Puberty is an essential part of adolescent development. Some teens long for it, and some dread it, and most will experience both extremes in the intervening years. While puberty is different in boys and girls, some obvious signs can identify when a child has entered puberty. Identifying these signs can help parents and teens prepare themselves for the changes to come.

When Does Puberty Start?

Puberty occurs when a child's body begins to transition toward adulthood. The process typically starts between the ages of ten and 14 for girls and 12 and 16 for boys. Puberty lasts two to five years and entails growth spurts, new pubic and armpit hair, and, in some cases, acne. This latter issue occurs due to hormonal changes in both boys and girls and usually fades by the end of puberty.


Precocious Puberty

Precocious puberty occurs when physical and sexual development occurs too early in a child. This is very rare, even rarer in boys than in girls, and the cause is unknown. Some experts theorize a genetic cause, specifically a mutated MKRN3 gene. This mutation can also make individuals shorter and lead to behavioral and emotional problems.

Early Puberty Precocious Gene Mutation Imgorthand / Getty Images


Delayed Puberty

Delayed puberty is more common than precocious puberty and occurs when puberty begins later than expected. Most children and teens with this condition develop normally in the long run. Sometimes, low body mass and too little fat cause delayed puberty, but underlying chronic medical problems, eating disorders, and too much exercise can also have this effect. Some genetic disorders also cause delayed puberty.

Causes Delayed Puberty Normal Development imamember / Getty Images


Boys Gain Muscle Mass

When boys enter puberty, the physical changes that occur include the gaining of muscle mass. Many boys lose their "baby fat." Ultimately, slimmer boys will gain less muscle than their heavier counterparts, but a healthy diet and regular exercise can maintain normal development. Other physical changes in boys include a deepening voice and growth of facial hair and genitals.

Boys Physical Changes Puberty Muscle SolStock / Getty Images


Girls Both Gain and Lose Fat

Girls may gain weight as well, but not everywhere. The majority of their weight gain will occur in the lower abdomen, rear, thighs, and arms. Breast growth also contributes to increased weight. Girls may lose weight as well, in areas where the body deems storage unnecessary. Biologically, weight gain is preparing the body prepares for menstruation and childbearing, the extra weight protecting reproductive organs. During puberty, the hips and bottom also begin to round, and many girls experience growth spurts.

Girls Puberty Hormones Hips Breasts martin-dm / Getty Images


Increased Testosterone in Boys

Hormones are behind the deeper voice and various physical changes boys experience during puberty. Production of testosterone, primarily, begins to increase, assisting in the development of sperm and increasing sex drive. Testosterone levels peak in men in their 20s and gradually decrease as they age. Boys also begin to produce APB or androgen-binding protein during puberty.

Testosterone Boys Physical Changes Puberty theasis / Getty Images


Hormones and the Menstrual Cycle in Girls

Pubery in girls increases estrogen production, which often coincides with the beginning of the menstrual cycle. Usually starting late in puberty, at this time the body becomes capable of creating an egg and preparing it for fertilization, and releasing unfertilized eggs, on a set schedule. Estrogen also is responsible for changes in female anatomy and the growth of breasts and hips.

Menstrual Cycle Girls Estrogen Fertilization vgajic / Getty Images


Puberty Affects the Brain

Hormonal changes during puberty also affect the brain. There is some evidence that puberty is related to cognitive development, suggesting puberty may have an even greater effect on the brain than chronological age. During puberty and brain development, teenagers may experience mood swings and bouts of emotional instability while the brain matures.

Puberty Brain Hormones Age Changes stock-eye / Getty Images


Sexual Changes in Boys and Girls

Sex drive increases in both girls and boys during puberty. Boys may experience nocturnal emissions of semen or "wet dreams" as sperm levels in the testes increase. Girls may feel increased sex drive before and after their period. These hormonal changes differ in each child, and some may experience them more drastically than others. These feelings balance out with age as the hormones stabilize.

Puberty Sexual Drive Nocturnal Emissions ljubaphoto / Getty Images


Prepubescent Health Affects Puberty

The health of a child before puberty has a great deal to do with the beginning of puberty. Underweight, inactive, or ill children may experience complications due to substandard development. A diet high in processed foods can also affect the non-linear progress of puberty. One study observed the possibility of obesity delaying puberty in boys and causing precocious puberty in girls.

Prepubescent Health Processed Foods Obesity pixelfit / Getty Images


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