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anagen or prolonging telogen. While hormonal disorders can result in non-pruritic symmetrical non-inflammatory alopecia, there are also many other causes.
Diagnostic work up
Signalment and history
Age
· Middle aged to older dogs for hormonal disorders
· Young dogs for follicular dysplasia and pattern bald- ness
Breed
· Hyperadrenocorticism: predisposed breeds include Miniature Poodles, Dachshunds and Boston Terriers
· Hypothyroidism: predisposed breeds include Boxer, Old English Sheepdogs and Golden Retrievers
· Plush coated breeds such as Pomeranian, Alaskan Malamute, Samoyed and Siberian Husky suggestive of hair cycle arrest
· Recurrent cyclic flank alopecia: predisposed breeds include Airedale, Boxers and Schnauzers.
· Colour dilution alopecia affect dilute (blue or fawn) coated breeds such as Staffordshire Bull Terriers and Dobermans
· Pattern baldness: predisposed breeds include Dachshunds and whippet
History
· Polyuria, polydipsia and polyphagia and history of ex- ogenous corticosteroids for e.g. allergies suggestive of hyperadrenocorticism
· Weight gain and lethargy suggestive for hypothyroid- ism
· History of owner using topical estrogen hormonal replacement therapy OR use of estrogen for uri- nary incontinence, could indicate estradiol induced alopecia
· Feminisation behaviour in intact dogs e.g. nursing or attraction of male dogs to other males could indicate sex hormone dermatosis
· History of seasonal alopecia and regrowth could indi- cate recurrent cyclic flank alopecia
· Prior stressful events e.g. disease, surgery or preg- nancy could suggest anagen (alopecia within days) or telogen (usually 1-3mths prior to alopecia) effluvi- um
Physical and dermatological examinations
· Thinning of skin, comedones, hepatomegaly, pen- dulous abdomen and calcinosis cutis suggestive of hyperadrenocorticism
· Overweight, bradycardia and facial myxedema sug- gestive of hypothyroidism
· Gynecomastia, pendulous prepuce, vulvar enlarge- ment and/or preputial dermatosis suggestive of hyperestrogenism
· Well demarcated alopecia and hyperpigmentation affecting lateral flanks/thorax suggestive of recurrent cyclic flank alopecia
· Alopecia affecting only black coloured hair is sug- gestive for black hair follicular dysplasia
· Palpate testes for asymmetry suggestive of testicular tumour
Diagnostic tests
· Based on clinical suspicion to allow ranking of ddx and diagnostic steps
Your Singapore, the Tropical Garden City
· Trichogram
· o Irregular pigment granules along hair shafts sug-
gestive of colour dilution alopecia
· o All hair bulbs in telogen phase for endocrine alopecia
· Complete blood count, biochemistry, urinalysis and culture may provide clues but are not specific e.g.
· o Stress leukogram with elevated liver enzymes (especially ALP), hyposthenuria or isosthenuria for hyperadrenocorticism
· o Non regenerative anemia and elevated fasting cholesterol for hypothyroidism
· o Anemia, thrombocytopenia, leucocytosis or leuco- penia due to myelosuppression by estrogen
Endocrine testing
· o Hypothyroidism e.g. fT4 (ED), TT4, TSH
· o Hyperadrenocorticism: Screening (e.g. LDDST, ACTH simulation test) and differentiating (e.g. LDDST, eACTH, abdominal ultrasound evaluating adrenal glands) tests
· o Baseline and post ACTH stimulation tests for sex hormones (estrogen levels may be normal due to overlap between healthy vs affected dogs)
· Typically if endocrine tests are negative/normal, the next step is to perform skin biopsies for histopathol- ogy and/or castration or ovariohysterectomy with histopathology of testes/ovaries.
Selected References
Wiener DJ, Rufenacht S, Koch HJ, Mauldin EA, Mayer U, Welle MM, Estradiol-induced alopecia in five dogs after contact with a transdermal gel used for the treatment of post menopausal symptoms in women, Veterinary Dermatology, 26:393-e91
Berger DJ, Lewis TP, Schick AE, Miller RI, Loeffler D, Canine alopecia secondary to human topical hormone replacement therapy in six dogs, Journal of the American Animal Hospital Association, 2015, 51:136-142
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