LEARN MORE...

Puberty

Content type

User Generated

Uploaded By

zngglnyrk

Pages

Showing Page:

1/4

PHYSIOLOGY OF PUBERTY

Endocrine control of puberty in males

• The testes secrete substantial amounts of testosterone in the 1

trimester of fetal

development and in the 1

few month of infancy.

• The testes then becomes dormant for the rest of infancy and

childhood

• From puberty to adulthood, reproductive functions is regulated by

hormonal links between the hypothalamus, pituitary gland and

gonads (the brain-testicular axis)

Endocrine controls of puberty in females

• Puberty is triggered by the same hypothalamic pituitary hormones

in girls as it is in boys

• Rising levels of GnRH stimulate the ant lobe of pituitary to secrete

FSH & LH

• FSH help develop the

ovarian follicles, which in

turn secrete estrogen,

progesterone, inhibin and a

small amount of androgen

• These hormone levels rise

gradually from ages 8 – 12

and more sharply early

teens

• Estrogens (estradiol, estriol

& estrone) are feminizing

hormones with widespread

effects on the body. Estradiol results in the most visible

changes.

Endocrine control of puberty

• The 1

demosratable biological change of puberty is the appearance of pulsatile LH release

during sleep

• As puberty progresses, the frequency and amplitude of LH peaks increase

• At the end of puberty, the difference b/t sleep & wake LH pattern disappear

• The LH surge is triggered by the increasing activity of neurons that release GnRH

• GnRH cause the ant pituitary to release gonadotrophins, LH & FSH

• The factor that cause the hypothalamus to start secreting GnRH/ the activation of the axis is

uncertain

• The precise trigger for the GnRH surge during puberty is not known

• The influence of adequate nutrition has long been known

• Hypothesis – when adequate body fat distribution has been attained (17% body fat for

female), a signal is sent to hypothalamus to trigger release of GnRH

• Leptin is probable hormone that trigger GnRH surges during early puberty

Showing Page:

2/4

• GPR54 gene appears to be critical for the normal development of puberty. It encodes a

protein that appears to have an effect on the secretion of GnRH by the hypothalamus

• Multiple factors are probably involved

Timing of onset of puberty

• The onset of puberty varies among individuals

• Puberty usually occurs

- In girls the ages of 10 and 14, while

- In boys it generally occurs later, b/t the ages of 12 and 16

• Adolescent girl’s reach puberty at earlier ages than were ever recorder previously. Nutritional

and other environmental influences may be responsible for this changes

Five phases in puberty

1. Adrenarche

• Adrenarche refers to a stage of maturation of the cortex of the human adrenal glands.

Increase in the secretion of adrenal androgens

• It typically occurs b/t ages 6 and 10 and involves both structural and functional changes

• Adrenarche is a process related to puberty but distinct from hypothalamic-pituitary-

gonadal maturation and function

2. Gonadarche

• It refers to the earliest gonadal changes of puberty. In response to pituitary

gonadotropins, the ovaries in girls and testes in boys begin to grow and increase the

production of the sex steroids, especially estradiol and testosterone

• In boys, testicular enlargement is the 1

physical sign of gonadarche, and usually of

puberty

• In girls, ovarian growth cannot be directly seen, so thelarche and growth are usually the

first evidence of gonadrche

3. Thelarche

• It is the first stage of secondary (postnatal) breast development, usually occurring at the

beginning of puberty in girls

• Thelarche is usually noticed as a firm, tender lump directly under the centre of the nipple

(papilla and areola)

• It is also referred to as a “breast bud”, or more formally as Tanner stage 2 development

• It may occur on one side first, or both sides simultaneously

4. Pubarche

• It refers to the 1

appearance of pubic hair in children

• Pubarche is one of the physical changes of puberty but should not be equated with it

since it may occur independently of complete puberty

• It usually result from rising level of androgens from the adrenal glands or testes but may

also result from exposure of a child to an anabolic steroids

5. Menarche

• It is the first menstrual period, or first menstrual bleeding in females

• It is considered the central even of female puberty, as it signals the possibility of fertility

• Timing of menarche is influenced by both genetic and environment factors, especially

nutritional status

Showing Page:

3/4

End of Preview - Want to read all 4 pages?

Access Now

Unformatted Attachment Preview

PHYSIOLOGY OF PUBERTY Endocrine control of puberty in males • The testes secrete substantial amounts of testosterone in the 1st trimester of fetal development and in the 1st few month of infancy. • The testes then becomes dormant for the rest of infancy and childhood • From puberty to adulthood, reproductive functions is regulated by hormonal links between the hypothalamus, pituitary gland and gonads (the brain-testicular axis) Endocrine controls of puberty in females • Puberty is triggered by the same hypothalamic pituitary hormones in girls as it is in boys • Rising levels of GnRH stimulate the ant lobe of pituitary to secrete FSH & LH • FSH help develop the ovarian follicles, which in turn secrete estrogen, progesterone, inhibin and a small amount of androgen • These hormone levels rise gradually from ages 8 – 12 and more sharply early teens • Estrogens (estradiol, estriol & estrone) are feminizing hormones with widespread effects on the body. Estradiol results in the most visible changes. Endocrine control of puberty • The 1st demosratable biological change of puberty is the appearance of pulsatile LH release during sleep • As puberty progresses, the frequ ...
Purchase document to see full attachment