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Anorexia nervosa

Definition
  • Eating disorder characterised by:
    • low body weight (<85% ideal body weight)
    • disturbed body image
    • dietary practices to maintain low weight
    • fear of gaining weight
    • lack of menstrual periods for ≥3 months
  • Frequent exercise is common
Risk Factors
  • Female gender
    • About 70% of AN patients are female
      • But 90% of patients seen are likely to be female due to reduced presetation in males
    • Pressures to achieve cultural ideals of beauty are placed primarily on women, less so on men
    • Anorexia in males may be under-reported.
  • Adolescence and puberty
    • Onset peaks at ages 14.5 and 18 years
      • 5-fold incidence in the teenage versus older female population
    • Onset in women in their 20s and 30s is increasing, indicating a possible trend change
  • Obsessive and perfectionist traits
    • Strongly linked to condition in case-study research
    • Non-specific risk for developing both anorexia and bulimia
  • Exposure to western media
    • Disease prevalence in West is 0.1% to 5.7% in females
    • Culture-change syndrome
      • Immigrants moving to western-influenced cultures exhibit a higher incidence
  • Middle and upper socioeconomic classes
    • Linked with increased risk of eating disorders with the exception of binge eating disorder
    • Pressures to achieve success in the eyes of society increase with status
  • Identical twin affected
    • Studies showed a 6.6% risk of an identical female twin developing disease
    • Fraternal twins show no increased risk, leading to conclusion that the link is biological
  • Family dysfunction
    • Family dysfunction influences psychological makeup of anorexics and is potentially involved in the condition's development
Differential diagnosis
  • Bulimia nervosa
    • Complain of bloating, abdominal pain, sore throat, and a feeling of fullness.
  • Depression
    • Often show poor concentration and poor self-esteem, not solely linked to weight gain or loss.
  • Hyperthyroidism
    • Weight loss with additional symptoms of heat intolerance, hyperactivity, polyuria, sweating, nausea with vomiting, diarrhoea, and tremors.
  • Type 1 diabetes mellitus
    • History of blurred vision, polyuria, polydipsia, and polyphagia are common with weight loss, but without purging.
  • Crohn's disease
    • May have abdominal pain, bloody stools, and possibly arthritic pain in addition to weight loss
    • Patients do not avoid food for fear of gaining weight.
    • Colonoscopy with biopsy will show inflammatory tissue changes.
  • Ulcerative colitis
    • May have abdominal pain, bloody stools, and possibly arthritic pain in addition to weight loss.
    • Colonoscopy with biopsy will show inflammatory tissue changes.
  • Obsessive-compulsive disorder (OCD)
    • OCD often presents similarly, with ritualised eating habits.
    • However, OCD is characterised by obsessions unrelated to food, such as a fear of death.
    • Medication may be effective, unlike in anorexia
  • Cancer (any type)
    • Weight loss unintentional without fear of weight gain or body image disruption.
    • FBC may show anaemia.
    • If warranted, biopsy, cytology, and imaging should be carried out.
  • HIV infection
    • May have a history of fever, headache, aching muscles, sore throat, and often swollen lymph nodes, mouth and oesophageal ulcers, and rash in addition to weight loss.
Epidemiology
  • About 0.3% of people in westernised countries, with about 0.5% to 1% of college-aged women, are affected
  • It is estimated that 3 in 10 patients are male
    • Many males do not present for treatment
    • Thus, about 90% of patients diagnosed are female
    • The incidence of homosexuality among anorexic men is 25% to 58%, depending on the study.
  • The risk of onset is highest in late adolescence, with 40% of new cases found between ages 15 and 19 years
  • Only one third seek medical care
  • Patients show a 25% lifetime prevalence of concomitant OCD and a 50% to 70% prevalence of dysthymia
  • White women are more likely to develop anorexia than black women
  • Multiple cross-cultural studies have linked increases in eating disorders to western media exposure and ideals
Aetiology
  • The specific cause is unknown at present
  • Several neurotransmitters have been implicated in the aetiology of AN
    • However studies have been generally difficult to interpret
    • Changes seen may be a consequence of semi-starvation, rather than the cause of semi-starvation
  • Evidence suggests that genetic factors are important in the development of AN
    • Heritability estimates range from 50% to 75% using a wide variety of assessment strategies
Clinical features
  • Weight loss
    • <85% of normal weight for height and age.
    • BMI is usually <17.5 kg/m^2
  • Fear of gaining weight
    • Avoids and refuses intervention to gain weight
  • Disturbed body image
    • Indicates either abnormally large size of certain body parts or failure to acknowledge overall thinness
  • Calorie restriction
    • In restrictive type, calorie intake is lowered to 300 to 700 kcal a day
  • Bingeing and/or purging
    • May exist as part of bingeing and/or purging subtype
    • May conceal this detail in history
    • Physical signs of dental erosion and hand calluses must be relied upon
  • Misuse of laxatives, enemas, and/or diuretics
    • Part of bingeing and/or purging subtype
  • Amenorrhoea 
    • Whether patient is taking oral contraceptives should be determined
  • Decreased subcutaneous fat 
    • Bony structures may protrude due to the extreme lack of body fat
  • Fatigue and weakness 
    • Specifically related to weight loss
  • Poor concentration
    • Specifically related to weight loss
  • Fainting
    • Often related to orthostatic hypotension and bradycardia
  • Constipation 
    • Due to a decrease in gastrointestinal motility related to decreased consumption of calories
  • Lanugo body hair 
    • Development of fine body hair
  • Orthostatic hypotension
    • Low fluid status may result in slow re-equilibration from sitting to standing
    • May result from hypovolaemia and/or low cardiac output
  • Bradycardia 
    • Due to an adaptive response to weight loss and negative energy balance
  • Dehydration 
    • Due to an inadequate intake of fluids
  • Cardiac arrhythmias 
    • May be due to a decreased heart size as a result of weight loss
  • Hair loss 
    • Occurs due to inadequate nutrition
  • Shorter stature 
    • A sign of poor growth and nutrition in adolescents
  • Hypothermia
    • Common in severe disease
  • Eroded dental enamel 
    • Sign of bingeing and/or purging
    • May be associated dental abscesses or caries
  • Scars on dorsum of hand 
    • Repetitive forcing of the hand down back of the throat may cause scars
  • Dependent oedema
    • May be due to low protein stores, resulting in fluid shift
  • Increased fractures 
    • More common in affected people in their 20s
Pathophysiology
  • The pathophysiology is currently unknown
  • A susceptible person, whether through biology, societal patterns, or behavioural makeup, begins dieting
    • 35% of those dieting progress to pathological eating habits
    • 20% to 25% go on to partial or full-blown eating disorders
  • Weight loss gives positive reinforcement to continue avoidance of food, intense exercise, or bingeing and/or purging behaviours
  • The effect of low weight and starvation leads to nutritional imbalances and psychological changes
  • Due to the patient's tendency towards obsessive behaviours and rigid thought patterns, the patient maintains the anorexic cycle
  • The act of starvation and weight loss may provide a sense of pride and positive drive for the patient
  • Any life stresses, often interpersonal in nature, are avoided with the obsessive focus on food and weight management
    • A sense of controllable satisfaction and success prompts continuation
    • The patient gains confidence and resists walking away from the safety of routine
  • Psychologically speaking, AN relieves generalised anxiety, which takes the form of an easy-to-identify fear of food
    • The fear of gaining weight leads to avoidance of food, which leads to relief of anxiety through weight loss
  • Additionally, physiological changes propagate the disease and continual relapses
    • Corticotrophin-releasing hormone, released during starvation
      • Promotes appetite suppression
      • Also increases cortisol levels, which in turn increases the risk for osteoporosis
    • Vasopressin is high and oxytocin low in cerebrospinal fluid
      • Hypothesised to promote the unhealthy thought patterns
Investigations
  • FBC
    • normocytic normochromic anaemia
    • mild leukopenia
    • thrombocytopenia
  • Serum chemistry
    • metabolic alkalosis and hypokalaemia (vomiting)
    • metabolic acidosis, hyponatraemia and hypokalaemia (laxatives)
    • hypomagnesaemia
    • hypophosphataemia
    • hypocalcaemia
    • hypoglycaemia
    • elevated urea levels
  • TFTs
    • T3 low, T4 normal, TSH normal
  • LFTs
    • elevated ALT
    • elevated AST
    • decreased ALP
  • urinalysis
    • may show ketonuria
  • urine pregnancy test
    • to rule out pregnancy as cause for amenorrhoea
  • ECG
    • conduction defects
    • prolongation of QT interval
  • bone densitometry
    • osteopenia
    • osteoporosis
  • oestradiol (in females)
    • low levels
  • testosterone (in males)
    • low levels
Management

