Attention, friends who menstruate: your DNA may be intervening in the length of your monthly cycle.

Although the average menstrual cycle is 27-30 days, each person's cycle is a little different. As you may know from biology class, the menstrual cycle is complicated. It is regulated by hormones such as estrogen, progesterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) that interact with each other through positive and negative feedback loops. Previous research has shown the importance of genes such as the FSHB gene (which codes for part of FSH) in this process: their levels of expression can cause all sorts of reproductive health problems, such as irregular periods.

Without going into the nitty gritty of how it all works, let's look a little more closely at how genetic factors affect the menstrual cycle length. In a genome-wide association study of more than 40,000 women, Laisk and colleagues found five statistically significant loci associated with menstrual cycle length. The five loci were located near five different genes, some which are known to play instrumental roles in menstrual cycle regulation (FSHB, PGR, and GNRH1) as well as newly discovered ones (IGF2 and NR5A2).

The IGF2 gene may be important because it stimulates the production of estrogen (which affects the regulation of other important menstruation-related hormones), which ultimately affects how follicles mature. As for NR5A2, the gene has been previously linked to age at menarche (or a person's first period). Interestingly, with respect to this gene, those with a specific variant were found to have longer menstrual cycles and tend to be older when they have their first period. If you're keen to learn more, check out the full study:

Unfortunately, the study is limited in that information on the length of menstrual cycles was entirely self-reported (which can be biased). Nevertheless, this study is still very useful because it is the largest genome-wide association study on menstrual cycle length so far. Future research using a more accurate way of measuring menstrual cycle length and with an even larger sample size would be fruitful.

If you menstruate, discover what your genes say about your monthly cycle length on Genomelink now!

Menstrual Cycle Length

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