Endocrine (Hormonal) Disorders
Common endocrinopathies in the dog include hypothyroidism and Cushing's disease (hyperadrenocorticism). These two conditions can cause loss of hair, brittle hair, changes in hair color, and skin infections. Seasonal flank alopecia is another disease that also may involve hormones.
Cats, also can have skin and hair coat changes due to endocrine disorders. Cats may have similar changes to the hair and coat as dogs from hyperthyroidism and thymomas.
Blood tests may be utilized to diagnose these disorders. In certain cases a skin biopsy may be needed.