Difference between revisions of "Hyperoestrogenism - Dog"

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Hyperoestrogenism is caused by excessive levels of oestrogen in the body and has different aetiologies depending on the sex of the animal.

In the bitch it is usually associated with cystic ovaries or more rarely a functional ovarian tumour. These are mostly granulosa-theca cell in origin and 10-20% are malignant. It can also occur iatrogenically through the administration of oestrogens used to treat mismating and urinary incontinence.

In the male dog the syndrome is associated with a Sertoli cell tumour of the testicles or a male feminising syndrome for which the cause in unknown.

Hyperoestrogenism also occurs in the female ferret if an entire jill remains unbred for an extended period of time.

Hyperoestrogenism is very rare in cats.

Clinical signs


Bilaterally symmetrical alopecia and hyperpigmentation of the perianal, perigenial and axillary areas, enlargement of the nipples and vulva, comedones and pyoderma, oestrus cycle abnormalities such as nymphomania and pyometra.

Male dogs

Bilaterally symmetrical alopecia and hyperpigmentation, gynaecomastia, pendulous prepuce, testicular mass, prostatomegaly, attractiveness to other male dogs and loss of libido.


Bilaterally symmetrical alopecia around the ventrum and tail, weight loss, pale mucous membranes, enlarged vulva and a serous or mucopurulent vaginal discharge.



In all cases, history and clinical signs are suggestive.

Haematology and biochemistry of is usually unremarkable except where oestrogen-induced bone marrow suppression occurs, in which case a non-regenerative anaemia, thrombocytopenia and leucopenia are seen.

Other endocrine disorders which can cause the same skin changes should be ruled out, such as hypothyroidism and hyperadrenocorticism.

Blood oestrogens may be elevated in some dogs, however false positive and false negative results are common.

Definitive diagnosis for bitches is by exploratory laparotomy to investigate the ovaries.

In male dogs a mass may be palpated in the testicle.


History and clinical signs along with a PCV of less than 20% and depression of all blood lines is highly suggestive.



Therapy for any concurrent infections together with supportive care if oestrogen-induced myelosuppression is present (fluids and whole blood transfusion).

Ovariohysterectomy is the treatment of choice if an ovarian cyst or tumour is present. Radiographs of the thorax are useful prior to surgery to check for any metastases in the case of neoplasia. Most dogs show an improvement in clinical signs within 3-6 months.

Male dogs

Bilateral castration is the treatment of choice for testicular tumours. Supportive care such as fluids or whole blood should be considered if bone marrow suppression is present. Any concurrent infections of the skin or prostate gland should be assessed. Most dogs show and improvement in clinical signs within 3-6 months.


Ovariohysterectomy is the fastest way to remove the source of oestrogens, although intitial treatment is dictated by the PCV. A blood transfusion might have to be performed first.

In milder cases, hormone treatments such as proligestone can be used to induce ovulation. Signs of oestrus will abate within 10-11 days but it might take up to 4 months for the anaemia to resolve.

The prognosis depends on the length of time the jill has been in oestrus and the PCV on presentation. If it is above 25% the prognosis is good. If it is below 15% the outlook is poor and intensive treatment along with multiple blood transfusions will be necessary for several months.

Female ferrets should not remain in heat longer than a month and ovulation should be induced by mating or hormone therapy before this. Ovariohysterectomy at 6-8 months of age is recommended for jills that are not to be bred.


Hubrecht, R. (2010) The UFAW Handbook on the Care and Management of Laboratory and other Research Animals, John Wiley and Sons

Paterson, S. (2008) Manual of skin diseases of the dog and cat, John Wiley and Sons