Overproduction of Estrogen in Dogs

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PetMD Editorial

Published Jul. 1, 2008

Hyperestrogenism in Dogs

Estrogen -- a type of hormone -- is naturally produced in female dogs. It is responsible for normal sexual behavior and development, and the customary biological function of the female reproductive tract. Overproduction of estrogen can result in what is known as estrogen toxicity (hyperestrogenism). This can happen without any outside interference or it can occur when estrogens are being introduced artificially.

Estrogens sometimes cause abnormal (cystic) cells to line the uterus and this permits the invasion of bacteria from the vagina. The cervix is open during "heat," but if it is closed it can lead to a serious infection (pyometra). In addition, a concentration of estrogen can result in infertility, as well as an imbalance in the blood.

Symptoms and Types

Weakness (lethargy)
Pale gums
Bleeding—skin, urine, stool, vomit
Fever
Persistent infections
Thinning of the hair
Female characteristics in males
Infertility
Prolonged estrus
Enlarged vulva
Enlarged teats in female
Decreased attraction to opposite sex
Excess attraction to opposite sex in females (nymphomania)
Bleeding from the vulva
Hair loss (alopecia)
Tumor on tail in male (stud dog tail)
Testicular mass in male
Testicular atrophy

Causes

Excessive production of estrogen
Administration of estrogen supplements
Ovarian cysts
Ovarian tumor
Testicular tumor

Diagnosis

Complete blood count (CBC)
Bone marrow biopsy (aspirate)
X-ray of the abdomen
Ultrasound of the abdomen
Thorough examination of testicles in intact males
Needle biopsy (aspiration) of testicular masses
Ultrasound-guided aspiration of ovarian cysts
Biopsy of lymph nodes
Skin biopsy to determine cause of hair loss

Treatment

Stop estrogen supplementation
Supportive care, including antibiotics and blood transfusions
Blood transfusions, if anemic
Antibiotics in case of infections
Masses may be examined via small scope instrument (laparoscopy)
Masses may be removed via incision (laparotomy)
If estrogen is not being administered artificially, surgical neutering in either male or female
Removal of testicle or ovary may be considered for valuable breeding animals
Testicular prosthetic devices are not advised
Medications to increase blood production in bone marrow
Medication to induce ovulation may be prescribed if there are cysts

Living and Management

Recovery may take a while -- up to several months -- so be prepared to provide long-term care for your pet. Be vigilant in providing prescribed medications and aware of any changes in your pet. Blood tests (and sometimes bone-marrow biopsies) must be performed to evaluate your pet's response to the therapy.

Do not give estrogen-containing compounds unless advised to by your veterinarian. Females will undergo tests to determine whether ovulation is occurring.

In addition, a male dog should not show signs of feminization once a testicular tumor has been removed.