Unexplained Weight Loss: Causes & Testing

Unexplained weight loss can be a sign of an underlying medical condition, especially if it is significant (more than 5% of body weight within 6–12 months) and unintentional. Identifying the cause is essential for appropriate treatment.

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Possible Causes of Unexplained Weight Loss

1. Endocrine Disorders

• Hyperthyroidism: Overactive thyroid increases metabolism.
• Diabetes (Type 1 or Type 2): High blood sugar levels cause unintentional weight loss.
• Adrenal Disorders: Conditions like Addison’s disease can lead to weight loss.

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2. Gastrointestinal Disorders

• Malabsorption: Conditions like celiac disease or Crohn’s disease impair nutrient absorption.
• Ulcers or Gastritis: Stomach pain or nausea may reduce appetite.
• Liver or Pancreatic Disease: Impairs digestion and metabolism.

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3. Chronic Infections

• Tuberculosis (TB): Causes significant weight loss along with other symptoms like fever and night sweats.
• HIV/AIDS: Affects the immune system and can lead to wasting syndrome.
• Parasitic Infections: Parasites can rob the body of nutrients.

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4. Cancer

• Weight loss is a common early symptom of many cancers, including:
  • Lung cancer
  • Pancreatic cancer
  • Gastrointestinal cancers (e.g., stomach, colon)

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5. Mental Health Conditions

• Depression: Can reduce appetite or interest in food.
• Anxiety: Heightened stress may lead to weight loss.
• Eating Disorders: Conditions like anorexia nervosa may not always be initially apparent.

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6. Neurological Disorders

• Parkinson’s Disease or Dementia: May impair swallowing or reduce interest in eating.

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7. Autoimmune Diseases

• Rheumatoid Arthritis: Inflammation increases energy expenditure.
• Lupus: Causes systemic inflammation and appetite loss.

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8. Substance Abuse

• Alcohol, illicit drugs, or overuse of certain medications (e.g., stimulants) can lead to poor appetite or nutrient absorption.

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9. Medications

• Side effects of medications (e.g., chemotherapy, antidepressants) can suppress appetite or cause nausea.

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10. Aging

• Loss of muscle mass (sarcopenia), reduced appetite, or other age-related conditions may lead to weight loss.

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Testing for Unexplained Weight Loss

1. Initial Evaluation

• Medical History: Includes questions about diet, lifestyle, medications, and stress.
• Physical Exam: Checks for signs like swollen lymph nodes, thyroid abnormalities, or gastrointestinal issues.

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2. Laboratory Tests

• Blood Tests:
  • Complete Blood Count (CBC): Detects anemia or infection.
  • Thyroid Function Tests (T3, T4, TSH): Checks for hyperthyroidism.
  • Blood Glucose: Screens for diabetes.
  • Liver and Kidney Function Tests: Identifies organ dysfunction.
• Nutritional Markers:
  • Vitamin levels (e.g., B12, D) and electrolytes.
• Inflammatory Markers:
  • C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR).

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3. Imaging Studies

• X-rays or CT Scans: Look for tumors, infections, or organ abnormalities.
• Endoscopy/Colonoscopy: Investigates gastrointestinal issues.

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4. Specialized Tests

• HIV or TB Testing: If infection is suspected.
• Autoimmune Panels: For conditions like lupus or rheumatoid arthritis.
• Cancer Screening: Biopsies or tumor markers based on symptoms.

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When to See a Doctor

• Weight loss >5% of body weight in 6–12 months without explanation.
• Accompanied by symptoms like fatigue, pain, fever, or digestive issues.
• Persistent appetite changes or gastrointestinal problems.

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