Sex hormones Flashcards
What is the definition of puberty?
Maturation of reproductive organs; production of sex steroids (Oestradiol/Testosterone); development of secondary sexual characteristics and attaining the capability to reproduce
What is thelarche?
Onset of breast development
What is Gonadrche?
Activation of gonads by HPG axis
What is menarche?
The first occurrence of menstural cycles
What is adrenarche?
Adrenal androgen productiion
When does adrenarche occur in comparison to Gonadrche?
onset 2 years before Gonadrche
What is pubarche?
Onset of pubic hair development
What are the main effects of oestradiol?
Breast development, hair growth (Pubic & axillary), sweat gland composition, skin oiliness/acne
Changes to external genitalia
What is the first strage of thelarche?
Elevation of papilla
What is stage 3 thelarche?
Further enlargement of breast and papilla, separation of their contours
What is stage 5 of thelarche?
Adult: Mature breast, projection of papilla only as areola conforms to breast contour
What are the main effect of testosterone?
Deepening of voice
Hair growth, pubic, axillary & facial
Sweat gland composition, skin oiliness and acne
Changes to externa genitalia
For which gender is the age of onset earlier?
Females
What is the age of onset for females?
8-13 years
What is the age of onset for boys?
9-14 years
Which stage occurs first in females? Adrenarche or menarche?
Adrenarche
What is the first sign for females?
Thelarche
What is the latest female pubertal sign?
Menarche
What is the age of onset of puberty for males?
9-14 years
What is the average testicular size for prepubertal males?
4 mls
What is adult size of testicular volume?
15mls
Which molecule is an adrenal androgen which increases with age?
DHEA
Which gonadotrophs are released during gonadrche?
FSH & LH
Which neurones are associated with the hypothalamus and control pulsatility?
Kisspeptin neurones
What is the role performed by kisspeptin neurones?
Regulate the pulsatile secretion of Gonadotrophin-releasing hormone (GnRH) from parvocellular hypothalamic neurones into the primary capillary plexus within the median eminence
Which circulation do hypothalamic hormones circulate within?
Hypophyseal-pituitary circulation
Which hormones are released upon GnRH stimulation?
LH & FSH
Which cells secrete LH and FSH?
Gonadotrophs
Where are gondatrophs situated?
Anterior pituitary gland
Which organs are stimulated by the action of LH & FSH?
Testes and ovaries
When is there an increase in GnRH pulsatility?
During Gonadrche there is an increased nocturnal GnRH pulsatility, towards a new equilibrium steady rate during adulthood
What happens to the HPG axis during childhood?
There is quiescence
What is mini puberty?
Stimulates the early development and maturation of sex-organs –> Increased risk of Mal-descent of the testes & micro-penises
What is the consequences of mini-puberty?
Mal-descent of testes and micro-penises
What is the consequence of a continuous non-pulsatile administration of GnRH?
Causes decreased LH/FSH secretion
Delayed onset of puberty is more common with which gender?
Males
What term describes an early onset of puberty?
Precocious
What is the precocious age of onset for females?
<8 years
What is the average delayed age of onset for males?
14 years
When does menarche occur after thelarche?
2.3 years, immediately after peak height velocity
What is the mean age for menarche?
12.7 years (Range 10.7-16.1 years)
What is amenorrhoea?
Absence of periods
What is the definition of primary amenorrhoea?
Later than 16 years is regraded as abnormal, delayed menstrual cycle onset
What is secondary amenorrhoea?
Common for irregular/anovulatory periods for initial 18 months. Periods begin, however cease for 3-6 months
What is the average number of annual periods with patients experiencing secondary amenorrhoea?
3
What is oligo-menorrhoea?
Irregular or infrequent periods > 35 day cycles (4-9 cycles annually)
How long is a standard menstrual cycle?
28 day cycle
What is the first phase of the menstrual cycle?
Follicular phase
Which hormone rises during the follicular phase?
FSH
What is the average number of follicles that grow during the follicular phase?
2-3 follicles
What hormones are produced by the follicular phase?
Inhibin and E2
What effect is exerted by inhibin and E2 on FSH secretion?
Negative feedback effect on FSH secretion on the hypothalamus and on the anterior pituitary gland
What happens to non-dormant follicles during the follicular phase?
They undergo atresia
What term is used to describe a dominant follicle?
Graafian follicle
What happens to the E2 concentration during the follicular phase?
E2 concentration continues to increase, positive feedback switch exerted by E2
What effect is exerted by a positive feedback switch by E2?
Induces luteinising hormone surge
What happens due to the induction of LH?
Stimulates ovulation, secretion of the mature secondary oocyte from the Graafian follicle
What is the term used to describe the remnant follicle upon ovulation of secondary oocyte?
Corpus luteum
What phase follows the follicular phase?
