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