Beginning with the observation that children who are put up for adoption through international agencies are 80 times more likely to manifest precocious puberty than children who are brought up in their home country, the team of Professor Bourguignon has shown that DDT, an insecticide that is prohibited in this country, can cause precocious puberty, especially in the young daughters of migrants.

A tendency toward early puberty has been observed over the last several years in a number of European countries, including Sweden, France, Denmark, the Netherlands, Italy and Belgium. Several studies have pointed to the particularly high number of cases of precocious puberty among the children of migrants, including those who are put up for adoption through international agencies.

While working on the problem of infant growth as part of a group of pediatric endocrinologists brought together from the teaching hospitals of the country – the Belgian Study Group for Pediatric Endocrinology (BSGPE) – Professor Jean-Pierre Bourguignon, a pediatric endocrinologist from the University of Liège, began working on this problem as well. Working within the study group team, he suggested that a case registry be set up for children diagnosed with precocious puberty, a phenomenon that affects more girls than boys by a ratio of 10 to one. In general, the criteria for a diagnosis of precocious puberty agreed on by pediatric endocrinologists are as follows: the appearance of breast buds (thelarche) before the age of 8, and first menstruation (menarche) before 10 years of age. In the group of children studied, physicians observed that precocious puberty was brought on in three different ways: half of the cases had unknown or idiopathic causes; one quarter of the cases had organic causes (tumors, consequences of a case of meningitis, etc.); and one quarter of the cases involved the children of migrants, most of whom had been put up for adoption internationally. Several hypotheses were then formulated. There might have been causes related to ethnic origin, or to climate, or malnutrition, etc. But none of these hypotheses furnished a satisfying explanation, according to Professor Bourguignon. With regard to the migrant children, “it was calculated that the risk of appearance of precocious puberty was 80 times greater than that to which other children were exposed.”

At the Center for Cellular and Molecular Neurobiology (CNC) at the University of Liège and at the Pediatric Service of the CHU of Liège, to which Professor Bourguignon also belongs, two things set in motion a research effort toward the explanation of this phenomenon: on one hand, there was the realization that a large proportion of cases of precocious puberty involved the children of migrants. On the other hand, there were the conclusions of a much-discussed study by Marina Krstevska-Konstantinova (1) concerning the children of immigrants in Belgium who had been born on other continents.

Krstevska-Konstantinova is a researcher of Macedonian origin who came to work at the CHU in Liège thanks to a subsidy from the European Society of Pediatric Endocrinology. In 2001 for research revealed that some of the daughters of migrants developed breasts before the age of 8. Other studies had shown that girls put up for adoption through international agencies tended to menstruate much earlier than girls put up for adoption but born in this country, and also earlier than girls from other countries who were offered for adoption in their home countries. Krstevska-Konstantinova hypothesized that these children were being exposed to contaminants in Belgium to which they would not have been exposed in their home countries. The blood serum of these children revealed high levels of eight organochloride pesticides, as well as the presence of DDE, a chemical that is a byproduct of DDT, an organochloride insecticide that is widely banned but still used in the home countries of many of these migrant children.