Eating Disorders

Anorexia

Anorexia nervosa is an eating disorder characterized by restriction of food intake due to a fear of gaining weight and disturbance of one's perception of one's body. It may be divided into 2 subtypes:

• Restrictive: Severe limitation of food intake is the primary means to weight loss.

• Binge-eating/purging: Periods of food intake are compensated by self-induced vomiting, laxative or diuretic abuse, and/or excessive exercise.

Patients with anorexia are commonly known to be "perfectionists". Suspect anorexia if a question stem describes a young patient who is extremely competitive and high-achieving with a low BMI (particularly BMI < 18.5).

Treatment of anorexia involves psychotherapy. Consider addressing maladaptive family dynamics leading to feelings of inadequacy in the patient, as these life stressors could exacerbate the condition. Hospitalization may be necessary in cases of crisis, whether medical (arrhythmia) or psychiatric (suicide).

SSRIs are not typically effective due to lack of tryptophan from nutritional deprivation (contrast this to the treatment of bulimia nervosa!).

Avoid bupropion for comorbid depression in anorexia, due to the drug's low seizure threshold. The common electrolye imbalances in anorexia put patients at higher risk for seizures.

Low-dose atypical antipsychotics such as olanzapine may be used to promote weight gain in anorexia. Other sedative psychoactive medications such as mirtazapine may have a role as well.

Note that such pharmacotherapy has no value in bulimics, who typically have normal or above normal body weight.

Anorexia nervosa most commonly coexists with depression.

The most common cause of death in anorexia is heart disease. Suicide and starvation are also possible causes.

Anorexia is uniquely associated with a number of medical complications, mostly derived from the central pathological event of starvation.

Anorexia nervosa is associated with severe weight loss, metatarsal fractures, amenorrhea, anemia, and electrolyte disturbances.

Nutrient deprivation in anorexia can lead to early-onset osteoporosis.

Anorexic patients may develop elevated cholesterol.

Patients with anorexia have at-risk pregnancies: IUGR, prematurity, and smallness for gestational age.

Bulimia

Bulimia nervosa is characterized by binge eating followed by compensatory behavior such as vomiting or excessive exercise. There are two subcategories of bulimia, depending on the type of compensatory behavior utilized:

• Purging type: Involves vomiting, laxatives, diuretics, etc.

• Nonpurging type: Involves excessive exercise or fasting

In contrast to patients with anorexia, patients with bulimia are normal weight or slightly overweight (BMI >18.5 kg/m2).

Signs of bulimia may include hypotension, tachycardia, dry skin, and menstrual irregularities.

The 1st line pharmacological treatment for bulimia nervosa is a SSRI (e.g. fluoxetine). Psychotherapy is also useful.

Bupropion is contraindicated in patients with anorexia or bulimia since it can cause seizures in this population.

Binge- eating disorder

Binge-eating disorder is characterized by episodes of overeating without compensatory behavior. It is essentially an eating disorder that does not fit the qualifications of bulimia nervosa, due to lack of compensatory vomiting or exercising.

Treatment of binge-eating disorder centers around psychotherapy.

Signs of bulimia may include hypotension, tachycardia, dry skin, and menstrual irregularities.

Repeated vomiting

There are several complications of repeated vomiting in patients with eating disorders. Note that these can be seen in both anorexia and bulimia, depending on what subtype of each eating disorder the patient has.

Esophageal tears (Mallory-Weiss syndrome) and rupture (Boerhaave syndrome) can be found on endoscopy in patients with repeated vomiting.

Dental caries and parotid gland hypertrophy (with elevated amylase) can be a sign of vomiting.

Dorsal hand calluses (Russell's sign) can form from induced vomiting.

Euthyroid Sick Syndrome

Euthyroid sick syndrome is a spurious thyroid function abnormality seen in anorexia nervosa (and other chronic systemic illnesses). Starvation in anorexia can decrease thyroid-binding globulin levels and produce a picture of euthyroid hypothyroxinemia. This becomes relevant because anorexic patients can have symptoms similar to hypothyroidism (e.g. hair loss, fatigue, cold sensitivity, etc.), while simultaneously having misleadingly low thyroxine levels due to euthyroid sick syndrome.

Thyroid function test findings in euthyroid sick syndrome are differentiated from true hypothyroidism by a pattern of low T3 and/or T4, but normal or slightly decreased TSH (contrasted to the elevated TSH in true hypothyroidism).

• Critically ill patient will have low TSH and low T3/T4 that looks like central hypothyroidism

• rT3 rises in critical illness due to impaired clearance

Checking rT3 in critically ill patient will tell whether patient has central hypothyroidism or sick euthyroid syndrome.

Refeeding Syndrome

Refeeding syndrome may occur in anorexia nervosa when significant amounts of food are suddenly introduced into the diet of a patient who has been starving. It is caused by a sudden surge of insulin which causes electrolyte imbalances by shifting electrolytes intracellularly. Arrhythmias, respiratory failure, delirium, and seizures may occur.

The classic electrolyte abnormality observed is hypophosphatemia.