Flashcards in 3.1 Deck (55):
What is puberty?
Sexual maturation and growth completed resulting in ability to reproduce.
What happens in puberty?
Accelerated somatic growth
Maturation of primary sexual characteristic
Appearance of secondary sexual characteristics
Menstruation and spermatogenesis
What the thelarche?
Development of the breast
What is menarche?
First menstrual period.
Equivalent in males is first nocturnal erection and first ejaculation.
What is adrenarche
Onset of an increase in secretion of androgens and pubic hair growth.
When does puberty occur for males and females?
Males: 9-14 years
Females: 8-13 years
What is the first sign of puberty in males? Why?
Increase in testicle size due to FSH induced increase in seminiferous tubules. TEsticular volume up to 4ml
Describe the changes in male puberty.
Genital development - testicle enlargement
Adrenarche - pubic hair growth.
Growth spurt (10cm/year)
Pubic hair adult
When does the growth spurt in males start? How fast is it?
About 12 months after the first signs of puberty.
Describe the female process of puberty.
What age does each occur at?
Thelarche - breast bud 8-11
Adrenarche - pubic hair growth 11-12
Grwoth spurt (9cm/year) 10-14
Menarche - onset of menstrual cycles 11-15
Pubic hair adult
What is the first sign of puberty in females?
Brest bud appearance - thelarche
Why are men on average taller than women?
What are the growth spurt rates? What ends the growth spurt?
Growth spurt is longer and slightly faster. Men = 10cm/year. Women = 9cm/year.
How is pubertal development classified in girls and boys?
Girls: breasts, pubic hair, axillary hair, menarche.
Boys: Testicular volume, penis enlargement, pubic hair, axillary hair, spermarche.
How does growth change in puberty compared to before?
Growth velocity is 2-3 times greater than prepubertal.
WhatHow do hormones control puberty?
GnRH secretion is too low for reproductive function before puberty.
Gradual activation of GnRH increases frequency and amplitude of LH pulses.
Gonadogrophins stimulate secretion of sexual steroids leading to sexual maturation.
Extragonadal hormonal changes lead to somatic growth.
A rise in what hormones is associated with the beginning of puberty?
GnRH, FSH, LH
Initiated by brain
Describe the puberty hormonal changes in males.
Hypothalamus releases GnRH
LH and FSH release increases.
Spermatogenesis and androgen secretion.
Adrenals secrete androgens.
Androgens initiate growth of sex accessory structures (prostate) and male secondary sexual characteristics.
GH secretion increases
Sertoli secrete some oestrogen
TSH secretes increases:
Promotes tissue growth and increases metabolic rate.
Retention of minerals for growth.
Describe puberty hormonal changes in females.
Oestrogen induces secondary sexual characteristics:
Pelvis growth, subcutaneous fat
Growth of internal repro organs and external genitalia.
Androgen release by adrenal glands increases:
Growth of pubic hair
Lowering of voice
Growth of bone
Increased sebaceous gland secretion.
What initiates the first ovarian cycle?
Usually insufficient to cause ovulation.
Describe the hormonal changes in the pre-follicular phase.
Corpus luteum absent
Follicles only partly developed
Secrete very little steroid or inhibin
O and P low
Little inhibition at hypothalamus or pituitary
FSH levels rise
Describe the hormonal changes at the mid-follicular phase.
Oestrogen levels rise
Inhibin levels rise.
Selective inhibition of FSH
No new follicles can develop.
Oestrogen exerts positive feedback at hypothalamus and pituitary
LH levels rise.
Describe the hormonal changes in ovulation
LH surge preceded by rise in oestrogen
Describe the hormonal changes post ovulation
Corpus luteum forms spontaneously
Begins to secrete oestrogen and progesterone.
Maintains suppression of FSH - no new follicles.
LH is also suppressed as positive feedback of oestrogen is inhibited by progesterone.
Describe the start of the new cycle.
Death of corpus luteum --> Corpus albicans
Leads to rapid fall in steroid levels
Relieves inhibition on FSH - follicular development.
How is adrenarche controlled?
Depends on androgen in both sexes
Testosterone in boys
From adrenal in girls.
What is the critical weight for menarche? What happens if body weight falls below this?
Reproductive cycle ceases.
Why has puberty got earlier through the generations? Evidence for this?
Earlier puberty due to improved nutrition, living conditions and healthcare.
Obese girls go through menarche early.
Malnutrition associated with delayed menarche.
