INTRODUCTION

Spaying females or neutering males is a very common procedure for dogs and cats. For a long time, it was recommended almost automatically, but now we know it’s not always the best option for every animal.

In this article, based on the latest updates from WSAVA (World Small Animal Veterinary Association), I explain clearly the main benefits, the health risks that may increase after sterilization—especially joint issues and behavior changes—and how to make an informed decision with your vet.

BENEFITS OF STERILIZATION

Sterilization is still, in many cases, the best tool to reduce abandonment and prevent serious diseases. Key benefits include:

✅ Prevention of pyometra A life-threatening uterine infection in adult female dogs and cats. Removing the ovaries and uterus eliminates this risk.

✅ Lower risk of mammary tumors If the female is sterilized before her first heat, the risk drops significantly. This protection decreases with age.

✅ Prevention of ovarian, uterine, and testicular tumors Removing reproductive organs eliminates the chance of tumors in these areas.

✅ Reduced prostate problems in males Neutering lowers inflammation and enlargement of the prostate (benign prostatic hyperplasia).

✅ Improved behavior In males, it can reduce urine marking, escaping to find females in heat, and some testosterone-related aggression.

✅ Prevention of unwanted litters Animal overpopulation remains a major welfare issue.

POSSIBLE DISADVANTAGES AND RISKS

Despite many benefits, there are side effects to consider:

❗ JOINT AND ORTHOPEDIC DISEASES Sterilization increases the risk of joint problems, especially in large dogs sterilized before skeletal maturity.

Main conditions:

• Hip dysplasia More frequent and severe in dogs sterilized young. In Golden Retrievers and Labradors sterilized before 6 months, risk is 2–5 times higher than in intact dogs.

• Cranial cruciate ligament rupture Up to 2–3 times more common in some breeds. Hormonal changes may affect joint tissues. Weight gain after sterilization worsens the risk.

• Elbow dysplasia Risk increases.

• Intervertebral disc disease Higher risk in small breeds like Dachshunds sterilized before 12 months.

• Delayed growth plate closure May cause bone deformities or fractures. Documented in Rottweilers.

❗ TUMORS WITH HIGHER INCIDENCE Some tumors decrease, but others increase—especially with early sterilization:

• Osteosarcoma (bone cancer): More common in sterilized large breeds.

• Hemangiosarcoma: Higher risk in some breeds.

• Lymphoma and mast cell tumors: Some studies show links.

❗ OBESITY AND METABOLIC ISSUES After sterilization, metabolism slows down. Without changes in diet and exercise, many animals gain weight. This can lead to joint and heart problems and increase the risk of diabetes.

❗ URINARY INCONTINENCE Especially in young sterilized females of medium and large breeds, urine leakage may occur at rest.

❗ BEHAVIOR CHANGES (NOT ALWAYS POSITIVE) This is often overlooked. Many believe sterilization always improves behavior, but it’s more complex.

Possible changes:

• Fear and anxiety: Some animals become more insecure after hormone removal.

• Noise phobias: Like fireworks or storms.

• Fear-based aggression: Not dominant aggression, but a reaction to insecurity.

WHEN IS THE BEST TIME TO STERILIZE?

There’s no one-size-fits-all answer. It depends on several factors:

🔹 Breed/size and age Large and giant breeds have higher risks of joint issues and bone tumors if sterilized too young. It’s better to wait until growth plates close:

• Females: 12–18 months

• Males: 12–24 months

In small/medium breeds, early sterilization is still acceptable. For cats, it’s recommended to control population and disease transmission.

In my experience, if not strictly necessary, it’s better to wait until at least 2 years old—especially in animals with joint issues. This also supports physical and emotional maturity.

🔹 Lifestyle and management If the animal goes outside without control, preventing unwanted litters may be a priority—especially in cats.

🔹 General health and genetics If the dog has a family history of joint problems, discuss it carefully with your vet.

🔹 Temperament If the dog or cat shows fear, insecurity, or aggression, it’s important to consult a behavior specialist before deciding.

CONCLUSION