Diagnostic Criteria of Anorexia Nervosa

  • Definition: A psychiatric disorder marked by significantly low body weight, intense fear of weight gain, and a disturbance in body image.
  • Diagnosis (all four criteria):
    1. Low body weight: At least 15% below ideal or BMI ≤18.5 kg/m².
    2. Intense fear of weight gain or becoming fat.
    3. Severe body image disturbance: Weight/shape is the main measure of self-worth.
    4. Amenorrhea in females: Absence of ≥3 consecutive menstrual cycles if post-menarche.

Subtypes

  • Restricting: Weight loss through strict diets and/or excessive exercise.
  • Binge-eating/Purging: Recurrent binge eating followed by self-induced vomiting, laxative use, or diuretic use.

Epidemiology

  • Prevalence: Affects ~1% of women over a lifetime; rare in men.
  • Age of Onset: Typically mid to late adolescence; rarely after age 40.

Etiology & Risk Factors

  • Multifactorial:
    • Cultural: Societal emphasis on thinness.
    • Biological: Twin studies suggest genetic predisposition.
    • Psychological: Stressful events may trigger onset; perfectionism is common.
  • Neurohormonal Changes: Result from malnutrition rather than cause it (e.g., low leptin, high cortisol).

Clinical Features

  1. Weight-Loss Behaviors
    • Restrictive eating patterns or binge-purge cycles.
    • Persistent fear of fatness, fixation on thinness.
  2. Physical Examination
    • Low BMI (≤18.5 kg/m²).
    • Vital Signs: Hypotension, bradycardia, hypothermia.
    • Skin/Hair:
      • Lanugo on cheeks/arms,
      • Dry or slightly yellowish skin (β-carotene),
      • Parotid enlargement if purging.
    • GI Complaints: Constipation.
  3. Laboratory Findings
    • Mild anemia (normocytic normochromic),
    • Mild leukopenia,
    • Electrolyte imbalances with purging (e.g., hypokalemia, metabolic alkalosis),
    • Mildly elevated liver enzymes,
    • Normal/low-normal glucose,
    • Possible increased serum cholesterol.
  4. Endocrine Changes
    • Hypothalamic Amenorrhea: Low LH, FSH, estradiol (low leptin from low fat mass).
    • Thyroid: Euthyroid sick syndrome (low T3, high rT3, low-normal TSH).
    • Cortisol: Elevated but no Cushingoid signs.
    • GH/IGF-1: Increased GH, low IGF-1.
    • Bone Density: Decreased; osteopenia/osteoporosis common.

Differential Diagnosis

  • Medical: HIV, inflammatory bowel disease, diabetes, CNS lesions.
  • Psychiatric: Major depression, other eating disorders (e.g., bulimia).

Summary

  • Key Aspects: Substantial underweight status, persistent fear of fatness, distorted body image, and amenorrhea in women.
  • Systemic Effects: Starvation-driven neuroendocrine changes, including growth and reproductive hormone suppression, and bone density loss.
  • Management: Focus on medical stabilization, nutritional rehabilitation, psychological treatment, and addressing any comorbidities.

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