340 DISEASES/DISORDERS
distal extremities; primary coat lost first, resulting in patchy retention of the under-
coat; complete alopecia eventually develops.Variable secondary seborrhea, pruritus, bacterial folliculitis, and comedones.
Epidermal and dermal atrophy; mild lichenification and scaling.
Systemic signs (polyuria/polydypsia/polyphagia) usually not present; urinary incon-
tinence may occur in estrogen-responsive cases.
DIFFERENTIAL DIAGNOSIS
Hypothyroidism
Hyperadrenocorticism
Bacterial folliculitis
Demodicosis
Follicular dysplasia: color dilution alopecia, black hair follicular dysplasia
Pattern alopecia: dachshund, Boston terrier, greyhound, water spaniel, chihuahua
Cyclical flank alopecia: boxer, English bulldog, Airedale
Postclipping alopecia
Telogen defluxion
Keratinization disorder
DIAGNOSTICS
CBC/biochemistries/urinalysis: normal except as associated with hypothyroidism or
hyperadrenocorticism; anemia and/or bone marrow hypoplasia or aplasia with hyper-
estrogenism.Serum sex hormone concentrations: often normal; treat according to suspected diag-
nosis based on clinical signs and ruling out other disorders.
Serum estradiol: sometimes elevated in male dogs with testicular tumors or female
dogs with cystic ovaries; normal daily fluctuations of estradiol make interpretation
of estradiol concentrations difficult; prolonged elevation demonstrated by repeated
tests more conclusive.Exposure to human topical hormone replacement therapy may or may not cause
serum estradiol, progesterone, or testosterone levels to be elevated above normal
despite having dramatic effects on the skin.ACTH stimulation test or LDDS test: exclusion of hyperadrenocorticism.
Serum thyroxine, fT4, and TSH: exclusion of hypothyroidism.
ACTH stimulation test with measurement of adrenal sex hormones: may indicate
overproduction of cortisol precursors.
Dermatohistopathologic changes commonly associated with endocrine dermatoses:
telogenization of hairs, follicular keratosis, tricholemmal keratinization (flame folli-
cles), epidermal and dermal atrophy, sebaceous gland atrophy; usually distinct from
changes associated with pattern baldness and follicular dysplasia.Abdominal ultrasound: adrenal gland hyperplasia or neoplasia, and gonadal
neoplasia.