Hyperoestrogenism - Dog

Introduction

Hyperoestrogenism is caused by the excess production 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 she remains unbred for an extended period of time.

Clinical signs

Female

Females

Ovarian Imbalance Type 1 Seen in adult bitches who present with alopecia and increased pigmentation round the perianal, perigenital and axillary areas. Caused by:

• Cystic ovaries.
• Ovarian neoplasia.

Males

Dogs present with bilaterally symmetric alopecia, similar hyperpigmentation to that seen with female dogs with ovarian imbalance, loss of libido and gynaecomastia. The dogs become attractive to other male dogs. Caused by:

• Sertoli cell tumour.
• Male feminising syndrome.