14th February 2025

Anorexia nervosa

Presentation and diagnosis of anorexia nervosa

To make the diagnosis, a threshold of BMI <18.5 or rapid weight loss (>20% within 6 months) is used.

A typical pattern of behaviour prevents restoration of normal BMI: reduction of energy intake (restricted diet, purging with laxatives or vomiting, appetite suppressants) and increase in energy use (excessive physical activity). These features can be screened for using the SCOFF questionnaire.

Physical signs include sarcopaenia, dry skin, brittle hair and nails, Russell sign (thickened skin over the knuckles due to trauma from induced vomiting), hypothermia, pallor and swelling of the parotid and submandibular glands.

In order to investigate physical complications, the following investigations are recommended:

• FBC (anaemia, low platelets, leucopaenia)
• U&Es (raised urea, raised creatinine, low sodium and potassium)
• Bone profile (low phosphate and calcium)
• Magnesium (low)
• Bicarbonate (acidosis from laxative abuse or alkalosis from vomiting)
• LFTs (raised)
• Glucose (low)
• TFTs (low T3 and T4)
• ECG (sinus bradycardia, prolonged QTc, ischaemia, arrhythmia, complications of electrolyte derangement)

Physical illnesses such as brain tumours, Crohn’s and malabsorption disorders may mimic anorexia. Poor appetite may be caused by drugs, e.g. SSRIs. Depressive disorders or OCD can present similarly or may be concomitant.

Complications of anorexia nervosa

There is significant mortality; two thirds of cases due to physical complications, and one third suicide.

The physical health complications are widespread (Table 2). Cardiac complications are the most common cause of death, including bradycardia, hypotension, QT prolongation and cardiomyopathy. Amenorrhoea and infertility are seen in women due to hypothalamic dysfunction. Osteopaenia due to low progesterone and IGF-1 is common.

Table 2 Physical health complications of anorexia nervosa

Management of anorexia nervosa

Most cases are treated in the community with simple measures, including psychoeducation, monitoring of weight, involvement of family members, dietary counselling and eating disorder-focused CBT. Medication may be used as an adjunct, as per the individual’s psychopathology (e.g. an antidepressant for depressive symptoms).

Electrolytes should be closely monitored whilst restoring BMI, as the risk of refeeding syndrome is significant.

Admission to hospital may be required if outpatient treatment is unsuccessful, physical health complications pose a threat to life, there is severe or rapid weight loss, psychotic features are present, or if there is a high suicide risk.