Canine Alopecia Secondary to Human Topical Hormone Replacement Therapy in Six Dogs

Abstract

Alopecia is a common presenting complaint in veterinary medicine and is known to occur secondary to numerous primary conditions. In this report, six unrelated dogs from three households were subsequently determined to have developed alopecia as a result of accidental transdermal exposure to their owners' topical hormone replacement therapy (THRT). All cases presented with alopecia ranging in duration from 2 mo to 2.5 yr. All dogs demonstrated alopecia affecting the ventral neck, thoracic and abdominal surfaces, proximal lateral extremities, and lateral trunk. At the time of initial presentation, five of six dogs were also noted to have physical exam findings suggestive of feminization. In all cases, serum total thyroxine was within normal reference range. Affected skin was biopsied in five dogs, and all samples demonstrated four similar histological characteristics: basal melanosis, epidermal and infundibular follicular hyperkeratosis, kenogen hair follicles, and small sebaceous glands. All dogs had elevated baseline estradiol levels, and four dogs had concurrent elevations of baseline progesterone. Average time to onset of clinical signs in those dogs was 5.5 mo after the owners started THRT. Following discontinuation of THRT by the owners, all dogs had complete resolution of their clinical signs by 5.5 mo.

Estradiol‐induced alopecia in five dogs after contact with a transdermal gel used for the treatment of postmenopausal symptoms in women

“…The findings in this case series are similar to those in a recent publication . Exposure to an estradiol gel used by the owners as treatment for their postmenopausal symptoms resulted in estradiol‐induced alopecia in five dogs.…”

“…The estradiol gel was used by all owners for a long period of time (exact data are not available) but, as also shown in another study, the time span between exposure to the gel and the development of alopecia was variable (ranging from few months to 3 years). Nevertheless, in all cases a close relationship between administration of the gel, close contact with the owner and development of alopecic areas was found.…”

“…Alopecia secondary to human topical hormone replacement therapy has been described where dogs had elevated baseline estradiol concentrations and most showed signs of feminization …”

Approach to generalised alopecia in dogs: use and abuse of endocrine testing

“…This highlights the importance of sometimes going back to the owner to ask more specific questions about the lifestyle. Women using a transdermal gel for the treatment of postmenopausal symptoms may not realise that it can be absorbed by the dog's skin and lead to alopecia (Berger and others 2015, Wiener and others 2015).…”

Dermatological topical products used in the US population and their toxicity to dogs and cats

“…4 Unlike oral medications, dermatological topicals also can be licked off the pet owner's skin and/or absorbed transdermally by the pet. 5 Some drugs used in dermatological topicals that are well-tolerated in people may be toxic to dogs or cats because of species differences in toxicosis. For example, oral diclofenac has an extremely high ulcerogenic potential in dogs, 6 but not in people.…”