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
Complain of bloating, abdominal pain, sore throat, and a feeling of fullness.
Often show poor concentration and poor self-esteem, not solely linked to weight gain or loss.
Weight loss with additional symptoms of heat intolerance, hyperactivity, polyuria, sweating, nausea with vomiting, diarrhoea, and tremors.
History of blurred vision, polyuria, polydipsia, and polyphagia are common with weight loss, but without purging.
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.
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.
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