depending on the individual dog. If this is the case for your dog, he probably won’t be afflicted with the worst of the orthopedic problems we have detailed on this website. However, no neutered dog is immune to the hormonal chaos neuter creates – the difference is the timing.

There are a significant number of male dogs who experience behavioral changes after neuter, and for some the changes are dramatic and immediate. At this point in time, most veterinarians are recommending obedience training and/or behavior modification and if these are not satisfactory, they might prescribe antidepressant medications. From our perspective, this approach is counterproductive or at best, merely ineffective. To correct a problem you must first accurately identify the underlying cause of the problem. The negative changes in your dog’s behavior are the product of structural and functional changes in their brain due to a lack of sex hormones. The preferred remedy is to balance their hormones and hopefully achieve the hormone levels of an intact dog (please see our section entitled “The Stress Response System” for a detailed explanation of this phenomenon and discussion of remedies). Balancing hormones offers the best opportunity to enhance physical health as well as restore the balance of neurochemicals  (i.e. serotonin, norepinephrine, dopamine, etc.) in the brain. Balancing hormones is complicated and when behavior is still problematic after hormone balancing (or if hormone balancing is not available), we favor supplementation with SAMe (full details provided later on this page) and perhaps DHEA rather than antidepressants. Antidepressants have significant side effects and are not designed to address excess norepinephrine and the other aforementioned neurochemical imbalances generally found in the brain of symptomatic, neutered dogs.

If your dog does not experience orthopedic problems, the first warning signs the adrenal gland cannot compensate may be general lethargy and perhaps some confusion.55 Don’t assume it’s inevitable because he is getting older. Many neutered dogs as they age exhibit the behavioral characteristics of early Alzheimer’s patients which would include confusion, mood disorders, aggression, and depression (often interpreted as lethargy). For dogs affected in this manner, DHEA supplementation may be highly beneficial-see our Stress Response System page for a more complete explanation. The first step is to have your dog’s thyroid gland hormones and adrenal/sex hormones (i.e., estrogen, testosterone, progesterone and DHEA) tested for imbalance. If the thyroid gland hormones are low, most veterinarians should be very comfortable prescribing thyroid hormone supplements. However, if any of the adrenal and/or sex hormones are low, it may not be in your dog’s best interest to supplement the thyroid hormone alone. In case studies where adrenal/sex hormones are also abnormal, adrenal/sex hormone replacement therapy returned the thyroid levels to normal without the need for thyroid hormone replacement.105

The aforementioned research is important for two reasons:

  1. It exemplifies the complexities of the thyroadrenal interactions.
  2. It proves the point that recovery from the endocrine disruption of neutering is not straightforward; endocrine (hormonal) interactions within your dog are a complex web of inter-related feedback mechanisms.

Hormone Replacement/Balancing

As in the example above, simply adding in a hormone which is low may not solve the problem, but actually make it worse. On the other hand, your dog’s behavior problem(s) may be a barometer as to the necessity for testosterone replacement. And, replacement of testosterone may resolve the observed behavior problem(s).

Another significant reason for hormone replacement is to counter the more systemic damage done to your dog’s endocrine system by neutering. HAHD_hormone_imbalanceWith respect to hormone replacement therapy, we find hormone “re-balancing” may be the better term to use. Some hormones may be in excess, while others may be deficient. Identifying the hormone levels, and supplementing/reducing their corresponding quantities to physiologically ideal ranges, is difficult, but necessary. The Endocrine Society’s latest Scientific Statement on the subject of endocrine disruption explains:

“…levels of any hormone must be within a physiologically relevant range to be most effective. Excursions outside of that range to superphysiological (elevated) or subphysiological (depressed) levels for any extended period nearly always result in dysfunction or disease.” 176

This common sense concept explains why you need to balance hormones to the levels of a normal, intact dog. Further, the veterinary community’s policy of setting alternate normal ranges of hormones for neutered dogs illustrates their complete failure to respect or understand endocrine and metabolic function. For specific instructions regarding testing your dog’s hormone levels, please visit our FAQ page. If testing reveals a need for additional testosterone, please visit our Testosterone Supplementation page.

