Pathophysiology
P-II-3. Gastrointestinal disease, Case 3
消化管疾患 症例3
A 17-year-old girl visits her GP at the urging of her parents. Her mother is distressed by her significant weight loss. The patient says that her mother is overreacting the situation; and she feels well, sleeps well, although her mood is not the best and she has not had her period for several months. Her appetite has decreased but she eats when she is hungry. She says she is not happy with her weight and would like to lose a few more kilos. She has been dancing ballet for years and exercises several hours a day. She feels that her relationship with her mother is strained and that she wants to control her in everything. On physical examination, the patient is 173 cm tall and weighs 46.7 kg.
Key Quotes & What They Tell Us
| Quote / Value | Interpretation |
|---|---|
| 173 cm, 46.7 kg (BMI ≈ 15.6) | Significantly underweight → meets the low-weight criterion for anorexia nervosa |
| “not happy with her weight and would like to lose a few more kilos” | Distorted body image and intense drive for thinness despite being underweight |
| “her mother is overreacting … she feels well” | Lack of insight / denial of illness severity |
| “not had her period for several months” | Amenorrhoea from hypothalamic suppression due to low body weight/energy |
| “dancing ballet for years and exercises several hours a day” | Excessive exercise — a compensatory weight-control behaviour |
| “relationship with her mother is strained … wants to control her” | Control/autonomy conflicts frequently associated with the disorder |
Key Points
- Diagnosis: Anorexia nervosa (restrictive type).
- Core features: Significantly low body weight, intense fear of weight gain / distorted body image, and behaviours (restriction, excessive exercise) to maintain low weight.
- Endocrine consequence: Hypothalamic amenorrhoea from low energy availability.
- Psychological aspects: Poor insight/denial and family-control dynamics.
- Pathophysiology: Chronic energy deficit → multisystem effects (menstrual, metabolic, cardiovascular) and risk of refeeding complications if rapidly re-fed.
一問一答
▶What are the core diagnostic features of anorexia nervosa?
Significantly low body weight, intense fear of weight gain / distorted body image, and behaviours (restriction, excessive exercise) to maintain low weight.
▶What is the diagnosis in a 17-year-old ballet dancer with BMI ~15.6, amenorrhoea, and a desire to lose more weight?
Anorexia nervosa (restrictive type).
▶Why does the patient develop amenorrhoea?
Low body weight and energy availability suppress the hypothalamus, causing hypothalamic amenorrhoea.
▶What does the patient's wish to 'lose a few more kilos' despite being underweight indicate?
A distorted body image and intense drive for thinness, characteristic of anorexia nervosa.
▶How is BMI calculated, and what is the patient's BMI (173 cm, 46.7 kg)?
BMI = weight(kg)/height(m)² ≈ 46.7/1.73² ≈ 15.6 kg/m², which is significantly underweight.
▶What does the patient's insistence that 'her mother is overreacting' and that she feels well reflect?
Lack of insight / denial of illness severity, common in anorexia nervosa.
▶How does several hours of daily ballet/exercise fit the picture of anorexia nervosa?
Excessive exercise is a compensatory weight-control behaviour driving the energy deficit.
▶What family/psychological dynamic is frequently associated with anorexia nervosa?
Control and autonomy conflicts, such as the strained, controlling relationship with her mother.
▶What is the underlying pathophysiology driving the multisystem effects of anorexia nervosa?
A chronic energy deficit producing menstrual, metabolic, and cardiovascular consequences.
▶What dangerous complication can occur if a severely underweight patient is re-fed too rapidly?
Refeeding syndrome (refeeding complications) from rapid metabolic/electrolyte shifts.
▶Why might an anorexia nervosa patient still report feeling well despite serious illness?
Poor insight and denial mean the patient minimizes symptoms even when objectively unwell.
▶How does the restrictive type of anorexia nervosa maintain low weight?
Through dietary restriction and excessive exercise rather than binge-purge behaviours.
▶What general body systems are affected by the chronic energy deficit of anorexia nervosa?
Menstrual (amenorrhoea), metabolic, and cardiovascular systems.
▶Why is amenorrhoea an important clinical clue in a young underweight woman?
It signals that low body weight has suppressed the reproductive (hypothalamic-pituitary-gonadal) axis.
▶Does decreased appetite mean the same thing in anorexia nervosa as in this patient?
The patient still eats when hungry; the disorder is driven mainly by deliberate restriction and drive for thinness, not loss of hunger.
▶What low-mood feature is described in this patient, and why does it matter?
Her mood is 'not the best' — depressive symptoms commonly accompany anorexia nervosa and affect management.
▶Which BMI value confirms the underweight criterion for anorexia nervosa in this case?
A BMI of about 15.6 kg/m², well below the 18.5 underweight threshold.
▶Why is family involvement both a clue and a challenge in adolescent anorexia nervosa?
Family control conflicts often feature in the illness, yet family support is also key to treatment.
▶What distinguishes a distorted body image from simply wanting to be thinner?
In anorexia the patient perceives herself as needing to lose weight despite being objectively, dangerously underweight.
▶What overall principle links the weight loss, amenorrhoea, and mood symptoms in this case?
All stem from a sustained energy deficit produced by restriction and over-exercise in anorexia nervosa.