Primary amenorrhoea common in lean female athletes.
Body fat set point is very noticeable in girls with fluctuating body weight.
When does the growth spurt start (Weight) in boys and girls?
30 kg in girls
55kg in boys
What does the growth spurt depend on?
GH and steroids in both sexes.
What causes growth spurt to end earlier in girls
Oestrogen closes epiphyses earlier.
Oestrogen is needed to initiate growth spurt but once levels reach a certain point, it causes epiphyseal fusion.
How is thelarche controlled?
Dependent on oestrogens.
How is genital development controlled in boys?
What is precocious puberty?
Onset of puberty 2SD before average age.
Before 8 in girls and before 9 in boys
What can precocious puberty be caused by?
Uncontrolled gonadotrophin/steroid secretion (gonadotrophin dependent)
Neurological causes (gonadotrophin independent)
Give some causes of gonadotrophin dependent precocious puberty.
Hormone secreting tumours
Gliomas, astrocytomas, hCG secreting germ cell tumours
CNS trauma or injury
Congenital disorders - hydrocephalus
Hamartoma of hypothalamus.
Exogenous exposure - therapeutic/accidnetal
Give some causes of gonadotrophin independent precocious puberty.
Inappropriate GnRH secretion caused by:
How can meningitis cause precocious puberty?
Inflammation leading to early increase in GnRH release from hypothalamus, independent of HPG axis
What is precocious pseudo puberty? Cause? Consequence?
Appearance of secondary sexual characteristic early.
Due to increased production of female or male hormones independently of HPG axis.
Congenital adrenal hyperplasia --> androgens
Gonad matures without GnRH stimulation.
Levels of testosterone and oestrogen are elevated.
How to delay precocious puberty?
Testosterone inhibitor/GnRH anologues(competitive inhibitor)
What are the effects of precocious puberty on growth and stature?
Early growth spurt initially can cause tall stature but rapid bone maturation and sealing of epiphyses can cause linear growth to cease early, resulting in short adult stature.
What is bone age?
Accelerated growth is earliest sign of precocious puberty.
Can be determined with hand-wrist films and compared with standards for chronological age.
What is delayed puberty?
Initial changes are not present by
13 years in girls
14 years in boys
Pubertal development is inappropriate:
Interval between first signs and menarche of completion of male genital growth > 5 years
How can puberty be assessed?
Height, weight, genitals, body hair, bone age
What are causes of delayed puberty?
Hypergonadotrophic hypogonadism (Gonad failure)
Turner's 45, XO
Congenital hypogonadotrophic hypogonadism (gonad deficiency)
Hypothalmic pituitary lesions\Rare gene mutations inactivating FSH and LH
How does Turner's present?
Cardiac and kidney malfunction
No mental/cognitive defect
How can delayed puberty present in girls? What is this due to if LH/FSH levels are normal?
LH FSH low?
Primary amenhorrhoea - Failure to menstruate by 16 years
Ovaries are not responding to gonadotrophins
What is pre-menopause?
> 40 years?
Changes in menstrual cycle:
Follicular phase shortens
Ovulation early or absent
- Less oestrogen secreted
- Less negative feedback so LH and FSH levels rise
- FSH rises more due to loss of inhibit
- GnRH rises
- Reduced feedback --> reduced fertility
What is the menopause?
Cessation of the menstrual cycle.
Females run out of follicles
Oestrogen levels fall dramatically
Less negative feedback so FSH and LH rise
FSH dramatically due to no selective inhibition
What are the effects of menopause?
Hot flushes due to vascular changes
- Regression of endometrium
- Shrinkage of myometrium
Thinning of cervix
Vaginal rugae lost
Involution of breast tissue
Changes in skin
Reduction in bladder tone
What are the bone changes in menopause? How are they limited?
Reduction in bone mass by 2.5% per year for several years.
Reduced oestrogen enhances osteoclast ability to absorb bone.
Can lead to osteoporosis:
Increased risk of fracture.
Limited by bisphosphonates oestrogen therapy and calcium.
How do you treat hot flushes in post menopause?
Relieves symptoms of menopause
Can improve well-being
Oestrogen given orally or topically by patch or gel.
Usually a mix of oestrogen and progesterone.
Not advised for cardio protection
Give advantages of HRT
Can limit osteoporosis
Lowers risk of colon cancer
Lowers risk of vision loss and macular degeneration.
Give disadvantages of HRT
Increased risk of ovarian cancer