Early puberty in boys is linked to a shorter lifespan and darker hair colour, according to the largest ever study of the genetics of male puberty, led by scientists at the University of Cambridge.

The study, published today in Nature Communications, identifies 76 regions of the genome that influence male puberty, several of which have previously been linked to obesity and body mass index (BMI), but including others linked to hair colour.

The timing of puberty varies widely between individuals and is thought to be determined by a broad range of environmental and genetic factors. Early puberty has been associated with higher risks for a range of later life diseases, including several cancers, cardiovascular disease and type 2 diabetes.

Most of our previous understanding of the role that genes play in puberty timing was based on studies in women, as the age of a girl’s first period is easier to remember than the milestones of puberty in boys, which include voice-breaking. A recent large-scale study of the DNA of 370,000 women identified 389 independent signals, accounting for approximately one quarter of the estimated heritability for puberty. In contrast, genetic studies of puberty timing in men are much fewer and smaller in scale.

Researchers at the MRC Epidemiology Unit at the University of Cambridge used data from more than 200,000 men of white European ancestry collected by the UK Biobank Study and 23andMe to study the role that genetics plays in male puberty. Men were asked about the timing of their voice breaking and when they first noticed facial hair.

Analyses of these data identified 76 regions of the genome associated with puberty timing in boys.

Co-first author Dr Felix Day from the MRC Epidemiology Unit said:

Many of the genetic effects we identified were associated puberty timing in both girls and boys, highlighting shared biological processes determining pubertal development between sexes. We did however also identify a number of genetic effects that uniquely influenced puberty timing in either boys or girls, but not in both, highlighting important genetic differences between sexes”

The team also found that boys who hit puberty relatively earlier than their peers were at a greater risk of poor health later in life, corresponding to nine months’ shorter life for each year earlier started puberty.

Dr Day commented:

The link between early puberty and shorter life expectancy may be partly explained by its negative impact on cardio-metabolic health and diseases such as Type 2 Diabetes. If so, then finding ways to prevent early puberty could help improve health in later life.”

Surprisingly, the team found three genetic variants associated with pubertal timing were located close to genes previously associated with hair colour. Further analysis showed that men with red, dark brown and black natural hair colours showed progressively higher odds of early puberty timing, relative to men with blond hair. Similarly, women with darker natural hair colours had earlier puberty timing relative to women with blond hair.

Senior author Dr John Perry, also at the MRC Epidemiology Unit said:

Our most surprising finding was that some of the genes that regulate puberty timing in boys and girls also determine hair colour, highlighting an interesting common set of hormonal regulators in the brain that regulate both of these seemingly diverse traits”

The research was largely funded by the Medical Research Council.

Reference

• Full paper: Ben Hollis, Felix R. Day, Alexander S. Busch, Deborah J Thompson, Ana Luiza G. Soares et al. Genomic analysis of male puberty timing highlights shared genetic basis with hair colour and lifespan. Nature Comms; 24 March 2020; DOI: 10.1038/s41467-020-14451-5