Patients who suffer from pathological conditions that justify weight loss usually have signs and symptoms that make it possible to suspect the affection of a certain organ, apparatus or body system. Tumors of the digestive system, including those of the pancreas and liver, can impair food intake early and cause weight loss before other symptoms appear. Lung cancer can present as postobstructive pneumonia with dyspnea, or cough and hemoptysis, but it is also usually symptom-free and should be suspected even in nonsmokers. Depression and isolation can lead to significant weight loss, particularly in the elderly. In chronic obstructive pulmonary disease and congestive heart failure, anorexia and increased energy expenditure at rest may appear. Weight loss can be the first manifestation of some infectious diseases, such as HIV infection, tuberculosis, endocarditis, and fungal and parasitic infections. Hyperthyroidism or pheochromocytoma increase basal metabolism; the elderly with apathetic hyperthyroidism may present with weight loss and weakness, with few other manifestations of thyrotoxicosis. New-onset diabetes mellitus is often accompanied by weight loss due to glycosuria and loss of the anabolic effects of insulin.