Anorexia and bone mass

A multidisciplinary paediatrics research team has been awarded the “Amagoia” prize by the Sociedad Vasco-Navarra de Pediatría for its work, “Study of bone mass and its determinant factors in female children and adolescents affected by eating habit disorders”. The research was led by Dr. Cristina Azcona, responsible for the Paediatric Endocrinology Unit at the Department of paediatrics at the University Hospital in Navarre.

The patients affected by eating habit disorders are at greater risk from developing osteopenia and osteoporosis compared to the healthy population, mainly due to their state of malnutrition and hypogonadism. The aim of this research was to measure the bone mass in female children and adolescents with eating habit disorders by means of two techniques of measurement: bone densitometry (a technique also known as DEXA or Dual Energy X-ray Absorptiometry) and osteosonography.

The technique conventionally employed to assess bone mass is DEXA although, in recent years, the systems using ultrasounds (such as osteosonography) are being more frequently applied – especially amongst women during menopause. The use of osteosonography in child patients is not widespread as yet. Measurement systems applying this technique generally determine the bone mass in the calcaneum (the great bone of the heel) or the phalanges of the hand. This last system is the one that was used for this research.

It has the advantage of being portable, cheaper than DEXA and does not emit radiation, and so was thought particularly suitable for measuring bone mass in children and adolescents. The process of acquisition of bone mass starts at infancy and, during adolescence, the mineral content of the bone experiences a huge growth – compared to the rates at other stages of growth and child development.

From the perspective of primary prevention it is very important to have non-harmful methods at hand that evaluate bone mass in children given that, if the maximum bone mass is acquired during this period, the risk of suffering fractures during old age is reduced.

Conclusions

The research carried out at the University Hospital shows that, with both techniques for the measurement of bone mass, patients show values inferior to that of healthy children and adolescents. Comparing both techniques, it was observed that, paradoxically, osteosonography is a more suitable technique for the measurement of bone mass in those children and adolescents who have a body composition that is normal for their age, sex and puberal development. “It could be, nevertheless, a complementary method for monitoring the evolution of bone disorder in these patients and thus avoid tests that use radiation, although the DEXA continues to be the reference technique”.

Genetic involvement

The research also studied those determinant factors that may regulate the acquisition of bone mass. To this end, the Pediatrics Laboratory was the centre for the analysis of several polymorphisms of the vitamin D receptor genes, the collagen I-alfa-1 gene and the oestrogens receptor genes that are involved in determining bone mass.

The genetic markers for bone mass can help and identify patients who, because of their genetic make-up, are more prone to getting osteopenia and, in those cases of anorexia nerviosa thereby, may cause more severe complications in the osseous system.

Current treatments do not restore totally the lost bone mass and so, at least, one has to ensure an adequate ingestion of calcium and vitamin D from the outset of the illness.