Endocrine Alopecia in Dogs

Introduction

The hair follicle is influenced by hormonal activity in a variety of ways and is capable in its own right of synthesizing and converting a wide range of hormones. In the rat, it has been demonstrated that estradiol, testosterone and the steroids produced by the adrenal glands delay the start of the anagen (active growth) phase, while thyroid hormones accelerate follicular activity (1). In the dog, certain endocrinopathies (hypothyroidism, hypercortisolism), functional neoplasia of the gonads (hyperestrogenism) and certain follicle dysplasias (cyclic alopecia of the groin) are associated with alterations of the follicular cycle and present as symmetrical alopecia.

The aim of this article is to provide an up-to-date summary on the pathogenesis and the dermatological signs of hormonal diseases that cause alterations in the follicular cycle, and offer a diagnostic approach for dogs with non-pruritic symmetrical alopecia. [...]

Key Points

• Non-pruritic symmetrical alopecia in dogs is a clinical condition commonly associated with endocrinopathies, functional neoplasia of the gonads, follicular dysplasia and idiopathic alopecia.
• Although unlikely, infectious conditions that can affect the hair follicle, in particular demodicosis, should be excluded.
• Ultrasonography is advisable for female dogs presenting with enlarged vulva and teats and for male dogs that are either cryptorchid or have alterations in the size/consistency of the testicles.
• The initial laboratory examinations should include hematology, CBC and urine examination.
• Dynamic assessment of thyroid function must be carried out after any adrenal function test.
• Cutaneous biopsy may help identify follicular dysplasia or an idiopathic alopecia (Alopecia X)