Hormones and Regulation Flashcards
Puberty
Developmental changes a child undergoes to become sexually mature and physiologically ready for reproduction
Females:8-14
Males: 10-16
Control of puberty and reproductive system
Hormones of Hypothalamic-Pituitary-Gonodal Axis
Hypothalamus releases GnRH in pulsatile manner.
stimulates release of FSH and LH from anterior pituitary gland
Role of FSH and LH
Act on gonads to stimulate synthesis and release of sex steroid hormones nd support gametogenesis
Rise in FSH
Increase in oestrogen synthesis and oogenesis in females and onset of sperm production in males
Rise in LH
Stimulates an increase in production of progesterone in females and an increase in testosterone production in males
Physical Changes during puberty - Females
Thelarche
- Breast development
Pubarche
- Growth of hir in pubic area
- mediated by testosterone
Menarche
- First menstrual period
- Arises due to increase in FSH and LH
Physical Changes during puberty- males
Genital Changes
- Increase in testicular size
- Growth of scrotal skin
- Growth of panic
Pubarche
Growth spurt
Product of complex interaction between gonadal sex steroids (estradiol/ testosterone), GH and insulin-like growth factor (IGF-1)
GH levels rise in puberty due to increase in sex steroids and their positive effect on pulsatile release of GH from anterior pituitary gland
RIse in GH causes a rise an anabolic hormone IGF-1, csauses somatic growth via its metabolic actions
Precocious puberty
appearance of secondary sexual characteristics before
Causes/ types of precocious puberty
Iatrogenic
- result of exposure to exogenous oestrogen
True/ complete
- early maturation of HPG axis resulting in high level of GnRH, FSH and LH. My be due to CNS lesions near or in posterior hypothalamus, CNS neoplasms, harmatomas, primary hypothyroidism
Incomplete
- increased level of oestrogen in girls and androgens in boy that are independent of GnRH
Delayed/ absent puberty
Absence of secondary sexual characteristics by age of 13 in girls or 16 in boys
Causes of delayed/absent puberty
Hypogonadotrophic hypogonadism
Hypergonaadotropic hypogonadism
Conditions associated with delayed/ absent puberty
Turner’s Syndrome (45 XO)
Klinefelter’s Syndrome (47 XXY)
Androgen Insensitivity syndrome
Kallmann Syndrome
Normal duration of menstrual cycle
21-35 days
regulation of menstrual cycle
Hypothalamus, anterior pituitary and ovaries
GnRH from hypothalamus stimulates LH and FSH release from anterior pituitary gland.
Role of LH and FSH in menstrual cycle
Gonadotrophins that act primarily on the ovaries.
FSH: binds to granuloma cells to stimulate follicle growth, permit conversion of androgens (from theca cells) to oestrogen and stimulate inhibit secretion
LH: acts on theca cells to stimulate production and secretion of androgens.
Feedback systems controlling menstrual cycler
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 oestrogen exerts negative feedback on HPG axis.
Inhibin selectively inhibits FSH at anterior pituitary.
Ovarian cycle
Follicular Phase
Ovulation
Luteal Phase
Follicular Phase
Beginning of new cycle.
Follicles begin to develop independently of Gonadotropins.
Increase in FSH and LH
Stimulate follicle growth and oestrogen production
Rise of oestrogen- negative feedback reduces FSH levels.
Only one follicle can survive
Follicular oestrogen becomes high enough to potentiate +ve feedback at HPG- increasing GnRH and Gonadotropins
LH levels increase.
Granulosa cells luteinised and become receptors for LH
What do non-dominant follicles form
Polar bodies
Ovulation
In response to LH surge, follicle ruptures and mature oocyte is assisted to Fallopian tube by fimbria.
Remains viable for fertilisation for ~24 hours.
Following ovulation, follicle remains luteinised, secreting oestrogen and progesterone,
Reverts to -ve feedback on HPG axis.
Negative feedback + Inhibin ->stalls cycle in anticipation of fertilisation
what tissue forms in ovary at site of rupture follicle following ovulation
+ what is its role
corpus luteeum,
Produces oestrgoens, progesterone and Inhibin to maintain conditions for fertilisation and implantation
Luteal phase
Formation of corpus lute. At end of cycle in absence of fertilisation, corpus luteum spontaneously regresses after 14 days.
Significant fall in hormones, relieving negative feedbackl, resetting HPG axis
Fertilisation
If fertilisation occurs, syncytiotrophoblast of embryo produces HcG exerting luteinising effect -> maintaining corpus luteum.
Supported by placental HcG and produces hormones to support pregnancy.
Uterine cycle phases
proliferative
secretory
menses
Proliferative phase
Runs alongside follicular phase.
Prepares reproductive tract for fertilisation and implantation.
Oestrogen inhibits fallopian tube formation, thickening of endometrium, increased growth and motility of myometrium and production of thick alkaline cervical mucous.
Secretory phase
Runs alongside luteal phase
Progesterone stimulates
- further thickening of endometrium into glandular secretory form.
- thickening of myometrium -reduction of motility of myometrium
- thick acidic cervical mucus production
- changes in mammary tissue
- other metabolic changes
Menses
Marks beginning of new menstrual cycle.
Occurs in absence of fertilisation once corpus luteum has broken down and internal lining of uterus is shed
menstrual bleeding usually lasts 2-7 days with 10-80ml blood loss
Dysmenorrhoea
Painful periods
Endometriosis
Growth of endometrial tissue outside of the uterus
menopause
end of female reproductive life.
physiological process which begins as perimenopause at ~45 and progresses until final menopause’s and end of fertility
Menopause is defined when a women has had amenorrhoea for 12 months.
early menopause
before 45 years
perimenopausal
women progressing towards menopause
hormone changes during menopause
reduction of circulating oestrogen
- reduced sensitivity of ovary to circulating gondaotropins
Increase in anovulatory cycles
Significant increase in FSH and lH
- low levels of circulating oestrogen
- decrease in developing follicle reduces amount of Inhibin release
vasomotor changes during menopause
hot flushes
associated with peripheral vasodilation and transient rise in body temperature.
Pulsatile LH relese influences central temperature control
urogenital changes during menopause
decrease in oestrogen
- marled atrophy of vagina and thinning of myometrium.
can result in dyspareunia
Bladder and urethra can also atrophy. Lead to symptoms of urinary incontinence and increase in UTIs
bone density in menopause
oestrogen protects bone mass and density through reducing activity of osteoclasts.
Drop in oestrogen causes increase in bone resorption.
results in acceleration of age-related loss of bone density and increased frequency in fractures.
ischaemic heart disease and menopause
oestrogen offers protective effect against her disease.
Oestrogen reduces levels of LDL cholesterol whilst raising HDL cholesterol.
