Period when the endocrine and gametogenic functions of the gonads have first developed to the point where reproduction is possible
This is characterized by sequence of events by which a child becomes a young adult;
- The beginning of gametogenesis
- Secretion of gonadal hormones
- Development of secondary sexual characters and reproductive functions
- Sexual dimorphism is accentuated.
Factors affecting the onset of puberty
The age of onset of puberty varies and is more closely correlated with osseous maturation than with chronological age
- Genetic/Ethnic factors
- Environmental/Geographical factors
Prepubertal stage (8–9 yr of age)
The hypothalamic-anterior pituitary-gonadal axis is suppressed by;
- Neuronal restraint pathways
- Negative feedback provided by minute amounts of circulating gonadal steroids
Thus there are undetectable serum levels of;
- luteinizing hormone (LH)
- sex hormones (i.e., estradiol in girls, testosterone in boys)
Evidence of hypothalamic-anterior pituitary-gonadal interaction during the prepubertal period resides in the fact that serum follicle-stimulating hormone (FSH) concentrations are detectable in most children and may be increased (with serum LH concentrations) in;
Peripubertal period (1-3 yr before the onset of puberty)
Pulsatile secretion of low levels of LH during sleep secondary to endogenous episodic discharge of hypothalamic gonadotropin-releasing hormone (GnRH). Nocturnal pulses of LH continue to increase in amplitude and, to a lesser extent, in frequency as clinical puberty approaches. Serum LH concentrations rise earlier in the course of the pubertal process in boys than in girls.
This pulsatile secretion of gonadotropins is responsible for;
- Enlargement and maturation of the gonads
- The secretion of sex hormones
- Appearance of the secondary sex characteristics
GnRH is the major, if not the only, hormone responsible for the onset and progression of puberty.
A second critical event occurs in middle or late adolescence in girls, in whom cyclicity and ovulation occur. A positive-feedback mechanism develops whereby rising levels of estrogen in midcycle cause a distinct increase of LH.
Puberty in Girls (8-13yr)
- Thelarche (Development of Breasts) – Breast bud – 10–11 yrs
- Pubarche (Development of axillary and pubic hair) -Appearance of pubic hair – 6–12 mo later
- Peak height velocity occurs early (at breast stage II–III, typically between 11 and 12 yr of age) in girls and always precedes menarche.
- Menarche (first menstrual period) Interval to menarche – 2–2.5 yr but may be as long as 6 yr after thelarche. Mean age of menarche – 12.75 yr. (13.5 yrs in rural girls)
Puberty in Boys (9-14yr)
- Growth of the testes (>3 mL in volume or 2.5 cm in longest diameter)
- Thinning of the scrotum
- Pigmentation of the scrotum
- Growth of the penis, seminal vesicles and prostrate
- Pubic hair then appears
- Appearance of axillary hair usually occurs in midpuberty, 2 yr after pubic hair.
- In boys, unlike girls, acceleration of growth (5-15cm/yr in early adolescence but later drops) begins after puberty is well under way and is maximal at genital stage IV–V (typically between 13 and 14 yr of age).
- In boys, the growth spurt occurs approximately 2 yr later than in girls, and growth may continue beyond 18 yr of age.
Adrenal cortical androgens also play a role in pubertal maturation.
Serum levels of dehydroepiandrosterone (DHEA) and its sulfate (DHEAS) begin to rise at approximately 6–8 yr of age, before any increase in LH or sex hormones and before the earliest physical changes of puberty are apparent.
DHEAS is the most abundant adrenal C-19 steroid in the blood, and its serum concentration remains fairly stable over 24 hr; a single measurement of this hormone is commonly used as a marker of adrenal androgen secretion.
Although adrenarche typically antedates the onset of gonadal activity (i.e., gonadarche) by a few years, the two processes do not seem to be causally related, because adrenarche and gonadarche are dissociated in conditions such as;
- Central precocious puberty
- Adrenocortical failure
The period of life beginning with puberty and ending with completed growth and physical maturity.
Between the ages of 10 – 19 yr (WHO), children undergo rapid changes in;
- Phenotypic changes – Body size and shape
- Neuroendocrine changes – Hormones set the developmental agenda in conjunction with social structures designed to foster the transition from childhood to adulthood.
- Psychological functioning
- Social functioning
10-24 yr – Young Adults
Marshall – Tanner Classification of Sex Maturity Stages in Girls
Sparse, lightly pigmented, straight, medial border of labia
Darker, beginning to curl, increased amount
Coarse, curly, abundant but amount less than in adult
Adult feminine triangle, spread to medial surface of thighs
Breast and papilla elevated as small mound; areolar diameter increased
Breast and areola enlarged, no contour separation
Areola and papilla form secondary mound
Mature; nipple projects, areola part of general breast contour
SMR = sexual maturity rating.
Marshall – Tanner Classification of Sex Maturity Stages in Boys
Scanty, long, slightly pigmented
Darker, starts to curl, small amount
Resembles adult type, but less in quantity; coarse, curly
Adult distribution, spread to medial surface of thighs
Larger; glans and breadth increase in size
Enlarged scrotum, pink texture altered
Larger, scrotum dark
SMR = sexual maturity rating.
Developmental lines occur within three periods of adolescence;
Central Issues in Early, Middle, and Late Adolescence
||17–20 and beyond
||Secondary sex characteristics; beginning of rapid growth; awkward
||Height growth peaks; body shape and composition change; acne and odor; menarche; spermarche
||Sexual interest usually exceeds sexual activity
||Sexual drive surges; experimentation; questions of sexual orientation
||Consolidation of sexual identity
|Cognitive and moral
||Concrete operations; conventional morality
||Emergence of abstract thought; questioning mores; self–centered
||Preoccupation with changing body; self–conscious
||Concern with attractiveness, increasing introspection
||Relatively stable body image
||Bids for increased independence; ambivalence
||Continued struggle for acceptance of greater autonomy
||Practical independence; family remains secure base
||Same–sex groups; conformity; cliques
||Dating; peer groups less important
||Intimacy; possibly commitment
|Relationship to society
||Gauging skills and opportunities
||Career decisions (e.g., dropout, college, work)
SMR = sexual maturity rating.