As noted in Table 62, the diagnostic analysis of weight loss is best accomplished by applying physiology. Food and oxygen must be properly and regularly brought into the body (intake), properly absorbed and circulated to the cells, and properly used; the waste products must then be excreted in order for weight to be maintained. The storage of food is essential to maintain weight when food is not being regularly ingested. Finally, there must be minimal excretion of sugar, protein, electrolytes, and water to maintain weight. Let us explore each of these physiologic functions for possible alterations.
Decreased intake of food results from any disease associated with vomiting, upper intestinal obstruction (e.g., carcinoma of the pyloris), and esophageal obstruction (cardiospasm and carcinoma of the esophagus). Starvation is not uncommon even today, particularly in the elderly population trying to stretch their Social Security checks. Depression, anorexia nervosa, and other psychiatric disturbances may cause weight loss by decreased intake. Central nervous system (CNS) diseases such as cerebral arteriosclerosis may cause disinterest in food and poor chewing and swallowing. Chronic alcoholics do not eat. The absence of one vitamin, as in scurvy or pellagra, may cause weight loss.
|
|
||||||||||||||||||||||||||||||||||||||||||||||||
|
Weakness or paralysis of one or more extremities |
||||||||||||||||||||||||||||||||||||||||||||||||
|
TABLE 62. Weight Loss |
||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||
Decreased intake of oxygen occurs in asthma, emphysema, and other respiratory disorders as well as in CNS diseases that may cause hypoventilation (poliomyelitis).
Decreased absorption of food and electrolytes are common in malabsorption syndrome, pancreatitis, intestinal parasites, and blind loop syndrome. Regional ileitis and tapeworms reduce the absorption of vitamins. The decreased circulation of oxygen is probably the main cause of wasting in CHF, but certainly congestion of the liver and decreased excretion of waste products may play a role. Severe anemia of various causes will inevitably decompensate the delivery of oxygen to the tissues.
The weight loss of cirrhosis (numerous etiologies) is probably due to impaired storage of fat and sugar for use when it is most needed, but the ability to convert protein to sugar and vice versa is also impaired. In glycogen storage and lipid storage diseases, a one-way trip of sugar or fat into the liver is a prominent factor contributing to weight loss. Probably the most common causes of weight loss today are due to the increased use of food in hyperthyroidism and malignancies, but the hypermetabolism of fever and any inflammatory condition (rheumatoid arthritis) is also common.
Neurologic and muscular diseases cause wasting and thus decrease the use of sugar. Impaired use of sugar in diabetes mellitus and other endocrinopathies is a significant cause of weight loss. Various toxins and electrolyte disorders may block the tissue uptake of oxygen (cyanide poisoning, and so forth) and cause weight loss. Disorders of excretion also commonly play a role; thus, one should always look for uremia, pulmonary emphysema, and jaundice.
Finally, there are many disorders already mentioned associated with albuminuria and glycosuria that may be classified under increased excretion of metabolic substances; these, of course, contribute to weight loss. The numerous aminoacidurias and diabetes insipidus should be remembered in this regard.
Approach to the Diagnosis
Weight loss rarely occurs as the only symptom. When it seems to be the only symptom, there is almost invariably a psychiatric disorder such as depression or anorexia nervosa to explain it. More often the diagnosis of weight loss can be made by the other associated symptoms. For example, weight loss with a good appetite, polyuria, and polydipsia should point to hyperthyroidism and diabetes mellitus. Weight loss with weakness and polydipsia but no increase of appetite points to diabetes insipidus. Weight loss, weakness, and loss of appetite suggest the possibility of a malignancy, chronic infectious disease, or endocrine disorder. Weight loss with significant local or generalized lymphadenopathy suggests chronic leukemia, lymphoma, sarcoidosis, or a chronic infectious disease process. Weight loss with hyperpigmentation of the skin suggests Addison disease or hemochromatosis. Weight loss with significant pallor of the skin and mucus membranes suggests a diagnosis of anemia, malabsorption syndrome, and malignancy. Weight loss with jaundice suggests alcoholic cirrhosis, chronic hepatitis, primary or metastatic neoplasm of the liver, or biliary cirrhosis. The initial workup of weight loss should include a CBC, sedimentation rate, chemistry panel, thyroid profile, urinalysis, stool test for occult blood, chest x-ray, and flat plate of the abdomen. If there is fever, the workup of this symptom can be pursued (see page 171). Other tests may be ordered depending on which disease is suspected. Before ordering a battery of tests, it may be wise to get a psychiatric consult and make sure there is not a “supratentorial” cause for the problem.
Other Useful Tests
1. Tuberculin test (tuberculosis)
2. Glucose tolerance test (diabetes mellitus)
3. Serum amylase and lipase levels (chronic pancreatitis, pancreatic neoplasm)
4. Drug screen (drug abuse)
5. HIV antibody titer (AIDS)
6. Stool for fat and trypsin (malabsorption syndrome)
7. Stool for ova and parasites (parasites infestation)
8. D-Xylose absorption test (malabsorption syndrome)
9. Urine 5-hydroxyindole acetic acid (5-HIAA) (carcinoid syndrome, malabsorption syndrome)
10. Bone scan (metastatic malignancy)
11. CT scan of the abdomen (malignancy, abscess)
12. Lymphangiogram (Hodgkin lymphoma, metastatic malignancy)
13. CT scan of the brain (pituitary tumor)
|
|
|
Weight loss |
14. Lymph node biopsy (lymphoma, malignancy)
15. Serum antidiuretic hormone (ADH) level (diabetes insipidus)
16. Serum cortisol level (Addison disease, hypopituitarism)
17. Serum growth hormone, LH or FSH (Simmonds disease)
Case Presentation #87
A 26-year-old singer in a rock band complained of losing 32 pounds over the past year. She denies weakness, polyuria, polydipsia, or diarrhea. Her physical examination is unremarkable except for pale conjunctiva.
Question #1. Utilizing your knowledge of physiology and biochemistry, what is your differential diagnosis?
Stool analysis for fat content, ovum and parasites, and occult blood was normal. A gastrointestinal (GI) series and barium enema were normal. Complete laboratory studies revealed only a microcytic hypochromic anemia.
Question #2. What is your diagnosis now?
