Flashcards in Week 3.0 - Puberty and menopause Deck (53):
-Development of axillary and pubic hair
-First menstrual period
-onset of increased androgen secretion
What is puberty?
-Stage of human development when sexual maturation and growth are completed and results in the ability to reproduce
Who begins puberty first girls or boys?
-Development of breast
Describe the main features of puberty
-Accelerated somatic growth
-maturation of gonads and genitals
-Development of secondary sexual characteristics
-Menstruation and spermatogenesis begins (reproductive system inactive before this)
With what hormonal changes is the onset of puberty associated with?
-Gradual activation of GnRH causing steady rise in FSH and LH
-Increased secretion of oestrogens and androgens
-Extragonadal hormonal changes -> elevation of adrenal steroids and IGF-1
Which hormones is the growth spurt dependent upon?
-Sex steroid hormones
What is the difference between the growth spurt in girls and boys?
-Earlier and shorter in girls
(men are larger because growth spurt longer and slightly faster)
What signifies the end of the growth spurt?
What causes the growth spurt to be shorter in girls?
-Oestrogen closes the epiphyseal plates earlier
What controls the rate of genital development in boys?
When does puberty typically begin in girls?
-8-13 years (mean 11.5 years)
When does puberty typically begin in boys?
-10-14 years (mean 12.5 years)
What is the critical weight for menarche?
What is the relationship between weight and menstruation?
-If weight falls below ~47kgs then reproductive cycle will cease
-Overweight tend to start period early
-Obesity can also interfere with normal menstruation
Name one environmental factor thought to influence puberty?
-Light/dark exposure ie day length
What happens to the LH pulses on lead upto puberty?
-Pulses are negligible and then increase in amplitude and frequency
What is the first phenotypic change in girls?
What is the first phenotypic change in boys?
What is the relationship between sleep and LH?
-LH secretion is associated with REM sleep and begins as nocturnal pulsatility which causes a noturnal increase in sex steroid secretion
What initiates gonadal development in puberty?
-high levels of FSH and LH secretion
What happens after the gonads have started to develop in males?
-Spermatogenesis and androgen secretion begins
-Androgens initiate growth of sex accessory structures (eg prostate) and secondary sex characteristics
The adrenal glands secrete androgens, why does this not initiate puberty?
-Level too low
What is the relationship between TSH and puberty?
-As puberty starts TSH secretion from pituitary increases leading to increased metabolic rate and promotes tissue growth
What effects do androgens have on growth?
-Cause retention of mineral to support bone and muscle growth
Which sex steroid do sertoli cells secrete?
Which secondary sex characteristics are driven by androgens in females?
-Pubic hair growth
-Sebaceous gland secretion
Where are androgens released from in women?
State the order of pubertal changes in girls
-Pubuc hair growth
-Breast development and pubic hair development complete
State the order of pubertal changes in males
-Pubic hair growth
-Genital development and pubic hair development complete
What is tanner staging? explain it
-A method of staging pubertal development
-Different in girls and boys
-Each individual change has 5 stages
eg girls: Breast 1-5, Pubic hair 1-5, Axillary hair 1-5, menarche
boys: Testicular vol >4ml, Penis enlargment 1-5, pubic hair 1-5, axillary hair 1-5, spermache
What initiates the 1st ovarian cycle?
-1st LH surge
Define precocious puberty
-Onset of puberty before the average age
-Before 8 in girls and 9 in boys
How common is precocious puberty?
(much more common in females)
What is the most common cause of precocious puberty?
Besides idiopathic, what are the two types of causes of precocious puberty?
Give an example of gonadotrophin dependant cause of precocious puberty
-Tumour eg hcg secreting tumour
-Nutritional status ie obesity
Give an example of gonadotrophin independent cause of precocious puberty
-Choriocarcinoma of gonads/pineal gland
-Congenital adrenal hyperplasia
What is precocious pseudopuberty?
-Development of secondary sex characteristics without activation of the reproductive system
-Caused by an alternative source of androgen or oestrogen, independent of FSH/LH/GnRH
What is testotoxicosis?
-Familial male precocious puberty
-Autosomal dominant condition where there is rapid skeletal growth, skeletal maturation and sexually aggressive behaviour in the first 2/3 years of life
Define delayed puberty
-Initial physical changes of puberty are not present by age 13 in girls (or primary amenorrhea by 15.5/16) or 14 in males
-Pubertal development is inappropriate ie interval between first signs of puberty and menarche.complete genital growth is >5years
What are the 2 major causes of delayed puberty?
-Gonadal failure (hypergonadotrophic hypogonadism)
Give some causes of gonadal failure
-polyglandular autoimmune syndrome
Give some causes of gonadal deficiency
-Congenital hypogonadotrophic hypogonadism
-Rare genetic mutations inactivating LH/FSH receptors
-typically from age 40
-Follicular phase shortens
-Ovulation becomes early/absent as primary follicles begin to run out-> reduced fertility
-less oestrogen secreted
-Cessation of menstrual cycle for at least 12months
-Average age 49-50
-No more follicles
-Oestrogen levels fall dramatically thus FSH/LH rise dramatically (no inhibin)
Describe the effects of the menopause on oestrogen sensitive tissues
-Thinning of cervix
-Regression of endometrium/myometrium of uterus
-Vaginal rugae lost reducing vaginal tone
-Involution of breast tissue
Describe the effects of the menopause on bone
-Bone mass reduces by 2.5%/year for several years
-Enhanced osteoclast ability to absorb bone and attentuated osteoblastic activity
Describe the purpose of HRT
-Relieve symptoms of menopause and improve well-being
-Can limit osteoporosis
(-given orally or topically)
Why might precocious puberty be stimulated by meningitis?
-Increased pressure due to swollen meninges causing activation of HPG axis