Week 3.0 - Puberty and menopause Flashcards
Define Puberache
-Development of axillary and pubic hair
Define menarche
-First menstrual period
Define adrenache
-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?
-Girls
Define thelarche
-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?
- Growth Hormone
- 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?
-Epiphyseal fusion
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?
-Testosterone
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?
-47kg
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
- Altitude
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?
-Breast development
What is the first phenotypic change in boys?
-Testicular enlargement
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?
-Oestrogen
Which secondary sex characteristics are driven by androgens in females?
- Pubic hair growth
- Bone growth
- Sebaceous gland secretion
Where are androgens released from in women?
-Adrenals
State the order of pubertal changes in girls
- Thelarche
- Pubuc hair growth
- Growth spurt
- Menarche
- Breast development and pubic hair development complete
State the order of pubertal changes in males
- Genital deveopment
- Pubic hair growth
- Spermatogenesis
- Growth spurt
- 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?
-1/5000-10,000
much more common in females
What is the most common cause of precocious puberty?
-Idiopathic
Besides idiopathic, what are the two types of causes of precocious puberty?
- Gonadotrophin dependant
- Gonadotrophin independent
Give an example of gonadotrophin dependant cause of precocious puberty
- Tumour eg hcg secreting tumour
- Trauma
- Nutritional status ie obesity
Give an example of gonadotrophin independent cause of precocious puberty
- Choriocarcinoma of gonads/pineal gland
- Meningitis
- 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
Either:
-Initial physical changes of puberty are not present by age 13 in girls (or primary amenorrhea by 15.5/16) or 14 in males
or
-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)
- Gonadal deficiency
Give some causes of gonadal failure
- Turners syndrome
- Post-malignancy treatment
- polyglandular autoimmune syndrome
Give some causes of gonadal deficiency
- Congenital hypogonadotrophic hypogonadism
- Hypothalamic/pituitary lesions
- Rare genetic mutations inactivating LH/FSH receptors
Describe pre-menopause
- typically from age 40
- Follicular phase shortens
- Ovulation becomes early/absent as primary follicles begin to run out-> reduced fertility
- less oestrogen secreted
Describe menopause
- 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
- Urinary incontinence
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
- Osteoporosis
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
Would you expect a female to be taller or shorter with precocious puberty? why?
-Shorter due to early closure of epiphyseal growth plates
