Repro Session 3 Flashcards
What is pubarche?
Development of axillary and pubic hair
What is menarche?
1st menstrual period
What is adrenarche?
Onset of an increase in androgen secretion
What is puberty?
Stage of human development when sexual maturation and growth are completed form the primary sexual characteristics established before birth
What is the fixed order of events seen in puberty?
Accelerated somatic growth, maturation of primary sexual characteristics, appearance of secondary sexual characteristics, menstruation/spermatogenesis begin
What accounts for the 10% difference in height between men and women?
Women undergo somatic growth earlier and for less time due to closure of epiphysis by oestrogen
What does genital maturation depend on in males?
Testosterone
Why does the reproductive system not work before puberty?
Low GnRH secretion –> low hormone levels so LH and FSH are insufficient
Where is there low level androgen secretion from prior to puberty?
Adrenals
What initiates onset of puberty?
Brain increasing GnRH –> steady rise in LH and FSH
How does nutrition affect onset of puberty?
Critical weight of 47 kg of menarche needs to be met and correlation between leptin and menarche
What is the supporting evidence that nutrition influences the onset of puberty?
Obese girls experience early menarche, malnutrition –> delayed menarche, primary amennorhoea in lean athletes, body fat set point seen in girls with fluctuating weight due to anorexia nervosa
What suggests an association between onset of puberty and seasonal breeding seen in species where changes in day length alter pineal gland melanin secretion?
Pineal tumours influencing onset of puberty in humans
What action does TSH have in both sexes in the HPG axis?
Increases metabolic rate and promotes tissue growth
What are the results of increased growth hormone on the HPG axis in puberty?
Increases insulin to descrease sex-hormone binding globulin and IGF-gpbinding protein and acts on liver to increase IGF-1 to cause somatic and neuronal growth and myelin secretion
What precedes the phenotypic changes seen in puberty by several years?
Increase in nocturnal pulsatile LH secretion during REM sleep
What happens at 9-12 years to lead to gonadal development?
(Less sensitive hypothalamic neurones?) LH and FSH levels rise
What are the results of the LH and FSH rise at ~10 y.o. In males?
Spermatogenesis and androgen secretion
What are the affects of increased androgen secretion in males during puberty?
Growth of sex accessory structures (prostate), male secondary sex characteristics, retention of mineral in body for bone and muscle growth
Which cells in the male secrete oestrogen?
Sertoli
What is the pattern of phenotypic changes seen in male puberty?
Testicular volume increases –> public hair grows and spermatogenesis occurs –> growth spurt –> adult genitalia and pubic hair develop
What is the pattern of phenotypic changes seen in female puberty?
Thelarche and pubic hair growth –> adrenarche, growth spurt and onset of menstrual cycle –> menarche, adult pubic hair and breasts
What are the female secondary sex characteristics?
Growth of pelvis, SC fat, reproductive organ and genitalia growth
What effects does increasing androgen release by the adrenal glands have on the female during puberty?
Growth of public hair, lowering of voice, growth of bone and increased secretion from sebaceous glands
Is the LH surge in the first ovarian cycle usually enough for ovulation?
No
What is considered normal pubertal development in boys?
Age of start (yrs): 12.5
First sign of puberty: testicular volume
What is considered normal pubertal development in girls?
Age of start (yrs): 11.5
First sign of puberty: breast development
Growth velocity (cm/yr): 9.0
Duration (yrs): 2.4 +/- 1.1
What are the 5 stages of Tanner standard for girls?
Breast: B1-5
Pubic hair: Pu1-5
Axillary hair: A1-5
Menarche
What are the 5 stages of Tanner standard used in male puberty?
Testicular volume > 4 ml: Te Penis enlargement: G1-5 Pubic hair: Pu1-5 Axillary hair: A1-5 Spermarche
How does prepubertal and pubertal growth velocity compare?
Pubertal approx 2/3 X greater than prepubertal
When does male puberty usually occur?
9-14 y.o.
When does female puberty usually occur?
8-13 y.o.
What affects the precise timing of the LH surge during the ovarian cycle?
Environmental factors such as day length and altitude
What is precocious puberty?
Onset of puberty >2 s.d. before average age (girls
What is the prevalence of precocious puberty?
1 in 5000 to 1 in 10,000
What two types of precocious puberty are there?
Gonadotrophin dependent (central) and gonadotrophins independent (neurological)