The age at which boys experience secondary sexual development for the second time

Early puberty: secondary sexual characteristics begin to appear until girls have menarche, and boys experience frequent nocturnal emissions for the first time. The main manifestation is a significant increase in physical growth and development, at about 9-13 years old.

Mid to late adolescence: This stage is characterized primarily by the development of reproductive organs and secondary sexual characteristics. It begins when girls experience their first menstrual period and boys start experiencing frequent nocturnal emissions, and continues until these secondary sexual characteristics are fully developed. They are approximately between 13 and 16 years old.

Late stage of puberty: From the time when secondary sexual characteristics begin to develop fully until reproductive function is fully established and growth in height stops, girls start to experience regular menstrual cycles, typically between the ages of 16 and 18.

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Slow onset of puberty

The delay in puberty falls within 2 to 2.5 standard deviations of the normal age distribution for the respective ethnic groups. It generally refers to the situation where, in females, breast development does not occur by the age of 13, and in males, there are no signs of significant enlargement of the testes or any indications of the onset of secondary sexual characteristics by the age of 14

In addition to this, even if the onset of puberty proceeds normally, any delay in its progression—such as a girl not experiencing her first menstrual period by the age of 16 or more than five years after the onset of puberty, or a boy not completing the development of secondary sexual characteristics more than five years after the onset of puberty—is also considered a delay in puberty.

If a boy or girl's growth and development occurs 1 year earlier or later than average, it is generally considered normal. However, if it differs by 2 years, it is advisable to consult a doctor and take the situation seriously; intervention may be necessary in some cases. A difference of 3 years indicates potential abnormalities in puberty, and medical intervention is usually required. In general, precocious puberty is more common in girls, while delayed puberty and growth are more frequently observed in boys.