Squamous metaplasia of the prostate and diffuse alopecia in a 13-year-old castrated dog due to chronic ingestion of exogenous estradiol

Introduction. A 13-year old whippet with a generalized progressive alopecia since 2 years was referred to our clinic to perform a low-dose dexamethasone stimulation test and abdominal ultrasound to exclude or confirm Cushing disease. The dog had previously been treated with trilostane for 4 months without having any positive effects. Earlier blood analysis showed no significantly abnormalities and ACTH stimulation test was negative. Having bilateral cryptorchidism, the dog was castrated at young age.
Clinical findings and treatment. Abdominal ultrasound revealed a slightly enlarged right adrenal gland (diameter of 1 cm at the cranial part). The prostate was enlarged and heterogeneous with multiple anechogenic cavities, indicating hormonal stimulation. Craniad the prostate and ventrally of the bladder, a hypoechogenic, oval structure (3 cm by 1.7 cm) could be seen, and was suspected to be a remaining cryptorchide testicle. Fine needle aspiration however showed that the structure contained a thick purulent liquid, with large amounts of polymorhonuclear white blood cells.
Blood analysis revealed a leukocytosis (29370/mm3) with neutrophilia (23202/mm3). Low-dose dexamethasone test definitely excluded Cushing disease (basal cortisol levels 2,17 µg/dl; cortisol at 4 and 8 hours < 1 µg/dl). A prostatic wash was performed and revealed a severe prostatitis and presence of keratinized prostatic cells, indicating a squamous metaplasia of the prostate. Measurement of seric LH levels (LH Witness®, Synbiotics) showed an LH concentration lower than 1 ng/ml, indicating a hormonal negative feedback on the hypothalamo-hypophyso-gonadal axis.
After a more thorough anamnesis, it became clear that the dog was licking and ingesting a transdermal estradiol containing cream (Estrogel®) from his owner, since two years, causing his symptoms.
The dog was put on antibiotic treatment for the prostatitis (enrofloxacine 10 mg/kg SID) and underwent surgery to excise the abscess cranial of the prostate. The two ductuli deferentes were attached to this structure. Histopathological analysis revealed this tissue to be embryological remanents or a morphological anomaly with a urogenital origin.
Control after 4 weeks showed that the prostate slightly decreased in volume, however, anechogenic cavities where still present of which one increased in volume. The alopecia was still present as well, both probably due to a prolonged action of the estrogens.
Conclusion. Even though injectable estrogen preparations are not longer available in veterinary medicine in Europe, a thorough anamnesis towards other exogenous estrogen sources is still necessary and can reduce the number of supplementary exams performed.