강아지 호르몬 반응성 종양(프로게스테론) 증상과 원인, 진단·치료와 관리 포인트 총정리

If Your Dog’s Mammary Lumps Are Hormone-Related — Causes and Treatment of Progesterone Tumors

Oncology/CancerDiseasesMeongsiljang Veterinary Advisory Board

Hormone-responsive tumors in dogs, such as those influenced by progesterone, are growths stimulated by sex hormones and primarily occur in female dogs. Early diagnosis and appropriate treatment are crucial.

What Are Hormone-Responsive Tumors (Progesterone) in Dogs?

An illustration highlighting the reproductive organs and hormonal pathways in dogs.

In dogs, progesterone stimulates the proliferating ductal epithelial cells of the mammary glands, increasing the secretion of growth hormone (GH). The effects of progesterone are most pronounced during periods of high hormone levels, such as the diestrus phase after estrus or when progestin medications are administered. The increased growth hormone can lead to conditions like acromegaly, insulin resistance, and diabetes, making early detection of changes crucial. - Progesterone Dependence: Higher progesterone levels promote the proliferation of mammary ductal epithelium and the secretion of growth hormone. - Primary Site of Occurrence: Excess growth hormone originates from the proliferating ductal epithelium of the mammary glands, not the pituitary gland. - Importance of Early Detection: Since symptoms may not be obvious in the early stages, regular check-ups are essential for identifying changes promptly.

What Are the Main Causes of Hormone-Responsive Tumors?

The primary driver of progesterone-related changes in dogs is prolonged elevation of progesterone levels. During the luteal phase following estrus, progesterone remains high for about one to two months, a period during which proliferation of the mammary ductal epithelium can occur alongside increased growth hormone secretion. Similar changes may also arise with the administration of progestin-based medications. - Hormonal excess: Prolonged elevation of progesterone after estrus stimulates proliferation of the mammary ductal epithelium and promotes growth hormone secretion. - Progestin medications: Exogenous administration of progestins can induce growth hormone excess in a manner similar to endogenous progesterone. - Ovariohysterectomy status: Removing the ovaries eliminates the source of endogenous progesterone, helping to reduce changes driven by luteal-phase progesterone.

A graph showing rising progesterone levels during a dog’s heat cycle

Check for Key Symptoms and Signs

In dogs, excess growth hormone caused by progesterone can lead to the following changes. However, some dogs may show no obvious symptoms, so please consult your veterinarian if you have any concerns.

Physical changes: Excess growth hormone (acromegaly) may cause thickening of tissues in the face and paws, or widening of the spaces between teeth.

Increased drinking and urination: If insulin resistance or diabetes develops, your dog may drink more water and produce more urine.

Changes in appetite and weight: Food intake and body weight may differ from usual.

Reduced energy: Your dog may become less active and tire more easily.

General decline in condition: You may notice changes in behavior or vitality compared to normal.

Because these signs can overlap with other conditions, an accurate diagnosis is essential.

Emergency Signs Requiring Immediate Veterinary Visit

If your pet experiences a sudden drop in energy, rapid breathing, complete loss of appetite, or shock-like symptoms such as fainting or difficulty breathing, seek veterinary care immediately. Worsening of underlying hormonal disorders, such as diabetes, can be life-threatening.

Diagnostic Tests for Accurate Diagnosis

To evaluate progesterone-related hormonal abnormalities in dogs, we use a combination of tests. - Imaging: Ultrasound is an excellent screening tool, and if needed, CT or MRI can help determine the location and structure of the lesion. However, imaging alone cannot determine whether the tissue is overproducing hormones. - Blood tests: We check progesterone levels and look for any accompanying changes, such as insulin resistance or diabetes. - Hormonal function tests: These complement imaging by assessing whether the lesion is overproducing hormones (functional status). - Tissue biopsy: If necessary, we take a tissue sample to confirm the nature of the lesion, and the veterinarian will integrate all results to develop the best treatment plan.

An ultrasound image showing an enlarged uterus

Treatment Methods and Step-by-Step Approach

Treatment is determined by the underlying cause and the dog’s overall health status. If endogenous progesterone is the cause, ovariohysterectomy to remove the source of progesterone is the definitive approach. After surgery, the stimulation of growth hormone by progesterone decreases. If progestin administration is the cause, discontinuing the medication is helpful. Concurrent conditions such as diabetes may require separate management, and the veterinarian will develop a treatment plan tailored to the patient’s condition.

A veterinarian performing an ovariohysterectomy on a dog

Home Care and Follow-Up Procedures

After surgery, your pet needs plenty of rest and attentive care to recover properly. - Surgical site care: Keep the area clean and prevent your pet from scratching or straining it. - Medication administration: Ensure your pet takes pain relievers or antibiotics exactly as prescribed. - Activity restriction: Limit exercise to short walks for 1–2 weeks, and prevent running or jumping. - Follow-up appointment: Schedule a check-up with your veterinarian within 1–2 weeks post-surgery to monitor healing progress. - Regular health screenings: To help prevent future hormone-related conditions, we recommend routine check-ups every 6 months to 1 year.

Breed-Specific Precautions and Recurrence Prevention

Changes in growth hormone levels due to progesterone are closely linked to states of high progesterone, such as the diestrus phase after estrus or the administration of progestin medications. Some reports have noted progesterone-related diabetes during diestrus and pregnancy in Swedish Elkhounds. In intact females, this condition can recur with each diestrus cycle, so consulting with a veterinarian about spaying (ovariohysterectomy) to eliminate the source of progesterone may be beneficial.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Are hormone-responsive tumors cancerous?

In dogs, the effects of progesterone primarily manifest as proliferation of the mammary ductal epithelium and excess growth hormone (GH), which is generally distinct from cancer (malignant tumors). However, if any changes are suspected, an accurate evaluation by a veterinarian is necessary.

Will medication alone be sufficient?

If the cause is a progestin medication, discontinuing it can be helpful. When endogenous progesterone is the culprit, removing the source through an ovariohysterectomy is the definitive treatment, and any concurrent conditions such as diabetes may require separate management.

Can it come back after surgery?

Removing the ovaries eliminates the source of progesterone produced during the luteal phase, significantly reducing the likelihood of progesterone-related changes recurring. However, similar changes may still occur if progestin medications are administered again.

Which breeds are at higher risk?

Rather than a specific breed, elevated progesterone levels—such as those seen during the luteal phase after estrus or with progestin administration—are more significant factors. Some reports have noted progesterone-related diabetes during the luteal phase and pregnancy in Swedish Elkhounds.

How can we prevent it?

Along with regular check-ups, you may consider discussing with your veterinarian the option of an ovariohysterectomy (spaying) to remove the source of progesterone when necessary. Avoiding unnecessary use of progestin medications can also be helpful.

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References

[1] Liptak, J.M. and L.J. Forrest. 2013. 21 – soft tissue sarcomas. In Withrow and MacEwen’s Small Animal Clinical Oncology, 5th edition. R.L. Page, S.J. Withrow, and D.M. Vail, editors. St. Louis: W.B. Saunders.

[2] Preziosi, R. et al. 1995. Histological grading of canine mammary tumors: a prognostic factor. Veterinary Pathology, 32(3), 245–252.

[3] Bray, J.P., R.S. Doyle, and C.A. Burton. 2009. Minimally invasive inguinal approach to the treatment of perianal gland tumors in dogs. Veterinary Surgery, 38(4), 385–392.