Weight Loss
The significance of weight loss should not be underestimated: In about one-third of patients, there is no specific cause, but in the rest, a serious underlying pathology is found. The minority of these are psychiatric; 90% have organic illness. Thorough assessment from the start is the rule.
Differential diagnosis
Common Diagnoses
- ‘Normal’ Stressful Life Events without Psychiatric Illness (e.g. Changing Job, Divorce, Redundancy, Bereavement, Exam Pressure)
- Clinical Depressive Illness
- Eating Disorders: Anorexia Nervosa and Bulimia Nervosa
- Hyperthyroidism: Thyrotoxicosis and Iatrogenic (Excess Thyroid Replacement)
- Malignancy Anywhere
Occasional Diagnoses
- Anxiety (of whatever Cause)
- Any Terminal Illness (e.g. Malignancy, Motor Neurone Disease)
- Substance Misuse: Alcohol, Opiates, Amphetamines, Laxatives
- Organ Failure: Cardiac, Renal and Hepatic
- Undiagnosed Diabetes Mellitus
- Chronic Inflammatory Conditions (e.g. RA, SLE)
- Gastrointestinal Disease (e.g. Peptic Ulcer, Inflammatory Bowel Disease, Coeliac Disease, Parasites)
Rare Diagnoses
- Any Chronic Infection (Especially Tuberculosis)
- Endocrine: Addison’s Disease, Phaeochromocytoma
- AIDS
- Malnutrition (Rare in Developed Countries, Common Worldwide)
Ready reckoner
Key distinguishing features of the most common diagnoses
| Normal Stress | Depression | Eating Disorders | Hyperthyroidism | Malignancy | |
|---|---|---|---|---|---|
| Mild Anxiety | Yes | Possible | No | No | No |
| Loss of Appetite | Possible | Yes | No | No | Yes |
| Distorted Body Image | No | No | Yes | No | No |
| Recurrent Problem | Yes | Possible | Possible | Possible | No |
| Severe Malaise | No | Yes | Possible | Possible | Yes |
Possible investigations
Likely: Urinalysis, FBC, ESR/CRP, TFT, U&E, LFT, CXR, blood glucose or HbA1c.
Possible: Autoimmune screen, HIV test, CA-125, bowel investigations such as FIT, faecal calprotectin or antiendomysial and anti-gliadin antibodies, other hospital-based investigations.
Small Print: None.
- Urinalysis: For possible undiagnosed diabetes; proteinuria in renal failure.
- FBC and ESR/CRP: Hb may be reduced and ESR/CRP elevated in malignancy and any chronic disorder. Raised platelets associated with oesophageal or stomach cancer.
- U&E: Abnormal in renal failure and sometimes in eating disorders; sodium reduced, potassium and urea elevated in Addison’s disease.
- TFT: Will confirm hyperthyroidism.
- LFT: Deranged in alcoholism and liver disease.
- Blood glucose or HbA1c: To confirm diabetes.
- Autoimmune screen: May be helpful in suspected connective tissue disorder.
- HIV test: If AIDS suspected.
- CA-125: If ovarian cancer is a possibility.
- Bowel investigations such as FIT, faecal calprotectin or anti-endomysial and anti-gliadin antibodies: If carcinoma, IBD or coeliac disease suspected.
- CXR: May reveal carcinoma, TB, lymphadenopathy or cardiac failure.
- Other investigations (usually hospital-based) may be required according to the symptoms accompanying the weight loss and the results of preliminary investigations.
Top Tips
- Weight loss needs to be taken seriously but can be complex and time-consuming to assess. If presented as a ‘by the way’ at the end of a consultation for some other matter, it is reasonable to reverse the normal approach by arranging basic blood tests and urinalysis first, and booking a follow-up appointment, with the results, for a more complete assessment.
- Establish whether episodes of weight loss have happened before. Patients, or their records, may indicate, for example, that they always lose weight when stressed.
- Check that the patient really has lost weight. The history may not be clear, and there is often a record available (e.g. new patient check or health promotion data) of previous weight.
- Look at the patient. The obviously cachectic will have significant disease and require urgent and thorough investigation.
Red Flags
- Rapid weight loss with malaise and respiratory or gastrointestinal symptoms strongly suggest a physical cause.
- Think of eating disorders in young females – look for acid dental erosion on palatal surfaces of upper teeth as a giveaway sign of recurrent vomiting.
- Weight loss in a child is caused either by significant organic pathology or emotional abuse. Look out for signs of non-accidental injury (NAI) during physical examination.
- Depression with weight loss is a difficult problem; it may be the primary cause or the change in mood may be secondary to some physical illness. Either way, don’t overlook significant depression while you arrange investigations; there is nothing to be lost in starting antidepressants while you continue to exclude a physical cause, so long as you explain your strategy to the patient.