9. Endocrine infertility Flashcards
(34 cards)
what secretes gonadotrophin releasing hormone?
the hypothalamus
what does the secretion of GnRH stimulate?
the release of gonadotrophins (LH&FSH) from the anterior pituitary which (in men) stimulates testosterone release from the testes
what are the 3 phases of menstruation?
- follicular phase
- ovulation
- luteal phase
describe the follicular phase of menstruation
- stimulation of oestradiol release from ovaries (via LH&FSH)
- as oestradiol levels rise, it induces +ve feedback at the hypothalamus
- increase in GnRH and a big LH surge (vital for ovulation)
describe the luteal phase of menstruation
- if implantation does not occur the endometrium is shed (energy consuming)
- menstrual shedding needs to occur otherwise the excessive growth of the endometrium could cause cancer
- if implantation does occur -> pregnancy
what is infertility defined as and what proportion of couples is it a problem for?
inability to conceive after 1yr of regular unprotected sex
1:6 couples
what is primary gonadal failure?
when the ovaries and testes are not working
- if testes aren’t working there is low testosterone -> less -ve feedback -> increased LH/FSH
- if ovaries aren’t working there is less oestradiol -> increased LH/FSH
what is secondary gonadal failure?
when the hypothalamus or pituitary gland isnt working
- problem with the hypothalamus/pituitary -> LH&FSH will be low
- testosterone and oestradiol will be low
what does high FSH&LH but low testosterone/oestradiol suggest?
primary gonadal failure
what does low FSH&LH and low testosterone/oestradiol suggest?
secondary gonadal failure
what are the clinical features of male hypogonadism?
- loss of libido (sexual interest)
- impotence
- small testes
- decreased muscle bulk (testosterone is often used in anabolic steroids)
- osteoporosis (testosterone is involved in bone strength)
what are the 4 main causes of male hypogonadism?
- hypothalamic-pituitary disease
- hypopituitarism
- kallman’s syndrome
- illness/underweight - primary gonadal disease
- congential: klinefelter’s syndrome (XXY)
- acquired: testicular torsion, chemotherapy - hyperprolactinaemia
- androgen receptor deficiency
describe kallman’s syndrome
GnRH neurones don’t migrate and develop properly -> no GnRH released so patient can’t undergo puberty
anosmia (lack of smell)
undescended testes
low-normal stature
what causes anosmia in Kallman’s syndrome?
GnRH neurones and olfactory neurones migrate together in embryogenesis from the base of the brain upwards
how can male hypogonadism be investigated?
- check LH, FSH and testosterone (if all low suggests secondary failure) -> MRI pituitary
- check prolactin (high prolactin switches off gonadal axis)
- check sperm count:
azoospermia - 0 sperm
oligospermia - less sperm - check appearance and motility of sperm
- chromosomal analysis (e.g. for klinefelter’s)
how is male hypogonadism treated?
- replacement testosterone (tablets, injections) to increase muscle bulk and protect against osteoporosis
- subcutaneous gonadotrophin injections to induce spermatogenesis for fertility
- dopamine agonist if the patient suffers from hyperprolactinaemia
what are the endogenous sites of androgen production?
- interstitial leydig cells of the testes
- adrenal cortex
- ovaries
- placenta
- tumours
what are the main actions of testosterone?
- development of the male genital tract
- maintain fertility in adulthood
- control of secondary sexual characteristics
- anabolic effects (muscle, bone)
what are the 2 enzymes involved in the conversion of testosterone and what do they convert testosterone to?
5𝛼-reductase converts testosterone into the active form dihydrotestosterone (DHT) which binds to androgen receptors
aromatase (found in brain and adipose tissue) converts testosterone to 17𝛽-oestradiol which binds to oestrogen receptors
what will testosterone increase in adulthood?
- lean body mass
- muscle size and strength
- bone formation and bone mass
- libido and potency
what are the 3 disorders in the female?
- amenorrhoea
- polycystic ovarian syndrome (PCOS)
- hyperprolactinaemia
what are the different types of amenorrhoea?
primary amenorrhoea - failure to develop spontaneous menstruation by 16yo
secondary amenorrhoea - absence of menstruation for 3 months in a women who previously had cycles
oligomenorrhoea - irregular long cycles
what are the causes of amenorrhoea?
- pregnancy
- lactation (high prolactin stops menstruation)
- ovarian failure: early menopause, ovariectomy, chemotherapy, ovarian dysgenesis (turner’s syndrome)
- gonadotrophin failure: hypothalamic/pituitary disease, kallman’s syndrome, low BMI, post-pill amenorrhoea, hyperprolactinaemia, androgen XS
what are the signs of turner’s syndrome
- short stature
- cubitis valgus (forearm angled away from body)
- gonadal dysgenesis (defective development)
