Melbourne: Women who carry a gene mutation linked to breast cancer risk may also have lower number of eggs in their ovaries, according to a new study. In the first large study looking at BRCA1 and BRCA2 genetic mutations and levels of anti-Mullerian hormone (AMH) in women who carry the mutated genes, researchers found that carrying the BRCA1 mutation was linked to AMH concentrations that were about 25 per cent lower than those in non-carriers. The effect was not seen in women with the BRCA2 mutation.
“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,” said Professor Kelly-Anne Phillips, from the Peter MacCallum Cancer Centre in Australia.
Although AMH is a reliable marker of ovarian reserve, it is only one indicator of a woman’s potential fertility. The ability to conceive and carry a baby to full term is affected by many other factors as well, Phillips said.
“Our findings suggest that women carrying the BRCA1 mutation should try to avoid delaying pregnancy until their late 30s or 40s when fertility is reduced anyway because of their age,” said Phillips.
Women who carry the BRCA1 and BRCA2 gene mutations have a higher risk of cancers in the breast, ovaries, fallopian tubes and peritoneum.
The risk increases with age and is generally higher for those with the BRCA1 mutation than with the BRCA2 mutation. The mutations are rare in the general population – about 0.1 per cent for BRCA1 and 0.2 per cent for BRCA2.
As mutation carriers enter their early 40s they are usually advised to have their ovaries and fallopian tubes removed in order to minimise their cancer risk.
For this reason, many women who know they are carriers try to have their children when they are younger. However, until now, there has been little good-quality evidence about the effects of these genetic mutations on non-cancer-related conditions such as fertility.
Researchers analysed AMH levels from 693 women, aged between 25-45 years (average age was 35), who had no personal history of cancer.
A total of 172 women were carriers and 216 women non-carriers from families carrying the BRCA1 mutations, and 147 carriers and 158 non-carriers were from families with the BRCA2 mutations.
The women retained both ovaries and were not pregnant or breast-feeding at the time that blood was taken from them. The researchers adjusted their results to take account of age, oral contraceptive use, body mass index and smoking.
The researchers said that their findings also raise the hypothesis that BRCA1 mutations carriers may have a higher than average risk of chemotherapy-induced menopause.
The study was published in the journal Human Reproduction.