Development and Maturation

Question 1

When does puberty usually occur?

Answer 1

8-14 in females

10-16 in males

Question 2

Hormonal changes of puberty

Answer 2

Hypothalamus releases GnRH in pulsatile manner which stimulates release of FSH and LH from anterior pituitary
FSH/LH act on gonads to stimulate synthesis and release of sex steroid hormones
Rise in FSH -> oogenesis in females and onset of sperm production in males
Rise in LH -> increase in progesterone in females and testosterone in males

Question 3

Physical puberty changes in females

Answer 3

Thelarche
- beginning of breast development
- increased oestrogen causes development of lactiferous duct system and lobular alveoli
Pubarche
- growth of hair in pubic area
- initially sparse, light and straight but becomes coarser, thicker and darker
- secondary sexual characteristic mediated by testosterone
Menarche
- 1st menstrual period - 12.8 years

Question 4

Physical puberty changes in males

Answer 4

Increase in testicular size
- LH stimulates testosterone synthesis my Leydig cells
- FSH stimulates sperm production by sertoli cells
Growth in penis size - height and width
Pubarche
- growth of pubic hair at base of penis
- growth on legs, arms, axillae, chest and face

Question 5

Physiology of growth spurts

Answer 5

Interaction of gonadal sex steroids (oestradiol/testosterone), GH and IGF-1
Rise of IGF-1 causes somatic growth via metabolic actions - increases trabecular bone growth

Question 6

Precocious puberty

Answer 6

Appearance of secondary sexual characteristics before age of 8 in girls or 9 in boys

• Iatrogenic - exposure to exogenous oestrogens
• true/complete - due to early maturation of HPG axis resulting in high levels of GnRH, FSH and LH
• incomplete - due to increased levels of oestrogen/androgens that are independent of GnRH

Question 7

Delayed/absent puberty

Answer 7

Absence of secondary sexual characteristics by age of 13 in girls or 16 in boys
- hypogonadotropic hypogonadism - deficiency of GnRH, LH or FSH
- hypergonadotropic hypogonadism - absent or reduced steroid secretion -> high FSH and LH levels
Treat carefully with controlled HRT

Question 8

Menstrual cycle HPG axis

Answer 8

Gonadotropin releasing hormone (GnRH) from hypothalamus stimulates LH and FSH release from anterior pituitary

• FSH binds to granulosa cells to stimulate follicle growth, permit conversion of androgens to oestrogen and stimulate inhibin secretion
• LH acts on theca cells to stimulate production and secretion of androgens

Question 9

Menstrual cycle feedback systems

Answer 9

Moderate oestrogen levels exert negative feedback on HPG axis
High oestrogen levels (in absence of progesterone) positively feedback on HPG axis
Oestrogen in presence of progesterone exerts negative feedback on HPG axis
Inhibin selectively inhibits FSH at the anterior pituitary

Question 10

Ovarian cycle

Answer 10

Follicular Phase
- increase in FSH and LH stimulate follicle growth and oestrogen production
- one dominant follicle and polar bodies form
- oestrogen becomes high enough to inhibit positive feedback
- LH surge due to increased follicular inhibin
Ovulation
- LH surge follicle ruptures and mature oocyte release
- follicle remains luteinised secreting oestrogen and progesterone
Luteal Phase
- corpus luteum produces oestrogens, progesterone and inhibin
- regresses spontaneously after 14 days if no fertilisation
- if fertilisation occurs syncytiotrophoblast produces HcG maintaining corpus luteum

Question 11

Uterine Cycle

Answer 11

Proliferative Phase
- oestrogen initiates fallopian tube formation, thickening of endometrium, increased growth and motility of myometrium and production of think alkaline cervical mucus
Secretory Phase
- progesterone stimulates further thickening of endometrium to glandular secretory form
- reduction in mobility of myometrium, thick acidic cervical mucus production and changes in mammary tissues
Menses
- corpus luteum breaks down and lining of uterus is shed

Question 12

The menopause

Answer 12

Begins with perimenopause at around 45
Progresses until the final menses and end of fertility - average age is 51
Menopause = amenorrhoea for 12 months

Question 13

Hormonal changes during menopause

Answer 13

Reduction in circulating oestrogen - reduced sensitivity of the ovary to circulating FSH and LH
Increase in anovulatory cycles
Decrease in developing follicles reduces amount of inhibin
Levels of FSH and LH increase significantly and remove negative feedback on hypothalamus and pituitary gland

Question 14

Vasomotor changes of menopause

Answer 14

Hot flushes

• associated with peripheral vasodilation and transient rise in body temp
• pulsatile LH

Question 15

Urogenital changes of menopause

Answer 15

Uterus and vagina maintained by circulating oestrogen
Marked atrophy of vagina and thinning of myometrium
Thinning of vaginal wall and dryness -> dyspareunia

Question 16

Changes to bone density of menopause

Answer 16

Oestrogen protects bone mass and density through reducing activity of osteoclasts
With reduced oestrogen increase in bone reabsorption
Acceleration of age related loss of bone density and increased frequency of fractures

Question 17

Menopause and ischaemic heart disease

Answer 17

Oestrogen offers protective effect against heart disease

- reduces levels of LDL cholesterol whilst raising HDL