Puberty

Puberty is a transitional stage between childhood and adulthood when secondary sexual changes occur, fertility is achieved and skeletal growth is completed. There are profound changes in an individual’s cognitive capabilities, self-concept and relationships with family, peers and society. Girls usually begin pubertal changes between ages nine to thirteen years, and boys typically begin puberty between ten and fourteen years.

The onset of puberty is controlled by the luteinizing hormone (LH), which is secreted by the pituitary gland. About one to three years prior to visible signs that an individual is entering puberty, the pituitary releases nocturnal pulses of LH. This hormone is responsible for the secretion of the sex hormones that include estrogen in females and testosterone in males. The interactions between LH, estrogens, testosterone and another pituitary hormone termed the follicle stimulation hormone (FSH) are mainly responsible for the appearance of the secondary sex characteristics. Other hormones involved in pubertal changes include progesterone in females and adrenal androgens in both males and females.

Ninety-nine percent of females in the United States will have at least one secondary sexual characteristic by age thirteen and ninety-nine percent of boys will have one characteristic by age fourteen years.

Secondary sexual characteristics in females:

• Breast development
• Public and axillary hair
• Increase in body fat mass
• Development of the labia, vagina, uterus and breast ducts
• Stimulation of skeletal growth

Secondary sexual characteristics in males:

• Enlargement of the testicles, penis, prostate, scrotum
• Pubic, axillary and facial hair
• Increase in muscle mass
• Increase in size of the larynx with deepening of the voice
• Acceleration of linear growth
• Stimulation of libido

Pubertal development follows a sequence in most, but not all, adolescents.

Sequence of Pubertal Events in Females

Sequence of Pubertal Events in Males

The sequence of pubertal events represents that of the average female or male. If a male begins puberty at age fourteen, then the sequence will take approximately five years to be completed. Menstruation usually occurs about two and one half years after the onset of puberty and this milestone is a signal that skeletal growth will end approximately one year later. Most adolescents will have achieved a particular pubertal milestone within the two years before or after the average age as noted in the tables.

Some adolescents have disordered pubertal development in that they either start puberty early or they have a delayed puberty. Early puberty, termed precocious puberty, can be caused by a variety of medical conditions, and it is important that clinicians be involved with medical evaluation of these individuals. Pubertal changes in girls before the age of eight years is precocious although approximately seven percent of Caucasian and twenty-seven percent of African-American girls may have breast development or pubic hair between ages seven and eight years. True precocious puberty in girls can be caused by problems in the central nervous system including brain tumors, head injury, brain radiation and neurofibromatosis. Other causes of precocious puberty include tumors of the ovary that secrete estrogens and androgenic hormones and disorders of the adrenal glands that produce estrogens.

Precocious puberty in males is defined as pubertal development before the age of nine years. Males may develop early due to organic brain disease including hydrocephalus, tumors or severe head injury. Males who develop adrenal or testicular tumors may also have an early puberty.

True precocious puberty should be evaluated. After the cause is found, then appropriate treatment may be prescribed to delay the onset of puberty.

Delayed puberty is defined as no signs of secondary sexual characteristics by age thirteen in girls and fourteen years in boys. Many adolescents who have a delayed onset of puberty have a family history where one parent was also delayed. Typically in these cases, the adolescent will start pubertal changes late, but will go through the changes including growth and development at a normal sequence and pace. For both males and females, one may have a delayed puberty if there is a central brain problem. This could include, for example, a pituitary lesion where LH or FSH cannot be synthesized. Cystic fibrosis, chronic renal disease, malnutrition and sickle cell disease are systemic diseases that may cause a delay in puberty.

Females who are delayed may have an ovarian problem. For example in Turner Syndrome which is a chromosomal disorder, the ovaries are poorly functioning remnants and cannot produce the required hormones for a girl to undergo pubertal changes and menstruation. Some males may have undescended testicles or some may not be able to synthesize adequate amounts of testosterone as may occur in Klinefelter’s syndrome which is also a chromosomal problem. In these cases, they may not undergo pubertal changes.

One of the most common causes of delay in the onset of puberty, especially in boys, is the constitutional delay. Usually the boy is healthy and there is a family history of late puberty. The boys will enter puberty later than average without any hormonal intervention. However, if a boy is particularly upset over his appearance, the physician may consider initiation of hormones to trigger the pubertal sequence.

After evaluation for delayed puberty, some adolescents may be started on hormonal therapy to initiate the pubertal sequence. For example, girls may be administered estrogens to start development, and then be cycled with estrogens and progesterone. And boys may be administered testosterone either through injection or administration of a patch to spark the pubertal process.

Although the first period, termed menarche, usually occurs around two and one half years after the first signs of pubertal development, fertility is not necessarily associated with that milestone. In fact, pregnancy probably cannot occur for at least one or two years after menarche. On the other hand, there are reports of individuals conceiving prior to their very first period.

Males do not have a visible milestone that may indicate fertility. In fact, production of sperm, termed spermarche, may actually begin when the first pubertal signs are visible. As puberty marches along in males, the sperm count increases and the chances of producing a conception will also increase.

Since the timing of fertility cannot be precisely defined, it is important that all adolescents be familiar with the concepts of family planning before the onset of puberty.

Related topics:

Breast development, chronic illness, erections and wet dreams, growth and development, Klinefelter’s syndrome, Turner syndrome