Anorexia nervosa

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Anorexia nervosa

Psychological disorders

Bipolar and related disorders

Bipolar disorder

Feeding and eating disorders

Anorexia nervosa

Bulimia nervosa

Medication-induced movement disorders and other adverse effects of medication

Neuroleptic malignant syndrome

Serotonin syndrome

Somatic symptom and related disorders

Factitious disorder

Somatic symptom disorder

Trauma and stressor-related disorders; Abuse

Physical and sexual abuse

Post-traumatic stress disorder


Anorexia nervosa


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USMLE® Step 1 questions

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High Yield Notes

3 pages


Anorexia nervosa

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USMLE® Step 1 style questions USMLE

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A 17-year-old girl is admitted to the hospital for nutritional support after her parents brought her to the hospital earlier today due to marked dehydration and weakness. The patient has a past medical history significant for anorexia nervosa which was being treated with psychotherapy. On admission, the patient’s temperature is 36.4°C (97.5°F), pulse is 52/min, and blood pressure is 84/62 mmHg. Body mass index is 15 kg/m2. Parenteral nutritional replenishment is started. On the second day of admission, the patient is experiencing severe myalgias, paresthesias, and shortness of breath. Physical examination reveals bibasilar crackles. Laboratory evaluation reveals markedly decreased serum potassium levels and phosphorus levels. Increased secretion of which of the following hormones is most likely the cause of this patient’s current clinical condition? 

External References

First Aid








Anorexia nervosa p. 590

anovulation with p. 669

treatment p. 726

Mirtazapine p. 245, 600

anorexia nervosa p. 726


anorexia nervosa p. 726


Content Reviewers

Anorexia nervosa, which is often just called anorexia, is a disorder characterized by very low weight (typically less than 85% of normal body weight), a constant fixation on avoiding putting on even the slightest amount of weight, and having a distorted view of one’s own body weight or shape, often believing that one is overweight, while actually being underweight.

There are two main types of anorexia. One form of the disorder is the restricting type, where people reduce the amount of food they eat in order to lose weight.

Another form of the disorder is the binge-and-purge type, where individuals eat large amounts of food in one sitting and then purge that food by vomiting or taking laxatives.

This second type can be confused with another eating disorder, bulimia nervosa, but the main distinction between these two disorders has to do with an individual’s weight.

Individuals with bulimia are usually normal weight or overweight, whereas individuals with anorexia are underweight.

Because of this, people can potentially start out with bulimia, and then develop anorexia over time.

Anorexia can be further split by levels of severity.

A body mass index (or BMI) between 18.5 and 24.9 is considered healthy.

People diagnosed with anorexia have a BMI below this threshold: a BMI between 17 and 18.5 is considered mildly anorexic, a BMI of 16-17 is considered moderately anorexic, a BMI of 15-16 is severely anorexic, and a BMI of less than 15 is considered extremely anorexic.

In addition to having a low BMI, individuals with anorexia are typically fearful of weight gain, and often have a psychological obsession with the caloric and fat content of food.

This leads to food-restrictive behaviors, purging, over-exercise, and frequent weight checks.

People with anorexia might perform specific food rituals, like cutting food into small pieces, or eating foods in a specific order.

They might refuse to ever eat in front of people, or cook elaborate meals for others, but then not eat themselves.

Anorexia literally starves the entire body and can cause a number physical changes affecting every body system, which can end up providing clues to the diagnosis.

There is often a loss of muscle tissue throughout the body, reflected by a low creatinine level and symptoms of fatigue from weak muscles throughout the body, including a weak diaphragm which can cause difficulty breathing.


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