Boys today may be on a faster track to puberty than their fathers' generation, reaching the milestone an average of a year earlier, hints a large new study.
"Studies done several decades ago in the same population reported that a leap forward in sexual development occurs at ages 13 through 16," researcher Dr Fnu Deepinder of Cedars Sinai Medical Centre, in Los Angeles, told. "However, our study indicated that this spurt takes place between 12 and 15 years old."
The new finding suggests that the trend towards earlier puberty isn't limited to girls, who had already been shown to be developing sexually at increasingly younger ages.
Penis length and circumference measured
In the study, 6,200 healthy Bulgarian boys between 0 and 19 years old underwent measurements of height, weight, testicular volume, penis length and circumference.
Deepinder and his colleagues found that boys' testicles did not grow substantially until the beginning of puberty, around age 11. Penises, on the other hand, appeared to grow gradually from birth to sexual maturity - starting at around 2 inches (5 centimetres) and reaching an average length of nearly 9.5 centimeters by the age of 19.
However, both penises and testicles grew most rapidly between ages 12 to 16, the researchers report in the Archives of Paediatrics and Adolescent Medicine.
Boys also added the most inches in height and put on the most pounds between 12 and 14 years old.
Men not more well-endowed today
While boys of the same age in a 1970s study - also conducted in Bulgaria - had relatively smaller genitalia, men are not necessarily more well-endowed today. The size differences disappeared by the age of 17.
Deepinder suggested that genetic, environmental, nutritional and educational factors could be behind an accelerated development among boys today, adding that it remains unclear whether specific differences exist between populations from different parts of the world.
Boys born in rural areas, according to the study, grew slightly longer penises than their urban peers, although the difference was only about a sixth of an inch (about 0.4 cm).
No long-term dangers for girls
The researchers also don't make any guesses as to what this accelerated trajectory may mean for men's health. However, there is some evidence that earlier puberty holds few long-term dangers for girls.
Deepinder and his team point to an ongoing lack of general agreement over the "normal" size of a penis or testicle during the growing years, which can prove problematic given the large number of doctor visits concerning such measures.
"We have provided a table for height, weight, testicular volume and penile length and circumference of boys aged 0 to 19 years, which can serve as a useful reference source for physicians in diverse clinical practices," Deepinder said.(Reuters Health/ November 2010)