Hypophosphataemia in anorexia nervosa.

The prevalence, causes, and consequences of hypophosphataemia in the clinical treatment of various diseases are described in the literature, but are not so seriously regarded as a severe electrolytical disturbance. The clinical conditions when hypophosphataemia should be suspected are listed in fig 1. There is a triad of disturbances: hypokalaemia, hypomagnesaemia, and hypophosphataemia which often follows trauma, and glucose overload. In anorexia nervosa patients, hypokalaemia, hypochloraemia, and metabolic alkalosis are commonly seen. A high prevalence of hypophosphataemia is seen among post-traumatic and/or critically ill patients undergoing intensive care. Infectious diseases are also associated with the risk of developing hypophosphataemia. Immunological disturbances can result from a deficiency of several nutrients, such as zinc. Hypophosphataemia was found in anorexia nervosa patients with respiratory distress and signs of pneumonia. Recently, it was reported that the main causes of death of patients with anorexia nervosa was electrolytic disturbance and infection. 14 The incidence of hypophosphataemia in a hospital population is usually associated with undernutrition followed by refeeding. Recent reports of hospital undernutrition should alert health and medical staV to the significance of low serum phosphate concentrations. For example, overambitious treatment of undernourished patients with high energy intake can cause hypophosphataemia related paralysis and respiratory insuYciency. Hypophosphataemia with symptoms of phosphate depletion was first described in connection with starvation during wartime and in prisoners when refeeding was initiated after a period of phosphate loss. 21 Milk (rich in phosphate) was a life saver. 22 Protein energy undernutrition predisposes to hypophosphataemia. 23 When a gradual breakdown of tissue takes place during starvation, total depletion of the body’s phosphate stores may develop, even though the serum phosphate level most often remains normal. Anorexia in adolescent girls occurs at a serum phosphate level of 0.8–1.0 mmol/l. Reference values vary with age. It has been stated that anorexia nervosa is a condition characterised by protein energy undernutrition, which may also explain other deficiencies said to exist in anorexia nervosa patients. Most deficiencies have a protein source, for example zinc, selenium, potassium, phosphate and calcium, in addition to vitamin D deficiency, due to low fat intake. These deficiencies may also contribute to loss of appetite. Anorexia, well described symptom in phosphate depletion and/or hypophosphataemia, has frequently been documented before other disturbances in both experimental and clinical conditions. Eight out of 10 case reports on the sequelae of hypophosphataemia in anorexia nervosa have described female patients. In one study, only two of 65 adolescents with anorexia nervosa were boys. Causes and consequences are both related to gender, the consequences of phosphate depletion diVering because of the smaller muscle mass of women than of men. Progressive hypercalciuria and negative calcium balance developed in women but not men. A smaller total phosphate pool in female rats has been found in experiments. Fatigue and muscle weakness, often reported in anorexia nervosa patients, may be an early hypophosphataemic sign of phosphate depletion, as is loss of appetite. 7 24 The dangerous consequences of phosphate depletion emphasise the urgency of this discussion (box 1). The fatal condition is connected with disturbed oxidative phosphorylation and adenosine triphosphate (ATP) depletion in almost all vital functions. Loss of appetite can predispose to major complications, such as growth disturbances, neurological sequelae, and demineralisation of the skeleton. Hypophosphataemia has been reported in anorexia nervosa patients in connection with neurological complications and both respiratory and congestive heart failure. Several case reports of hypophosphataemia in anorexia nervosa, in addition to the most Figure 1 Clinical conditions when hypophosphataemia should be suspected (PEM = protein energy malnutrition). Hypophosphataemia in addition to: