In the 1700’s the average girl got her first period she was 16, 100 years later girls got their first period at age 14. Today, most girls start puberty at age 12.5, precocious puberty puts girls at risk for breast cancer, cardiovascular disease and type 2 diabetes later on in life. Additionally, girls who go through puberty earlier are more susceptible to low-self esteem and depression. The timing of puberty is determined by genetics but also mediated by nutritional and metabolic cues. Previous research has pointed to hormones in meat and chemicals in food as endocrine disruptors causing increased levels of estrogen earlier in development.
Estrogen Molecule-Wikimedia Commons
However, this October at Oregon’s Health and Science University, Alejandro Lomniczi explored the link between increased body weight and the early onset of puberty in female rats. The human genome has not changed drastically enough in the past 150 years to cause such a large change in the timing of puberty. Therefore, Lomniczi and his co-workers focused their research on epigenetics, a field of study that explores changes in gene expression rather than changes in the genetic code itself.
Overview of Puberty in Boys and Girls-Wikimedia Commons
In their study they raised overweight, average sized and lean female rats while searching for genes relating to the hypothalamus. The hypothalamus is found on the lower part of the brain and controls reproductive development and hormone release. Lomniczi found a puberty activating gene within the hypothalamus called Kiss1 that interacts with Sirtuin 1, an enzyme that transmits body weight information to the brain. Sirtuin 1 binds to the promoter of the Kiss1 gene inhibiting transcription and delaying puberty. In his study, Lomniczi found that overweight rats had less Sirtuin 1 in the hypothalamus which upregulated the Kiss1 gene causing female rats to go through puberty earlier than the lean and average weight rats. Average weight rats had higher levels of Sirtuin 1, delaying the expression of Kiss1 and the onset of puberty.
This epigenetic pathway makes sense evolutionarily, if the body senses extra fat and calories it believes that there is enough nutrient sources to support a baby, triggering reproductive maturation. Consequently, girls who are underweight or even anorexic experience delayed puberty or stop menstruating because of increased levels of Sirtuin 1.
With these established links between weight and precocious puberty the only thing parents can do to prevent this, is ensuring that children are receiving proper nutrition and daily exercise. Puberty in itself is an emotional time for both boys and girls, going through the process even earlier than their peers can have detrimental effects on on mental health and self-esteem.
-Priya Baichoo