Restoring hormonal balance can help prevent the development of cancer, Cushings, diabetes, and other endocrine related diseases. Please refer to the Diseases Overview page and “The Stress Response System” page on this website for a more in-depth explanation of the overarching effects of spay/neuter on your dog’s ability to respond to stress. Additionally, immunonutrition therapy is emerging as an effective adjunct to hormone balancing in dogs. Immunonutrition therapy is a discipline wherein the goal is to enhance immune system activity by including specific nutrients in the diet. Please refer to our Cancer page for more details on Billy’s experience with immunonutrition therapy.

If your dog was neutered before his growth plates closed, the first health related problems you see may be orthopedic, and they may occur at a young age. If your dog struggles to sit and get up from a sitting position and is moving poorly in general (see Billy’s videos on his timeline), your dog may have torn the cranial cruciate ligament in his knee(s). If just one knee’s ligament is torn, the orthopedic surgeon most likely will not insist the other knee’s ligament will tear. However, based upon our current knowledge as to the cause, it’s pretty clear you can expect the second knee to have the identical problem. Similarly, in the case of elbow and hip dysplasia, you can expect the dysplasia to be bilateral.

If you proceed with surgery for any of the aforementioned orthopedic issues, you should test your dog’s thyroid, sex and adrenal hormones after it appears he has fully recovered from the surgery (this will vary for every dog). You want to be sure you have allowed adequate time for the adrenal gland to recover from the stress of surgery before testing. You will be the best judge as to whether your dog has recovered to the level of strength and activity that he possessed prior to the injury. This is a pivotal point because outward appearance would indicate your dog has healed from his surgery. However, the initial damage neuter inflicted upon your dog’s brain and endocrine system likely will not allow normal immune or metabolic response to the stress of a subsequent surgery. The stress of a surgery may stimulate your dog’s adrenal glands to produce cortisol, so much cortisol that the adrenal gland is no longer able to produce the normal level of sex hormones your dog requires. Lack of sex hormones will again cause functional and structural changes in your dog’s brain as well as dysregulation of the endocrine system. This will predispose your dog to metabolic disease (e.g. diabetes) as well as immune-mediated disease (e.g. cancer). The thyroid may be a problem as well, but it may resolve after hormone re-balancing as described above.

In males, it is practically impossible to address their hormone imbalance without a hormone panel. There are simple blood tests to determine levels of estradiol, testosterone, thyroid, progesterone, and DHEA. We do want people to get tangible evidence of hormonal imbalance before making significant changes through supplementation. It is quite likely your dog will be deficient in testosterone and no veterinarian would give your male dog testosterone supplements unless there is a documented deficiency. Our internal medicine specialist was unwilling to give Billy testosterone even though we documented a complete absence of testosterone. Our primary care veterinarian was kind enough to help us, but it was not without reservations. He feared Billy would become aggressive after receiving testosterone.

It is difficult to explain why the veterinary community continues to treat testosterone as a hormone only important to reproduction, and beyond that function, a hormone that creates only problems for the male dog. As explained earlier on this page, the Endocrine Society – the largest global membership organization representing professionals (medical doctors, scientists, researchers, and educators) from the field of endocrinology has concluded persistently low or high levels of any hormone nearly always results in dysfunction or disease. It is no exaggeration to say that in modern medicine and endocrinology testosterone is not considered a marginal hormone, or a lifestyle hormone for those men seeking eternal youth. Research has shown its deficiency leads to a serious deterioration of the health of men. This deterioration is rooted in the metabolic syndrome and its sequelae: diabetes mellitus type 2, atherosclerotic disease, osteoporosis and sarcopenia.  All of these conditions strongly limit physical independence in old age and accelerate morbidity and mortality.128

It is this fundamental misconception on the part of the veterinary community (that sex hormones are only relevant to reproduction) which initially allowed spay/neuter to be institutionalized as the preferred means of canine population control. Spay/neuter persists today because veterinary professionals continue to ignore the mounting research that recognizes the breadth of the influence sex hormones have over entire body systems independent of reproduction.

