Hyperestrogenism in Dogs – Vet Guide 2025 🐶⚕️🩺

By Dr. Duncan Houston BVSc

I’m Dr Duncan Houston, BVSc, founder of Ask A Vet. Hyperestrogenism—also called estrogen toxicity—occurs when estrogen levels in dogs become abnormally high. Causes include ovarian or testicular cysts or tumors, or exposure to estrogen-containing medications applied to humans. Potentially life-threatening, hyperestrogenism can affect hormone function, skin health, blood production, and fertility. In this comprehensive 2025 guide, we'll cover causes, symptoms, diagnostics, treatment options, and post-care strategies to support your dog’s full recovery. 🩺✨

📘 What Is Hyperestrogenism?

Hyperestrogenism is a condition where estrogen levels exceed normal ranges, causing systemic effects. Estrogen is produced by ovaries, testes, adrenal glands—and may also be absorbed indirectly from topical human treatments.

🧬 Causes & Risk Factors

• Ovarian origin: follicular cysts or estrogen-producing ovarian tumors, often in older intact females, but may also affect younger dogs with cysts.
• Testicular origin: Sertoli cell tumors (especially in cryptorchid dogs), Leydig/interstitial cell tumors; ~25% create estrogen symptoms.
• Exogenous exposure: hormone replacement creams/patches from owners, particularly toy breeds, are especially susceptible.
• Rare sources: adrenal tumors or estrogen-mimicking mycotoxins in contaminated feed (e.g., zearalenone).

🚩 Clinical Signs

In Female Dogs

• Prolonged heat cycles, vulvar swelling/discharge (bleeding even if spayed).
• Enlarged teats or mammary gland changes, alopecia (non-pruritic), hyperpigmentation.
• Hormonal imbalance can cause infertility, uterine infection (pyometra) or cystic endometrial hyperplasia.
• Weakness, fever, pale gums, bruising due to bone marrow suppression—may lead to bleeding or infection.

In Male Dogs

• Testicular masses, atrophy, prostate enlargement or dysfunction, blood in urine, and infertility.
• Gynecomastia (male mammary enlargement), pendulous prepuce, symmetrical alopecia, hyperpigmentation, “stud-dog tail”.
• Bone marrow suppression leading to anemia, thrombocytopenia, immunosuppression, and bleeding/bruising.

🔍 Diagnostic Work-Up

1. Clinical history & exam: intact vs spayed/neutered status, exposure to hormones, and behavioral/physical changes.
2. Blood tests: CBC showing cytopenias, chemistry, and hormonal assays (estrogen, testosterone).
3. Bone marrow evaluation: aspirate/biopsy if bone marrow suppression is suspected.
4. Imaging: abdominal ultrasound or radiographs to identify ovarian/testicular/adrenal lesions and feed contamination signs.
5. Tissue sampling: fine-needle aspirate or biopsy of ovarian/testicular mass or cyst; cytology of skin if alopecia is present.
6. Exclude exogenous sources: assess owner medication history and exposure spots.

💊 Treatment & Management

1. Remove the Estrogen Source

• Surgery: Ovariohysterectomy (spay) for females; castration for males. Removal of masses/cysts is often curative.
• Targeted removal: Single-ovary or testicle removal may be considered in breeding animals.
• Stop external exposure: Discontinue owner hormone therapy or change application site.

2. Supportive & Symptomatic Care

• Antibiotics to treat or prevent infections from bone marrow suppression.
• Blood transfusions as needed for anemia or bleeding issues.
• Bone marrow stimulants—EPO analogs if severe anemia.
• Pyometra or cystic endometrium treatment—surgical removal, fluid therapy.

3. Long-Term Monitoring & Prognosis

• Expected recovery time ranges from weeks to few months, depending on severity.
• Skin lesions and hormonal abnormalities typically resolve with source removal.
• Bone marrow function usually normalizes, but may take several weeks.
• Follow-up includes CBC monitoring, hormone levels, and ultrasound as needed.

🏠 Home Care Recommendations

• Strict medication compliance and wound care after surgery.
• Owner hygiene—avoid direct contact with hormone application sites.
• Supportive environment with easy access to food, water, and rest areas.
• Monitor for signs of bleeding, infection, or behavioral change.
• Maintain regular vet check-ups to confirm recovery progress.

✨ Key Takeaways

• Hyperestrogenism results from excessive estrogen, causes include cysts, tumors, or external exposure.
• Both males and females can develop skin changes, reproductive irregularities, and bone marrow suppression.
• Diagnosis relies on blood tests, imaging, biopsy, and exposure history.
• Surgical removal of the estrogen source is primary and often curative.
• Supportive care addresses anemia, infection, and systemic effects.
• With early intervention and proper follow-up, most dogs recover with minimal long-term effects.

🐾 Ask A Vet

• Consult about surgery or hormone source removal via Ask A Vet.

If you notice symptoms like persistent bleeding, hormonal dysfunction, bald patches, or anemia—especially in intact dogs—don’t wait. Contact your veterinarian or reach out to Ask A Vet. Early diagnosis and management offer the best chance for a happy, healthy recovery. 🩺