Introduction
Spaying or neutering your dog is a common decision for pet owners—but did you know it could have long-term health effects beyond reproduction? New research funded by the AKC Canine Health Foundation (CHF) reveals how removing reproductive hormones may influence your dog’s risk for certain diseases, including cancer.
This breakthrough focuses on the role of luteinizing hormone (LH), which becomes abnormally elevated after spay/neuter surgery. Scientists are now uncovering how this hormone may affect various organs and even contribute to serious conditions like urinary incontinence, hypothyroidism, and lymphoma. (See “An Update on the Health Effects of Spay/Neuter in Dogs” for more information on these grants and their outcomes.)
Key Points
- Dogs spayed or neutered can have LH levels up to 30 times higher than normal.
- Elevated LH may affect the thyroid, urinary tract, immune system, and even cancer development.
- Spayed females with urinary incontinence have more LH receptors in the lower urinary tract.
- Gonadectomized dogs show more LH receptor-positive lymphocytes, which may promote lymphoma.
- Research is ongoing to develop strategies to manage or prevent these hormone-related effects.
Challenge Background
For decades, spaying and neutering have been promoted as responsible pet ownership practices. While these procedures prevent unwanted litters and reduce certain health risks, they also eliminate the gonads, the source of reproductive hormones like estrogen and testosterone.
These hormones do more than regulate reproduction. They influence bone growth, behavior, immune function, and even cancer resistance. Once removed, the body loses its natural hormonal feedback loop, causing LH to rise dramatically. Until recently, the long-term effects of this hormonal imbalance were poorly understood.
The Breakthrough
Researchers at Oregon State University, led by Dr. Michelle Kutzler, are investigating how elevated LH levels after gonadectomy may contribute to disease. Their studies show that LH receptors are found in many non-reproductive tissues, including:
- Urinary tract: Spayed females with incontinence have more LH receptors here. Hormone therapy that lowers LH can improve symptoms.
- Thyroid gland: LH receptors near thyroid-stimulating hormone (TSH) receptors may interfere with thyroid function, contributing to hypothyroidism.
- Immune system: Gonadectomized dogs have more LH receptor-positive lymphocytes. These cells are also found in cancerous lymph nodes, suggesting a link to lymphoma.
With funding from CHF Grant 02751-A, Dr. Kutzler is studying how LH receptor activation may cause cancerous lymphocytes to migrate and spread, potentially accelerating the progression of lymphoma.
Impact & Next Steps
This research could lead to new ways to prevent or manage hormone-related diseases in dogs. Veterinarians may one day use hormone-modulating therapies to reduce LH levels or block its effects in high-risk dogs.
The findings also support a more personalized approach to spay/neuter decisions, taking into account a dog’s breed, sex, and age. Future studies will continue to explore how LH interacts with different tissues and how to mitigate its adverse effects.
For now, dog owners and veterinarians can use this information to make more informed decisions about reproductive surgery and long-term health planning. Learn more about CHF’s diverse portfolio of canine health research grants at akcchf.org/research.
References:
1. Kutzler, M. A. (2020). Possible Relationship between Long-Term Adverse Health Effects of Gonad-Removing Surgical Sterilization and Luteinizing Hormone in Dogs. Animals: An Open Access Journal from MDPI, 10(4).
https://doi.org/10.3390/ani10040599
