Puberty and Menopause Flashcards
Define Thelarche, pubearche, menarche and adrenarche
Thelarche – development of the breasts
Puberache – development of pubic hair
Menarche – the first menstrual period
Adrenarche – the onset of an increase in the secretion of androgen
What is puberty?
Primary sexual characteristics established before birth but reproductive system inactive until puberty.
Puberty – stage of human development when sexual maturation and growth are completed and result in ability to reproduce
What are the general aspects of puberty?
Accelerated somatic growth
Maturation of primary sexual characteristics
Appearance of secondary sexual characteristics
Menstruation and spermatogenesis begins
How is puberty initiated?
Puberty initiated by the brain associated with a rise in FSH and LH due to a rise in GnRH. Reproductive structural system is all present at birth – puberty kicks it all into action. Thus, it is possible for puberty to begin to early – precocious puberty. However usually this doesn’t happen as GnRH secretion is low.
How do growth spurts differ between boys and girls?
Growth spurt starts earlier in females and ends earlier whilst in boys it starts later ends later and reaches higher. Growth plates closed by oestrogen.
How and why has the timing of puberty changed in the past few 100 years?
Used to be that girls didn’t start puberty until 17 years but now it’s more around 13 years. Thought to be to do with weight specifically hitting 47kg.
What evidence is there supporting the nutritional hypothesis of the initiation of puberty?
Evidence supporting the nutrition hypothesis – malnutrition associated with delayed menarche, primary amenorrhoea common in lean female athletes and body fat set point very noticeable in girls with fluctuating body weight due to anorexia nervosa (loss of appetite and refusal to eat).
Weight loss causes reproductive cycles to cease. Nutrition and body weight plays a large contributing factor to time of puberty starting. Leptins also involved. .
In animals what environmental factors play a role?
In some species breeding is seasonal so there is a new puberty each year triggered by day light ours and melatonin – pineal gland very important with this in animals. Pineal tumours can cause pernicious puberty.
What hormonal changes take place in puberty?
Increased stimulation of the HPG axis causes a gradual increase in the release of GnRH resulting in an increase in frequency and amplitude in LH bursts. Gonadotrophins stimulate secretion of sexual steroids. Extragonadal hormonal changes (elevation of IGF-I and adrenal steroids) also influence changes at puberty.
What stimulates the initial rise in GnRH?
The GnRH release is stimulated by the Kiss 1 neuron arcuate area of the brain which releases a peptide called kiss resulting in the initial kick start for puberty to occur. Leptin then has a positive feedback on this cascade. The gonadal steroids have a negative feedback effect on Kiss 1 allowing the system to be regulated.
What other hormonal changes are there that are not related to the HPG axis?
GH secretion increases TH, metabolic rate, promotes tissue growth, increased androgens results in retention of minerals in body to support bone and muscle growth this results in a growth spurt.
What is the time lag between the first hormonal changes and the first phenotypic changes, what are the first phenotypic changes that are seen?
Nocturnal GnRH pulsatility (and so LH secretion) precedes phenotypic changes by several years. First phenotypic changes are breast development and testicular enlargement.
What is the significance of the rise in LH and FSH at night during puberty?
In young children LH and FSH levels are insufficient to initiate gonadal function. Between 9-12 years’ blood levels of LH and FSH increase. Amplitude of pulses increases especially during sleep. High levels of LH and FSH initiate gonadal development.
What do the hormonal changes cause to happen in girls?
Oestrogen induces 2nd sex characteristics – growth of pelvis, deposits of fat, development of internal repro organs and external genitalia. Androgens released by adrenal glands increases growth of pubic hair, growth of bone, increased secretion from sebaceous glands.
What is the tanner staging method?
Pubertal development is staged using the tanner standard which has 5 different stages. This stages focus on certain aspects of puberty. For females, this occurs between 9-13 years, this is: breasts, pubic hair (occurs after breast development beginning), axillary hair and menarche (about 12 years). For males, this is: testicular volume, penis enlargement, pubic hair, axillary hair and spermarche.