Luteal phase
Which hormone develops the corpus luteum?
LH
Which hormone is released from the corpus luteum?
Progesterone
Which hormone maintains the endometrium lining?
Progesterone
What test can be conducted to identify ovulation?
Progesterone level test for mid-luteal phase
What effect does progesterone have?
Maintains endometrium lining
What effect does decreased progesterone have on FSH?
Reduced negative feedback, stimulates FSH levels, oestradiol is secreted
Why does the corpus luteum degrade?
Due to absent HCG stimulation
The reduction of progesterone results in what?
Shedding of the endometrium lining - mensural cycle occurs
What hormone is tested in pregnancy tests?
Beta HCG
Which receptors are activated by beta HCG?
LH and FSH receptors - continues to support the corpus luteum - secretes progesterone
Which hormonal receptor is stimulated by elevated progesterone levels?
TSH receptor –> Thyrotoxicosis
What happens to pulsatility due to progesterone release?
Negative feedback, therefore decrease pulsatile effect of GnRH
What is hypogonadism?
Is concerned with decreased oestrogen and testosterone concentrations within and females respectively –> Associated with reduced gonadal function (Trauma to organs, infections (Mumps))
What is primary hypogonadism in males?
Reduction in testosterone (low E2) secretion from testes, and reduced oestrogen secretion from ovaries. Subsequent reduction in gonad-hormones result in reduced exertion of negative feedback onto the gonadotrophs – increased lH/FSH
Describe the LH/FSH levels for patients with primary hypogonadism?
LH/FSH levels are elevated
During menopause which hormones are at lower concentrations?
E2, oestrogen and inhibin
During menopause which hormones are elevated?
FSH and LH
What are the common causes of primary hypogonadism in males?
Infection
Trauma
Cancer of testes
What is secondary hypogonadism?
Due to hypothalamic and pituitary disorders -> Reduced secretion of FSH & LH from anterior pituitary gonadotrophs
How can a pituitary adenoma lead to secondary hypogonadism?
Elevated production of prolactin, exerts negative inhibition on kisspeptin causing downstream inhibition and pulsatility on GnRH -> Reduced gonadotrophin release –> Low e2 and testosterone, oestrogen
What is menopause?
Oestradiol deficiency
What are 7 main consequences of menopause?
Skin dryness; hair thinning
Hot flushes; sweating; sleep disturbances
Mood disturbance
Osteoporosis: Decreased bone mineral density (BMD); E2 stimulates osteoblasts.
Sexual dysfunction: Vaginal dryness, decreased libido
Weight gain
Amenorrhoea: No periods for 1 year+; cessation of fertility; climacteric: Irregular periods in the years approaching menopause.
What are the treatments for menopause?
Oestrogen replacement –> Hormone replacement therapy
How can hyperplasia cancer be reduced during hormonal therapy?
Oestrogen stimulates the endometrium; combination of progesterone facilitates endometrium maintenance Preventing the risk of endometrial hyperplasia/cancer.
What is the median age for menopause?
51 years
When does gametogenesis occur?
Occurs at puberty (gonadrche)
How long is the spermatogonia pool lifespan?
Poo available for subsequent spermatogenic cycles throughout life generating continuous fertility
What meiotic phase are primary oocytes within primordial follicles halted in?
Prophase 1
What happens to primordial follicles?
Undergo atresia
Which hormone is secreted by Sertoli cells within ovaries can be used to test ovarian reserve?
Anti-Mullerian hormone (AMH)
What happens during pre-menopause?
Premature ovarian failure (POF), conception can happen in 20%
How is premenopausal diagnosed?
Elevated FSH > 2,5iU/L
What are the 3 main causes of pre-menopause?
Autoimmune
Genetic :Fragile X syndrome, Turner’s
Cancer therapy: Radio/chemo therapy
What does the free testosterone hypothesis suggest?
Sex-hormone binding globulin is reduced and becomes unavailable , thus reducing free testosterone availability
Which plasma protein is bioactive testosterone bound to?
Albumin
When is testosterone levels high during the day?
During the morning
When should testosterone levels be measured?
before 11am
What pattern is exhibited by testosterone?
Diurnal rhythm
What are the main symptoms of testosterone deficiency?
Symptoms of deficiency: Sexual dysfunction (Reduced libido); erectile dysfunction (loss of early morning erections); hair growth (frequency of shaving); energy levels; mood disturbances, body composition (Increased fat, reduced muscle mass, gynaecomastia (breast enlargement in males)); spermatogenesis (high levels of intratesticular testosterone required); bone health (Conversion to oestrogen).
Which enzyme converts testosterone into 17B-estradiol?
Aromatase
Which enzyme converts androstenedione to oestrogen?
Aromatase
Which enzyme converts testosterone into DHT?
5-alpha-reductase