Suprelorin Implants for Male Dogs: A Modern Alternative to Castration

Forestside Vets
18 hours ago
3 min read

At Forestside Vets, we’re often asked about alternatives to surgical castration for male dogs. One option that’s becoming increasingly popular is the Suprelorin® implant - a small, reversible hormone implant that temporarily reduces fertility and testosterone. It’s widely used across Europe, especially in some of the Scandinavian countries where reversible options are often preferred.

So what actually is Suprelorin? And how does it compare to traditional surgical castration? Here’s a clear guide to help you decide what’s right for your dog.

What is Suprelorin?

Suprelorin is a tiny implant, placed just under the skin in a quick appointment. It slowly releases deslorelin, a type of hormone known as a GnRH “super-agonist.” Although that sounds counter-intuitive, the science behind it is clever:

Short initial stimulation: For the first couple of weeks, the implant briefly increases signals from the brain to the testes. This can cause a short-lived rise in testosterone.
Then suppression:With continuous exposure, those brain receptors effectively “switch off.” When they stop sending signals, the testes stop producing sperm and testosterone. The result? A dog who behaves physiologically as though he’s been castrated - but without surgery, and only for as long as the implant lasts. Most dogs experience the full effect after 4-6 weeks. The 4.7 mg implant lasts around 6 months; the 9.4 mg implant typically lasts 12 months or more.

What changes should owners expect?

Once testosterone falls, you can expect:

Reduced fertility
Reduction in testicular size
A smaller prostate
Reduced roaming, mounting, and other hormone-driven behaviours in many dogs
A calmer demeanour in some (but not all) individuals

Importantly, because the effect is temporary, fertility returns once the implant wears off.

A note on hormones and health: the LH discussion

You may have seen online discussions about Luteinizing Hormone (LH) and long-term health risks in neutered dogs. Here’s the simple version:

After surgical castration, a dog’s testosterone drops permanently. Without testosterone to “switch off” the brain’s signalling system, LH levels stay high for life.
Some studies are exploring whether these high LH levels could influence the development of certain tumours. The research is ongoing, and we don’t yet have definitive answers.
With Suprelorin, the brain’s signalling system is effectively paused - meaning LH levels stay low during the implant’s active period. This doesn’t automatically make one option “better,” but it’s one of the scientific reasons people are interested in reversible hormone suppression instead of lifelong gonadectomy.

Suprelorin vs Surgical Castration - what’s the difference?

Why some owners prefer Suprelorin

Reversible - ideal if you’re unsure about permanent castration
No anaesthetic - the implant is placed in a normal consultation
Useful as a behavioural trial - a good way to see if lowering testosterone will help before committing to surgery
May avoid some theoretical LH-related risks (research still emerging)

Why some owners still choose surgical castration

Permanent – once it’s done, you don’t need to revisit the decision
Eliminates testicular cancer risk completely
No need for repeat treatment every 6–12 months
Avoids the brief initial testosterone rise seen with the implant
Long history of use with well-understood outcomes

Which option is right for your dog?

There’s no single answer - both approaches have advantages. The best choice depends on:

Your dog’s age, breed, and health
Whether behaviour is a concern
Whether you want a permanent solution
Any worries about anaesthesia or surgical recovery
Whether you’d like to “test drive” the hormonal effect first

Many of our clients find Suprelorin a fantastic stepping-stone: a safe, reversible way to understand how their dog responds to lower testosterone before making a long-term decision.