a) conservative
  • structured eating plan with oral nutrition
  • psychotherapy
    • behavioural family systems therapy
    • cognitive analytical therapy
    • conjoint family therapy
    • cognitive therapy
    • dietary counselling
    • educational behavioural therapy
    • ego-oriented individual therapy
    • focal analytical therapy
    • family therapy
    • interpersonal therapy
    • individual therapy
    • non-specific supportive clinical management
    • separated family therapy
b) medical
  • potassium repletion
  • oral, enteral or parenteral nutrition
  • fluid intake correction
  • magnesium repletion
  • calcium repletion
  • sodium repletion
  • selective serotonin reuptake inhibitors (SSRIs)
c) surgical

Prognosis
  • In those who are 9.1 to 13.6 kg underweight, weight gain averages between 0.9 and 1.4 kg a week
    • May require inpatient care for 2 to 3 months
  • Relapse rates are higher for patients discharged while underweight, putting inordinate pressure on families
  • Full remission can occur only when care continues as an outpatient
  • Patients who are treated early in adolescence and reside with their nuclear family have a good prognosis if treated by experienced personnel
    • About 70% of these patients have a full and lasting recovery
    • Time to recovery is 3 to 5 years
    • Older patients are prone to relapse
      • Considering AN in these patients as a chronic disease can promote a more effective management.
  • Long-term outcome
    • After 10 to 15 years of investigation, one study showed that over 75% of patients recovered completely
    • Study results showed 4 main predictors of negative long-term outcome:
      • sexual problems
      • impulsivity
      • protracted duration of anorexia
      • long inpatient treatment
  • Mortality remains high at 12%
    • Deaths are mainly due to suicide, or medical complications
    • Anorexia has the highest mortality among psychiatric diagnoses
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