To further confirm the veterinary community’s misconceptions about testosterone, we found that testosterone did not make Billy more aggressive. In fact, testosterone had the opposite effect – it made Billy much less fearful. Once you understand the workings of the endocrine system in response to stress (please see the “The Stress Response System” page on this website), and how the brain is damaged by neuter, it is logical that for dogs who suffer from leash aggression, or fear aggression (see the Behavioral Effects of Neuter), testosterone supplementation can make them less aggressive.

Male dogs may also be deficient in progesterone. For male dogs who exhibit signs of agitation (sometimes to the point of panic), generalized anxiety and/or fear of new people, dogs or new situations, they might very well be deficient in testosterone as well as progesterone. We know that progesterone has a strong effect on the serotonin, norepinephrine, dopamine and endorphine receptor sites in the brain, which are involved in mood regulation. If testing reveals a deficiency of DHEA, estradiol and/or progesterone, you should be able to supplement under the supervision of your veterinarian.

Another option may be a supplement humans often take, SAMe, for mood regulation.  There is evidence that SAMe behaves similarly in dogs’ brains, and may mimic the activity of progesterone in the dog brain. The research best supports the concept that SAMe helps neutralize norepinephrine in the brain. Norepinephrine is found in excess in the brains of dogs unable to appropriately respond to stress. An alternate theory is that SAMe acts by helping to increase the availability of neurotransmitters, such as serotonin and dopamine (which are attributed to feelings of emotional well-being), as well as increasing the number of neurotransmitter receptors. There are SAMe supplements available that have been formulated specifically for dogs. A general dosage guideline is 10mg. of SAMe per pound daily, although some manufacturers provide tablets dosed for a range of body weights. Scientific research also supports SAMe’s ability to promote liver health and joint comfort – key components to physical health and wellbeing. SAMe works best when given in the AM on an empty stomach at least 1 hour before a meal. Research has reported SAMe’s side effects to be negligible.

Sometimes when a dog has elevated liver enzymes, a combination of SAMe and silybin (milk thistle) 17 is recommended. These are available as generics formulated for dogs or in combination as Denamarin. Denamarin does not require a prescription and was recommended for Billy by our vet. Denamarin was beneficial to his liver, somewhat helpful for his joints, and extremely helpful for his fear and anxiety. If your dog has a deficiency in testosterone as well as progesterone, SAMe supplements or even injections of progesterone might help, but their activity could be overshadowed by the absence of testosterone.

Males may also have too much estradiol, also termed “hyperestrinism“. Estradiol is the most powerful form of estrogen and is generally predominant in females, not males. If the estradiol is excessive, but moderately so, currently the veterinary “experts” who provide the hormone panels and treatment recommendations to your veterinarian will recommend supplementation with a moderate aromatase inhibitor (e.g., melatonin and/or lignans like flaxseed). However, in our opinion, this is not a prudent recommendation.  We would refer you to our page on Hormones and the Endocrine System under the Diseases section so that you might see the unintended consequences of melatonin supplementation.

If there is a gross excess of estradiol, as Billy experienced, you will have to ask your veterinarian to prescribe a strong aromatase inhibitor to block the production of estradiol. At our specific request, our internal medicine specialist prescribed a very strong aromatase inhibitor, i.e., anastrozole, for Billy. Anastrozole has been tested extensively in dogs (with the intent of evaluating its safety for humans) and is regarded as safe to use in canines.

Earlier on this page, we mentioned the importance of adequate attention and exercise for your dog, especially if he is neutered. There is scientific evidence to support these “common sense” suggestions. There are neurochemicals found in the brains of dogs and humans which promote feelings of happiness or bliss. In light of all the negative effects of neuter on the brain, an activity that enhances brain chemistry may make a significant difference in your dog’s quality of life.

As is the case with humans who run frequently, researchers have discovered that dogs also experience a “runner’s high”.  The “high” comes from the release of endocannabinoids (eCBs) during moderate to high intensity exercise. Walking, such as on a leash, is not sufficient intensity of exercise to stimulate release of eCBs.166 Our dog Billy was run close to 6 miles daily at the beach near our home, and we found it was extremely helpful in alleviating his anxiety. Not everyone can run far enough or fast enough to give their dog adequate exercise to provoke the release of eCBs. But certainly most anyone can play fetch with their dog. Some dog guardians comment that their dog  seems obsessed with their ball/frisbee. Perhaps their dog is simply addicted to the “high” running after the ball/frisbee provides them.

