Psychiatry and Mental Healthcommon
A 17-year-old girl is admitted for nutritional rehabilitation. She weighs 39 kg with a height of 168 cm, having lost 15 kg over six months through severe dietary restriction. Nasogastric feeding is commenced. On day 3 she develops generalised muscle weakness, swelling of both ankles and a pulse of 116/min. A fall in which one of the following serum electrolytes is the most likely cause of her deterioration?