3.1 lecture: endocrinology 'Puberty and Menopause' Flashcards
what is Thelarche?
development of breast
what is Puberache?
development of axillary & pubic hair
what is Menarche?
the first menstrual period
what is Adrenarche?
the onset of an increase in the secretion of androgens
what is puberty?
A stage of human development when sexual maturation and growth are completed and result in ability to reproduce
what happens during puberty?
– Accelerated somatic growth
– Maturation of primary sexual characteristics (gonads and genitals)
– Appearance of secondary sexual characteristics (pubic and axillary hair, female breast development, male voice changes,…)
– Menstruation and spermatogenesis begin
which organ initiates puberty?
brain
what is onset of puberty associated with? why?
steady increase in FSH and LH
due to increase in GnRH secretion
when can most parts of reproductive system work before?
Most parts of the reproductive system can work before normal age of puberty
why does the reproductive system not function before the normal age of puberty?
because hormone levels are low
due to low GnRH (from hypothalamus - brain initiates puberty)
what does growth spurt depend upon?
Depends on growth hormone and steroids in both sexes
why are men taller?
Men larger because growth spurt longer and slightly faster (10cm instead of about 9cm/year)
what does Genital development in boys depend upon?
testosterone
when does growth spurt occur in girls compared to boys?
earlier and shorter in girls
what marks the end of growth spurt in both genders?
closing of epiphyseal growth plates (epiphyseal fusion)
why do girls growth spurt end earlier?
Oestrogen closes epiphyses earlier in girls
what happens to girls if there is a significant weight loss?
reproductive cycles cease
what is one of the contributing factors of puberty?
nutrition
(especially earlier puberty)
(living conditions, healthcare)
what is the most important contributing factor of puberty?
body weight (girls: 47kg before menarche, boys: 55kg)
what may be involved in signalling for initiation of puberty?
leptin (fat hormone)
what is a factor associated with delayer menarche?
malnutrition
what is primary amenorrhea common in?
lean female athletes
what is ‘body fat’ set point very noticeable in?
girls with fluctuating body weight due to anorexia nervosa
in mammals breeding seasonally, what is puberty each year associated with?
– Triggered by changes in day length
– Involvement of pineal gland
– Secretion of melatonin
which tumour can influence puberty in humans?
pineal tumours
what does puberty hormonal changes precede in humans?
physical changes
what do the puberty hormonal changes cause in humans?
Increased stimulation of hypothalamo-pituitary-gonadal
axis (HPG) - from hypothalamus increasing GnRH pulses
what are the puberty hormonal changes? (HPG axis)
– gradual activation of the GnRH
– increases frequency and amplitude of LH pulses (from increase GnRH)
– gonadotropins (FSH/LH) stimulate secretion of sexual steroids (oestrogenes and androgenes)
what are the extragonadal hormonal changes associated with puberty hormonal changes (HPG axis)
elevation of IGF-I,
and adrenal steroids
what does GH secretion from pituitary cause?
- Increases TSH
- increases metabolic rate
- promotes tissue growth
- increase androgens = retention of minerals in body to support bone and muscle growth
what does GH secretion from pituitary result in?
growth spurt
what does GH secretion from pituitary cause (hormones / metab)?
- Increases TSH (so more T3/T4)
- increases metabolic rate
- promotes tissue growth
- increase androgens (oestrogen/testosterone) = retention of minerals in body to support bone and muscle growth
what does GH secretion from pituitary result in?
growth spurt
what are the first phenotypic changes in females puberty?
breast development
what are the first phenotypic changes in males puberty?
testicular enlargement
what precedes phenotypic changes by several years?
Nocturnal GnRH pulsatility (LH secretion)
what does sleep dependent nocturnal rise in LH suggests in adolescent boys? (HPG axis)
in adolescent boys, the sleep related LH (AP) increases
stimulating a nocturnal rise of testosterone (gonads)
what does the nocturnal rise in testosterone stimulated by LH account for?
some of the early pubertal changes seen in males
what is the similar pattern of early pubertal changes seen in females stimulated by?
concomitant increase in oestrogen
at which age do blood levels of LH,FSH increase? how?
9-12 years
amplitude of pulses increase, especially during sleep
what does high blood levels of LG, FSH lead to between 9-12 years?
initiate gonadal development
young children, LH + FSH levels insufficient to initiate gonadal function
when do FSH and LH increase in males? leading to?
LH + FSH increase at about 10 years
spermatogenesis, androgen secretion from adrenals
what does androgens released from adrenal glands initiate in males?
growth of sex accessory structures (e.g. prostate)
male secondary sex characteristics (facial hair, growth of larynx - voice breaks)
what induces secondary sex characteristics in females?
oestrogen
what are the secondary sex characteristics in females?
growth of pelvis (more lateral acetabulum)
deposit of subcutaneous fat
maturation of internal reproductive organs
development of external genitalia
what does androgens released by adrenal glands in female cause?
growth of pubic hair
growth of bone
increased secretion from sebaceous glands
