Surreptitious metformin abuse in anorexia nervosa presenting as periodic hypoglycaemia

To the Editor

Anorexia nervosa is a severe form of mental illness with significant mortality and morbidity (Dawson et al., 2014). Laxative and diuretic abuses are commonly seen in anorexia nervosa. We report a rare case of anorexia nervosa with surreptitious metformin abuse.

A 21-year-old girl from an urban, extended joint family from Uttar Pradesh, India, was hospitalized for complaints of decreased food intake, weight loss and repeated vomiting for 8 years. She also had sadness of mood, crying spells, decreased interest in pleasurable activities and reduced sleep for 2 months. Before 8 years, she was overweight (body mass index [BMI] = 25.21 kg/m²) and was made fun of by her cousins. In pursuit of losing weight, she had restricted her food intake and used to induce vomiting secretly after consuming oily food. Despite significant weight loss over the initial 6 months, she continued with self-induced vomiting and dietary restrictions. Over the past 6 years, she developed constipation for which she self-medicated using ayurvedic remedies, the dose of which had gradually increased. Over the past year, she abused on a daily basis 500 mg metformin (an oral hypoglycaemic agent), which was prescribed for her elder brother who had non-insulin-dependent diabetes. In the last 6 months, she had multiple episodes of hypoglycaemic coma due to metformin overdose. She had amenorrhoea for the past 3 years.

During admission, her weight and height were 25 kg and 145 cm, respectively, with a body mass index of 11.89 kg/m². Her sub-mandibular and parotid glands were enlarged bilaterally.

Abdominal ultrasonogram had revealed cholelithiasis. Upper and lower gastro-intestinal endoscopy were within normal limits. Endocrinological evaluation revealed decreased follicle-stimulating hormone (FSH) and luteinizing hormone (LH) with normal thyroid profile. She was diagnosed with anorexia nervosa with major depressive disorder of moderate severity. She was started with mirtazapine 7.5 mg/day, which later was increased to 15 mg/day along with dietary scheduling. Cognitive behaviour therapy was administered, and she had shown improvement in her depressive symptoms and gained 5 kg weight in 3 months.

Peer influence during adolescence has a critical impact on body image perception, which may attribute to development of anorexia nervosa (Allison et al., 2014), which is also reflected in our case. Our patient had episodes of hypoglycaemia, which are common in patients with anorexia nervosa (Zalin and Lant, 1984) due to chronic starvation; however, the index patient’s hypoglycaemia was due to surreptitious abuse of metformin.