We also suggest it is important to give your dog adequate attention. Certain neurochemicals known to provide psychological benefits are generated in humans when they have positive interactions with other species. Consistent with the “Canine-Human Connection“, a study was conducted in 2003 to see if the same neurochemicals and psychological benefits would be present in dogs. The study’s results confirmed that concentrations of beta-endorphin, oxytocin, prolactin, beta-phenylethylamine and dopamine increased in both humans and dogs through their positive interaction.167 In 2010, at the 12th International Conference of Human-Animal Interactions, scientists presented their findings confirming that friendly human-dog interaction releases oxytocin in both humans and dogs.


The most concrete recommendation we can offer is with respect to vaccinations. Because spay/neuter has an adverse effect on the immune system, guardians of spayed/neutered dogs must be cautious with respect to vaccinations. A study was conducted in 200534 to analyze adverse events diagnosed within three days of vaccine administration in dogs. The vaccine associated adverse events included nonspecific vaccine reaction, and allergic reactions varying in severity from a rash or hives all the way to anaphylaxis (which can block breathing and be fatal). The study found danger of an adverse reaction goes up substantially when a dog is spayed or neutered, and the less a dog weighs, the more likely they are to experience an adverse reaction. Further, the risk increases substantially with each additional vaccination given at one time.

Therefore, best practice would be just one vaccination on any given day, with a reasonable period of time between vaccinations. This precautionary approach becomes even more important when your dog is small.

Additionally, in 2017 the American Animal Hospital Association (AAHA) canine vaccination task force updated their vaccination guidelines. Rabies vaccinations remain effective for a period of 1 to 3 years, depending upon your previous method of vaccination. In 2011 the task force changed the previous recommendation for distemper, parvovirus and adenovirus vaccination from once a year to a frequency of once every 3 years. The task force also acknowledged in the 2011 guidelines that immunity lasts at least 5 years for distemper and parvovirus, and at least 7 years for adenovirus. In 2017 there are no notable changes to these core vaccine recommendations (rabies, distemper, parvovirus and adenovirus), except that the parainfluenza virus is now considered an optional core vaccine according to the AAHA. In these 2017 vaccination guidelines, for the first time, the AAHA acknowledges that titer tests are useful in determining dogs’ immunity to distemper, parvovirus, and adenovirus. A titer test is a blood test designed to evaluate immunity, so if the titer test shows immunity to one of these core vaccines, you can safely avoid additional vaccination.

The problem we had was in researching the process of titering we could not find any solid guidelines. It seemed that the effectiveness of the process of titering required a vet experienced in the process of interpretation to get it right. Not everyone has access to a vet with this skill set. We did, however, find a simple solution to this problem as provided in an article by Dr. Karen Becker (her interview with Dr. Valente about spay/neuter is on this website). Dr. Becker states:

“I prefer to run IFA (immunofluorescence antibody) titer tests for parvo and distemper because they give a clear-cut answer, either ‘yes the animal is protected,’ or ‘no the animal is not protected.’ Because most veterinary schools are still not adequately educating their students about titer test interpretation, this removes any question of whether the pet is protected or not.”

The 2017 updated vaccination guidelines also discuss a group of new vaccinations which are non-core (strictly optional). These would include bordetella (kennel cough), leptospira, Borrelia burgdorferi (Lyme), canine influenza viruses H3N8 and H3N2 and Crotalus atrox (western diamond rattlesnake). Common sense would dictate a pet guardian only consider these immunizations if they believe their dog’s environment provides substantial risk of exposure to one of these pathogens, and their dog is healthy.

We are not advocating the avoidance of vaccinations. We see this as an opportunity for shared decision making63 with your veterinarian to provide your dog with vaccinations on a schedule that is best for your dog. An article by Dr. Karen Becker regarding these new 2017 vaccination guidelines may give you some information to consider when discussing your dog’s vaccination schedule with your vet. For example, when Billy was an uncontrolled diabetic and had hormone imbalance we were trying to address, our primary care vet agreed with our decision to avoid the core vaccines.