Hyperoestrogenism of the intact female dog

HYPEROESTROGENISM IN DOGS occurs in three distinctive ways. In the intact female dog, the dermatosis is caused either by cystic ovaries or a functional ovarian tumour (Paterson, 2008; Miller and others, 2013). In the intact male dog, feminisation can occur as a result of a functional tumour of the testicle. The disease can also be iatrogenic as the result of treatment with oestrogen, for example in the treatment of urinary incontinence following ovariohysterectomy (Barsanti and others, 1983). The disorder as seen in the intact female dog is described here.

Clinical features

• Most commonly occurs in middleaged intact female dogs.
• Cases associated with functional ovarian tumours usually occur in older dogs. The most common oestrogen producing tumour is the granulosatheca cell tumour, reportedly 10-20% of which are malignant (Miller and others, 2013).
• Bilaterally symmetrical alopecia beginning in the perineal (Figure 1), inguinal, ventral (Figure 2) and flank regions (Miller and others, 2013).
• Enlargement of the vulva (Figures 1 and 2).
• Enlargement of nipples.
• Comedones on ventral alopecic skin.
• Mammary hypertrophy may occur in some ovarian tumour-induced cases if the tumour secretes progesterone in addition to oestrogen.
• Abnormalities of the oestrus cycle (irregular cycles, prolonged oestrus and associated abnormal sexual behaviour) are possible.
• Secondary seborrhoea.
• Increased risk of pyometra or endometritis.
• Hyperpigmentation of all affected regions (Figures 1 and 2) in chronic cases.

Diagnosis

• History and physical examination is sufficient in uncomplicated cases such as the one illustrated.
• Ultrasonographic examination.
• Exploratory laparoscopy.
• Elevated blood oestrogen levels may support the diagnosis although some dogs have normal blood oestrogen levels owing to increased numbers of cutaneous oestrogen receptors (Miller and others, 2013). Care must be taken with the interpretation of individual oestrogen levels as variability has been reported in normal dogs (Frank and others, 2011).
• Rule-out of other endocrine dermatoses such as hypothyroidism, hyperadrenocorticism, hair cycle arrest and follicular dysplasia may be considered in rare cases without typical signs of hyperoestrogenism.

• Histopathological examination will support the diagnosis of an endocrine disorder, but is not specific for hyperoestrogenism.

Clinical management

• Ovariohysterectomy.
• Chest radiographs are indicated if an ovarian tumour is suspected.
• Full blood count if aplastic anaemia or thrombocytopaenia is suspected on clinical grounds.

Prognosis

• The prognosis is good if no ovarianmalignancy is found.
• Response (reduction of vulval swelling, regrowth of hair) is usually within three months. Occasional cases, particularly those with extensive hyperpigmentation, may take longer to respond – up to six months.
• Cases with aplastic anaemia or thrombocytopenia have a more guarded prognosis.

• Metastasis of an ovarian tumour not initially detected by radiography may become evident following a relapse in clinical signs after initial apparent success.

References and further reading

Barsanti, J. A. and others (1983) Diethylstilbestrol-induced alopecia in a dog. J Am Vet Med Assoc 182: 63. Frank, L. A. and others. (2010) Variability of oestradiol concentration in normal dogs. Vet Derm 21 (5): 490- 493. Miller, W. H., Griffin, C. G. and Campbell, K. L. (2013) Muller and Kirk’s Small Animal Dermatology, 7th edition:
533-535. Paterson, S. (2008) Manual of Skin Diseases in the Dog and Cat, 2nd edition. Blackwell Scientific: 154.