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):
- Low body weight: At least 15% below ideal or BMI ≤18.5 kg/m².
- Intense fear of weight gain or becoming fat.
- Severe body image disturbance: Weight/shape is the main measure of self-worth.
- 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
- Weight-Loss Behaviors
- Restrictive eating patterns or binge-purge cycles.
- Persistent fear of fatness, fixation on thinness.
- 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.
- 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.
- 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.