Women with the BRCA1 gene mutation may have a lower than normal number of eggs in their ovaries, new research indicates.
Germline mutations in the BRCA1 gene is an established risk factor for breast cancer and other types of cancer, say Professor Kelly-Anne Phillips of The University of Melbourne, Australia, and colleagues.
But "less is known about the non-cancer-related implications," they write in Human Reproduction.
The team point out that early findings suggest "ovarian reserve, and hence fertility, may be reduced in BRCA1 mutation carriers". "If confirmed, this could have clinical consequences for pregnancy planning, reproductive lifespan and perhaps ovarian function following chemotherapy," they add.
So they measured ovarian reserve, by testing levels of anti-Mullerian hormone, in 693 women on a breast cancer study. All were aged 25 to 45 years, with no personal history of cancer, and were not pregnant or breastfeeding.
Lower levels of anti-Mullerian hormone were significantly linked with BRCA1 mutations. The BRCA1 mutation group had a level 25% lower on average to the other women. BRCA2 mutations were not linked to levels of anti-Mullerian hormone. "This is consistent with other smaller studies in the literature," state the authors.
Professor Phillips said: "This means that women in their mid-30s, who carry the BRCA1 mutation, have, on average, ovarian reserves similar to those of non-carriers who are two years older.
"It’s important to remember that anti-Mullerian hormone is only one indicator of a woman’s potential fertility. Women with low levels can sometimes still have a baby and, conversely, women with high levels are sometimes unable to do so."
Phillips, K-A. et al. Anti-Müllerian hormone serum concentrations of women with germline BRCA1 or BRCA2 mutations. Human Reproduction 20 April 2016 doi: 10.1093/humrep/dew044
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