Physical growth (particularly in males), and cognitive development can extend into the early twenties.Thus age provides only a rough marker of adolescence, and scholars have found it difficult to agree upon a precise definition of adolescence.The end of adolescence and the beginning of adulthood varies by country and by function.Furthermore, even within a single nation state or culture there can be different ages at which an individual is considered (chronologically and legally) mature enough for society to entrust them with certain privileges and responsibilities.
During their peak height velocity (the time of most rapid growth), adolescents grow at a growth rate nearly identical to that of a toddler—about 4 inches (10.3 cm) a year for males and 3.5 inches (9 cm) for females.
For example, researchers in neuroscience or bio-behavioral health might focus on pubertal changes in brain structure and its effects on cognition or social relations.
Sociologists interested in adolescence might focus on the acquisition of social roles (e.g., worker or romantic partner) and how this varies across cultures or social conditions.
The testes primarily release testosterone, and the ovaries predominantly dispense estrogen.
The production of these hormones increases gradually until sexual maturation is met.