Estrogen Toxicity in Cats

Estrogen Toxicity in Cats

Estrogen toxicity is a condition in which a group of estrogen compounds (female hormones), either produced in excess within the body or administered from the outside, become poisonous to the body. Estrogen toxicity is seen most commonly in reproductive-age females and aged males.

Estrogen toxicity can occur due to estrogen-producing tumors or from the administration of estrogen type medications. These medications are often used to treat a multitude of disorders. Examples include diseases of the prostate, anal tumors, and urinary incontinence (inability to control urination).

What to Watch For

  • Lethargy
  • Pale gums (from anemia)
  • Bleeding associated with the skin, urine, stool, or vomit
  • Fever
  • Persistent or recurrent infections
  • Thin hair coat
  • Feminization (female sex characteristics) in males


    A variety of tests may be necessary to diagnose estrogen toxicity and determine the severity. Recommended tests may include:

  • Complete blood count (CBC) to reveal a decreased red cell and platelet count, and a normal or increased white blood cell count. Later in the disease, the white cells are decreased as well.
  • Bone marrow aspirate and cytology to confirm decreased cell content
  • Radiographs/ultrasound of the abdomen to reveal tumors capable of producing estrogen
  • Thorough examination of the testicles in intact (un-neutered) males.


  • Remove source of estrogen
  • Provide supportive care
  • Give blood transfusion in the severely anemic animals
  • Administer antibiotics in the individuals with infections secondary to low white blood counts

    Home Care and Prevention

    Administer all prescribed medication by your veterinarian. Watch your pet closely for any change in his/her condition. Recovery may take anywhere from several weeks to several months.

    Do not administer estrogen containing compounds to your pet unless instructed by your veterinarian and monitored very closely.

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