Johns Hopkins researchers have found that a variation in a gene involved in regulating cholesterol in the bloodstream may be responsible for infertility in women.
The altered gene has been found to be involved in both faulty cholesterol regulation and the production of pregnancy hormone, progesterone.
"Infertility is fairly common and a lot of the reasons for it are still unknown," warns Annabelle Rodriguez, endocrinologist, associate professor of medicine at the Johns Hopkins University School of Medicine.
"Right now, the benefit of this research is in knowing that there might be a genetic reason for why some women have difficulty getting pregnant. In the future, we hope this knowledge can be translated into a cure for this type of infertility," she added.
Researchers have developed a simple blood test for this variation of the scavenger receptor class B type 1 gene (SCARB1) but emphasized there is no approved therapy yet to address the problem in infertile women.
Following up studies in female mice that first linked a deficiency in these receptors for HDL, the so-called "good" or "healthy" cholesterol and infertility, researchers have reported finding the same link in studies of women with a history of infertility.
Between November 2007 and March 2010, researchers analysed ovarian cells and fluid collected from 274 women unable to become pregnant for various reasons and undergoing in vitro fertilization (IVF).
Some 207 of them went on to have their eggs collected, fertilized in a test tube and implanted in their wombs.
Researchers then measured whether there was evidence of a gestational sac or a fetal heartbeat 42 days after embryo transfer. They discovered that none of the nine women in the group had the mutated SCARB1, meaning none were pregnant.
According to Rodriguez, the genetic variation could be present in 8 to 13 pc of the population.
The study also showed that the nine women with the altered gene had low levels of progesterone, a hormone critical to sustaining pregnancy in its earliest stages. This is despite being supplemented with progesterone as part of the IVF process.
The study has been published online in the journal Human Reproduction.