NEW YORK (Reuters Health) - Levels of the male sex hormone testosterone in infant boys who are conceived using an assisted fertility technique called intracytoplasmic sperm injection (ICSI) are significantly lower than in their naturally conceived counterparts, according to Danish researchers.

ICSI is the main method used to overcome male infertility. With ICSI, a single sperm is injected directly into a single egg. If successful fertilization occurs, the embryo is then placed into the female to undergo development as usual.

There has been concern for the health of children conceived by assisted reproduction technologies, Dr. Anders Juul and colleagues at Copenhagen University Hospital note in their study, published in the Journal of Clinical Endocrinology and Metabolism.

The researchers investigated whether the impaired testicular function of the father might be inherited by boys conceived by ICSI.

The study involved 125 boys conceived by ICSI, 120 conceived by in vitro fertilization, sometimes called "test tube" fertilization, and 933 naturally conceived boys. Standard growth measurements were taken at birth and at 3 months, and blood samples were also taken from more than half of the infants at 3 months.

The team found that testosterone levels in the blood were reduced in boys conceived by ICSI compared with the naturally conceived boys. Boys conceived by in vitro fertilization, which is performed because of female infertility, also had normal testosterone levels.

Juul and colleagues believe that these findings suggest an inherited impairment of testosterone-producing cells in ICSI-conceived boys.

The possible repercussions of these findings still need to be investigated, the investigators conclude. However, they point out that the findings are of concern "because ICSI is increasingly used to overcome male infertility."

SOURCE: Journal of Clinical Endocrinology and Metabolism, July 2007.

REUTERS