338 DISEASES/DISORDERS
CLINICAL FEATURES
Diabetes Mellitus and Hyperthyroidism
Diabetes mellitus and hyperthyroidism are common endocrinopathies in the cat.
Changes in the hair coat and skin are caused by alterations in metabolism as well as
by changes in grooming behavior.
Metabolic alterations may result in increased incidence of pyoderma and seborrheic
dermatitis.
Diabetic cats will often have excessive scales and a dull, disheveled-appearing hair
coat (Figure 22.1).
Xanthomatosis: excessive accumulation of lipid in the skin; associated with diabetes
mellitus in the cat (rarely dog) (Figure 22.2).
Hyperthyroidism may result in overgrooming, causing patches of hair loss, as well as
seborrheic dermatitis (Figure 22.3).
Alopecia X
Synonyms: growth hormone (GH)-responsive alopecia; adrenal sex hormone imbal-
ance of plush-coated breeds; castration-responsive dermatosis; pseudo-Cushing’s syn-
drome; adrenal hyperplasia-like syndrome; and atypical Cushing’s syndrome.May be caused by elevated levels of progesterone or androgen or their intermediaries
causing direct effects on the hair follicle or decreased GH production.
Hyposomatotropism is an inconsistent finding.
Adrenal sex hormone imbalance of plush-coated breeds and adrenal hyperplasia-
like syndrome may result from adrenal 21-hydroxylase enzyme deficiency producing
excessive secretion of steroid hormone precursors.Genetic factors and hair follicle receptor defects (and/or stimulation) are current con-
cepts in the development of and treatment for hair cycle arrest in these patients.
Predisposed breeds: miniature poodle and plush-coated breed such as pomeranian,
chow chow, Akita, samoyed, keeshonden, Alaskan malamute, and Siberian husky
(Figures 22.4, 22.5).Occurs primarily between 1 and 5 years of age.
Intact or neutered male and female dogs.
Usually asymptomatic lack of hair coat growth and loss of primary hairs.
Noninflammatory and symmetric hair loss that spares the head and extremities (see
Figures 22.4, 22.5).
Often accompanied by striking melanoderma.
Secondary bacterial folliculitis andMalasseziadermatitis uncommon.
Hypopituitary dwarfism: distinct from the syndromes considered in alopecia X; defect
in or destruction of secretory capability of the adenohypophyseal cells; may be asso-
ciated with other hormone deficiencies; seen in German shepherds, spitz, miniature
pinscher, carnelian bear dog; noted by 3 months of age (Figure 22.6).