Male Infertility Could Signal Other Genetic Problems

Article excerpt

SAN ANTONIO -- Extremely low sperm counts are often caused by genetic defects that could pose other health risks to affected men and their potential offspring, Dolores Lamb, Ph.D., said at the annual meeting of the American Society for Reproductive Medicine.

"Normally in evolution, from a genetic standpoint, infertility is the end of the line. Nature has a built-in mechanism against passing along serious genetic defects to the next generation," explained Dr. Lamb, professor of urology and molecular and cellular biology at Baylor College of Medicine, Houston.

However, techniques that enable defective sperm to fertilize an egg--testicular sperm extraction and intracytoplasmic sperm injection (ICSI)--have made it possible for men to bypass that protective mechanism and father children, she said.

"Couples need to understand our level of ignorance. Because we don't understand all the genetic reasons behind male infertility, they need to know there may be other consequences beyond simply being infertile. Even with all the tests we can perform, there is no guarantee of a perfect baby," Dr. Lamb said in an interview.

Most studies suggest that there is no increased rate of birth defects among children conceived through ICSI, and chromosome problems in this population seem to be primarily restricted to the predicted sex chromosome abnormalities linked to male infertility. Still, some experts fear there may be undiscovered problems in children born from the sperm of severely azoospermic men.

"With chromosomal tests, it's like you are only looking at the outside of the 'Encyclopaedia Britannica.' You can say, 'Yes, we have an extra volume,' or 'We're missing a volume,' but you can't see if you're missing a chapter, which would be like missing a gene, or if you're missing a word, which would be like missing a portion of a gene. These microdeletions could potentially totally change or abolish the function of that protein." Dr. Lamb explained at the meeting.

She and her colleagues recently uncovered deficiencies in mismatch repair genes in some men with testicular failure, predominantly those with Sertoli-cell-only syndrome (Mol. …