CHAPTER 28 HYPOTHYROIDISM 419
“Tragic” facial expression
Significant hyperkeratosis/seborrheic dermatitis
Hyperpigmentation, lichenification, and comedones in alopecic regions
Bacterial folliculitis (Figure 28.10).Recurrent pyoderma: caused by decreased T cell function and humoral immunity as
well as by alterations in the local epithelial environment.
Malasseziadermatitis.
Demodicosis.
Otitis externa.
Poor wound healing.
Bruising.
Pruritus uncommon unless associated with secondary infection.
DIFFERENTIAL DIAGNOSIS
Hyperadrenocortisolism: often associated with other systemic symptoms; exogenous
or endogenous source.
Sex hormone abnormalities (adrenal, extraadrenal, and gonadal).
Follicular dysplasia.
Telogen effuvium.
Alopecia due to systemic illness or secondary to medical therapy.
Pattern alopecia including cyclic flank alopecia.
Primary keratinization disorder.
DIAGNOSTICS
CBC/Biochemistries
Normocytic, normochromic, nonregenerative anemia (approximately 30% of cases).
Fasting hypercholesterolemia (greater than 75% of cases).
Fasting hypertriglyceridemia; gross lipemia.
Thyroid Hormone Concentration
Total T 4 :
Reports both protein-bound and free T
4
Usually below normal range in hypothyroidism
Tests ability of the thyroid gland to produce hormone
Low T
4 measurement must be associated with appropriate clinical signs for pre-
sumption of hypothyroidism; additional tests (e.g., fT 4 , TSH measurement) rec-
ommended to aid diagnosis
Autoantibodies to T
4 will affect results
Lower ranges in certain breeds (e.g., greyhound)
Wide fluctuations occur in normal dogs.
Declines noted with age, estrus, pregnancy, obesity, and malnutrition