Hypothyroidism:

This condition, caused by an overactive thyroid gland, is increasing in North America and can only be diagnosed through blood tests. Hyperthyroidism often causes irreversible heart, liver, and kidney damage, so early detection is critical. Cats that lose weight despite a normal to increased appetite, experience chronic vomiting or diarrhea, have increased thirst and/ or urination, experience difficulty breathing, or have a dry, dull hair coat should be tested for thyroid disease. Several safe and effective treatments are available.