Physiological Changes of Puberty Flashcards
What is puberty defined as?
Endocrine and gametogenic functions of the gonads develop
When does puberty start for boys / girls?
Girls: 8 to 13 years
Boys: 9 to 14
What is the “timing” of puberty?
How mature a child is relative to his/her peers at the same age and gender.
What is the “tempo” of puberty?
How quickly or slowly a child progresses throughout the stages of puberty to the complete development
How many stages of puberty are there?
5 stages
What are the factors controlling the onset of puberty?
Genetic factors
Environmental factors
What are the categories under environmental factors?
Nutritional
Geographical location
Exposure to light
When does adrenarche begin and what is its function?
Girls: 8 to 10 years
Boys: 10 to 12 years
To produce androgens
What causes thelarche and menarche?
The production of ovary hormones (oestrogen and progesterone)
What initiates puberty?
Maturation and reactivation of the HPG axis
What is the cycle of HPG axis?
Well-developed at birth
Remains suppressed during childhood
Reactivated at the onset of puberty
How does CNS control puberty?
Hypothalamus releases GnRH
Pituitary releases LH and FSH
Ovaries and testes which release testosterone, oestrogen and progesterone
First half of pregnancy HPG axis:
The surge in FSH and LH secretion is hypothalamus independent, gonadotropins release those hormones on their own.
When does FSH and LH secretion become hypothalamus dependent? Why?
2nd half of pregnancy
Inhibited by placenta hormones
FSH and LH levels during infancy?
They peak due to loss of negative feedback by placental hormones
Why is there a low level of GnRH during prepubertal years?
High sensitivity of the hypothalamic-pituitary system to negative feedback inhibition by low levels of gonadal steroids +/- CNS inhibitory mechanism
What is testosterone surge induced by in fetal age?
hCG
At the what age stage is testosterone induced by FSH and LH?
Infancy
What induces testosterone surge during puberty?
Pulsatile LH and FSH
What may cause the onset of puberty?
Diminished brain inhibition or neural stimulation of the hypothalamic “gonadostat”
What does the increase in GnRH secretion stimulate?
Pituitary gonadotropin secretion and gonadal sex steroid production.
What factors are included in the maturation process that triggers onset of puberty?
Kisspeptin and Gamma-aminobutyric acid.
What is kisspeptin and what is its function?
It is a peptide hormone that is secreted by the hypothalamic neurone and potently stimulates the release of GnRH
What is GABA and what is its function?
A neurotransmitter that appears to play an important role in the inhibition of GnRH. A decrease in GABA could play a role in the onset of puberty.
What is leptin?
A satiety-producing hormone secreted by adipocytes
How does a decrease in hypothalamic NPY happen?
Increase in leptin
What kind of signal does leptin provide the hypothalamus with?
Signal that informs there are sufficient energy stores to support reproduction.
Why do young women with anorexia stop menstruating?
There is insufficient fat and decrease in leptin so not sufficient energy stores to support reproduction
What is Tanner’s staging in girls?
5 stages of breast development and pubic hair growth
What is the first sign of puberty for girls?
Thelarche
What is the first stage of tanner’s staging in girls?
Prepubertal: childhood no glandular breast tissue, elevation of breast papilla, no pubic hair.
What happens during the second stage of Tanner’s staging in girls?
Breast budding with elevation of breast and papilla (thelarche) Downy soft pubic hair.
What occurs between the second and third stages of Tanner’s staging for girls?
Growth spurt
When is there an enlargement of the breast and areola? What else occurs during that stage?
Stage 3, darker, coarser and curled hair develops
What happens during the fourth stage of Tanner’s staging for girls?
Projection of areola and papilla to form the double mound. More dense hair fills the pubic triangle and external genitalia.
What is the difference in hair growth between stages 4 and 5 according to Tanner’s for girls?
Pubic hair is only limited to external genitalia and pubic triangle in stage 4 while in stage 5 it spreads to inner thigh too
When does menarche occur?
Between stages 4 and 5
What happens in the final stage of Tanner’s staging for girls?
Matter breast, loss of double mound, dense air that extends beyond the inguinal area onto inner thigh.
Why is there a loss of the double mound of the breast during stage 5?
Due to the projection of the papilla only and the recession of the areola to the level of the breast.
What is a limitation of Tanner’s staging when it comes to boy’s pubertal development?
Does not include testicular volume which is the sign of initiate of puberty for boys.
What is the testicular volume required for puberty to start?
Greater than 3ml
What is the instrument used to measure volume and size of testes?
Prader orchidometer
What is stage 1 of Tanner’s staging for boys and what does it include?
Prepubertal: Childhood
Testicular volume <3ml and no pubic hair.
What is the second stage of Tanner’s staging for boys and what is its significance?
Enlargement of testicular volume, little or no change in penile size, downy soft pubic hair.
Initiation of puberty
What is the testicular volume in stage 1?
Between 3 to 6 ml
When is the testicular volume between 8 and 12ml?
Stage 3
What occurs in stage 3 of tanner’s staging for boys?
Testicular volume increases more, penile lengthening, darker, coarser and curled hair is developed.
When does growth spurt occur according to Tanner’s staging for boys?
Between stages 3 and 4
What occurs during stage 4 of Tanner’s staging for boys?
Testicular volume increases to 12 to 15, penile lengthening and broadening. Hair fills the pubic triangle and external genitalia.
What occurs during the fifth and final stage of Tanner’s staging for boys?
Testicular volume is over 15ml, adult genitalia, pubic hair extends beyond inguinal area onto inner thigh.
Why does growth stop eventually?
Growth plates of bones close, closure of epiphyseal plate
What causes the closure of epiphyseal plates?
Influence of oestrogen for girls and testosterone for boys
What happens to growth if puberty starts earlier than expected?
The height development will decrease because growth plates will close earlier
What happens if oestrogen and testosterone are absent but LH and FSH are present?
Development of secondary sexual characteristics but no gametogenesis.
What are the two types of precocious puberty?
True precocious puberty and pseudo-precocious puberty.
What is true precocious puberty?
Premature activation of the HPG axis, early gametogenesis and appearance of secondary sexual characteristics.
What is pseudo-precocious puberty?
Premature sex steroid secretion, primary disorder of the gonads or adrenal gland independent of hypothalamic-pituitary control
What occurs during pseudo-precocious puberty?
Early development of secondary sexual characteristics without gametogenesis.
What is considered a delay in puberty for boys?
Testicular volume < 3ml by the age of 14
What is considered a delay in puberty for girls?
Lack of thelarche by 13, or menarche by 15.
What are the two types of delayed puberty?
Pubertal delay, pubertal failure
What is the diagnosis for pubertal failure?
Turner’s syndrome
Why do boys often develop gynecomastia during the first stages of pubertal development?
Imbalance between oestrogen and testosterone, abnormal sensitivity of the mammary glands to oestrogen, exaggerated conversion of testosterone to oestrogen.
When is gynecomastia considered normal and when not?
If it during stages 2, 3, or 4 of pubertal development then it is normal and resolves within 6 months to 2 years. If it stage 5, it is always pathologic
