1. Gonadotropin-releasing hormone (GnRH), also called luteinizing hormone-releasing
hormone (LHRH)
What hormones are attributed to
2. Luteinizing hormone (LH)
Hypothalamic-pituitary-GONADAL (HPG)
3. Follicle stimulating hormone (FSH)
axis?
4. Estrogen
5. Testosterone
What hormones are attributed to 1. Adrenocorticotropic hormone
Hypothalamic-pituitary-ADRENAL axis 2. Dehydroepiandrosterone (ACTH)
(HPA)? 3. DHEA sulfate (DHEA-S)
1. Growth hormone-releasing hormone (GHRH)
What hormones are attributed to Growth
2. Growth hormone (GH)
hormone (GH)?axis
3. Insulin-like growth factors (IGFs)
three distinct changes in the hypothalamic-pituitary unit:
(1) a nocturnal sleep-related augmentation of pulsatile LH secretion;
What is thought to be three distinct changes
(2) a decrease in the sensitivity of the hypothalamus and the pituitary to estradiol and
in the hypothalamic-pituitary unit that may
testosterone, so that the gonadotropins LH and FSH begin to increase; and
trigger puberty?
(3) in the female, development of a positive feedback system, whereby critical levels of
estrogen trigger a large release of GnRH, stimulating LH to initiate ovulation.
What scale allows for the accurate Sexual Maturity Rating (SMR) scale (also called the Tanner scale)
classification of physical pubertal maturation
1. Thelarche
Girls major events of puberty 2. Growth Spurt
3. Menarche
Often the earliest physical sign of puberty in girls, although a minority develop pubic
Thelarche hair as the first sign. On average, breast development starts at age 10.0 for Caucasian
girls and 8.9 years for African-American girls
Thelarche and pubarche (pubic hair) may both be preceded by about 1 year by the
Growth Spurt growth spurt; thus the growth curve is an essential tool in the evaluation of precocious
puberty.
This event usually occurs during SMR B3 or B4 and about 3.3 years after the growth
Menarche
spurt, or roughly 2 years after breast budding.
What is the average length of time for 4 years, but it can range from 1.5 to 8 years
completion of puberty ?
Testicular Growth: The first physical sign of puberty in the majority of boys is increased
What is the first physical sign of puberty in
testicular volume, although the most noticeable first event of male puberty is the
the majority of boys ?
growth of pubic hair
2. Growth Spurt: Midpuberty, or the time of rising testosterone concentrations, is
associated with the period of most rapid linear growth in boys, in contrast to the early
growth spurt in girls. It is also at this time that the voice changes axillary hair appears,
and possibly also acne. Facial hair growth typically starts about 3 years after pubic hair
What are other signs of male puberty? growth. The hair on the face, chest, back, and abdomen may continue to appear
throughout and beyond puberty into adulthood, its amount and distribution being quite
variable and dependent on ethnicity and family patterns.
3. Attainment of Fertility: Ejaculation usually occurs at SMR G3, as does the first
evidence of spermarche, but fertility is not usually attained until SMR G4.
, average length of time for the completion of puberty is 3 years, but it can range from 2
to 5 years.
What is the average length of time for Genital development is initiated at about 10.1 years for white boys, 9.5 years for African-
completion of puberty for boys? American boys, and 10.4 years for Mexican-American boys, with completion of puberty
at 15.9 years in white boys, 15.7 years in African-American boys, and 14.9 years in
Mexican-American boys.
The target tissues of LH and FSH are the ovaries and testes, which produce estradiol
Gonadal Steroids and testosterone, respectively. Testicular Leydig cells also produce androstenedione,
dihydrotestosterone, and estradiol, but to a much lesser extent.
Estradiol from the ovary accounts for the majority of the circulating estrogens, although
there is a small amount of extraovarian conversion from androstenedione and
Estrogen. testosterone. In addition to stimulating breast growth and maturation of the vaginal
mucosa, estrogen has been found to have a major impact on the skeleton, being the
primary hormone responsible for epiphyseal closure.
The testes produce most of the circulating testosterone, but a small amount comes
from extratesticular conversion of the adrenal hormone androstenedione in both males
Testosterone. and females. Testosterone is responsible for the voice change in males and the
attainment of male body habitus, while dihydrotestosterone, the product of conversion
of testosterone by 5a-reductase, causes growth of the phallus and prostate.
At the time of puberty, GnRH is secreted from the GnRH pulse generator in the
hypothalamus, leading to pituitary secretion of LH and FSH and subsequent secretion
of estradiol from the ovaries or testosterone from the testes. The exact triggers are still
GnRH Pulse Generator
incompletely understood, although new research has elucidated new potential
regulators and key players in the awakening of this system. These include leptin, the
genes GPR54/KiSS-1, as well as several neuropeptides and neurotransmitters.
The increased secretion of androgens from the adrenal gland, called adrenarche, in the
ADRENARCHE
prepubertal and pubertal periods is independent of HPG changes.
-hair growth in the androgen-dependent areas (face, chest, pubic area, axillae). Axillary
and pubic areas are the most sensitive to the effects of androgens, which is why these
What is the Local conversion of DHEA-S to
areas are the first to develop sexual hair.
testosterone and then to
-local conversion of DHEA-S within the apocrine glands of the axillae causes body
dihydrotestosterone is responsible for?
odor,
-conversion within sebaceous glands is responsible for the development of acne.
primarily upon growth hormone and the insulin-like growth factors, but many other
What is the height spurt during puberty hormones may influence growth as well, especially the sex steroids. Without prompt
attributed to? recognition and treatment, premature or delayed puberty may have marked effects on
height.
What is most linear growth contributed to? Growth hormone and its feedback loop
GH secretion is increased by growth hormone-releasing hormone (GHRH) and
decreased by somatostatin from the hypothalamic arm of the loop. Growth hormone
has been shown to double during the pubertal growth spurt. Like many hormones, GH
GH during Puberty
is secreted in pulsatile fashion, with maximum rates at the onset of slow-wave sleep. It is
this pulsatile secretion that renders random testing of GH unhelpful. GH exerts its
effects through IGFs, mainly IGF-I (formerly somatomedin-C) and IGF-II.
Prediction of Final Height for girls (fathers height-13 cm or 5 inches) + mothers height/2