Endocrine Signalling 3 Flashcards
Whats the difference between autocrine and paracrine
Autocrine is to the same cell type and paracrine - different cell type
What is a pheromone
Substance that goes into the environment (smells etc)
Are there any human pheromones
No robust evidence but believed to be - androstenone
What steroid hormones are produced by the gonads
Oestrogens
Androgens (testosterone, DHT etc)
Progesterone
What non-steroid hormones are produced by the gonads
Inhibin A and B
Activin
Follistatin
(Growth factors)
What hormone is released by the hypothalamus
GnRH
What hormone is produced by the anterior pituitary gland
LH
FSH
Prolactin
What hormone is produced by the pineal gland
Melatonin
What hormones does the placenta produce
hCG
Placental lactogen
How are hormones modulated and why
Via desulphation and glucuronidation - allows them to cross the cell membrane.
Give some methods of hormone modulation
Sulphation
Glucuronidation
Sex hormone binding globulin
AFP
Serum albumin
Glycosylation
Active transport
Biotransformation in the liver
Explain the hypothalamo-pituitary gonad axis for sex hormones
Hypothalamus releases GnRH to AP
AP releases LSH and FH to gonads
Gonads release testosterone, progesterone and oestrogen to target tissues
What is an ultrashort feedback loop
Hormones affect cells which secrete them (autocrine)
What is a short feedback loop
Releasing hormones (e.g. GHRH on the hypothalamus)
What is a long feedback loop
Feedback via the peripheral blood supply (e.g. - GnRH inhibited by sex hormones)
What is photoperiod
The change in environment light cycles
What hormone is affected by photoperiod
Melatonin - high at night
What are retinal ganglion cells positive for
Melanopsin
What does melanopsin do
Melanopsin –> retino-hypothalamic tract –> pineal gland –> manipulates melatonin release
When do most hormones peak
Night time
Why is photoperiod important in humans regarding sexual activity
The rise in melatonin correlated to a rise in pregnancy - therefore melatonin has link to sexual activity.
What are the three stages of sex determination
Genetic sex - determine by sperm if XX or XY present
Gonadal sex - uterus or testes grow etc
Phenotypic sex - looks male/female
What is SRY
Sex determining region - found on Y chromosome as testosterone pushes testes growth
What are the general stages of sex determination
Bipotential gonad - germ cells migrate to gonadal precursor tissue near kidneys
Primary sexual differentiation - reproductive tissues and brain sex - no surge area in males (labour)
Secondary sexual differentiation - secondary sexual characteristics
Why does guevedoces help us understand DHT
Guevedoces is children in the dominican republic which dont grow penises until puberty as have a deficiency in 5-alpha-reductase (testosterone to DHT)
Boys appear female but get second surge of testosterone in puberty and grow secondary characteristics.
What did the guevedoces help achieve
Finasteride - 5 alpha reductase inhibitors
What does anti-mularian hormone and testosterone do to the mesonephric duct and paramesonephric duct during sexual development (MALES)
Mesonephric duct - becomes wolffian duct and epididymis
Paramesonephric duct degenerates
What does no anti-mularian hormone and no testosterone do to the mesonephric duct and paramesonephric duct during sexual development (FEMALES)
Mesonephric duct degenerates
Paramesonephric duct - oviducts, uterus and cervix
How do XY chromosomes make a male
TDF/SRY on Y chromosome - testes develop –> seritoli cells secrete AMH –> Degeneration of paramesonephric duct and leydig cells differentation –> leydig cells make testosterone and dihydrotestosterone –> male duct system, penis, scrotum and accessory sex glands
How does no Y chromosome make a female
No TDF/SRY –> Ovaries develop and no AMH produced –> paramesonephric duct becomes oviducts, uterus and cervix
What is the masculination programming window
Important time which is testosterone dependenent between 10-12 weeks gestation.
Important for male gonad development
What two conditions are important regarding poor testosterone production
Crpytorchidism
Hypospadius
What three hormones are needed for production of female oocytes
E2
FSH
Inhibin
How many oocytes do females have at week 22 gestation compared to birth
7 million –> 2 million
When is LH needed
Late stages of oocyte development, takes over from FSH
Why might a gene have different hormone response elements
WIDER READING - Pg973 of molecular cell biology krieger et al
Allows versatile control over the rate of transcription of a specific gene
What did melatonin injecctions show in rats regarding sexual activity
WIDER READING - Drago 2000
High injections into the amygdala inhibit sexual performance whilst small doses stimulated sexual activity in rats
What does melatonin do to erections
WIDER READING - Boxkurt et al 2018
Deficiency can cause erectile dysfunction
What is an indicator for the masculinization programming window
WIDER READING - Welsh et al 2014
Anogenital distance - can be indicated for azoospermia, hypospadias and cryptorchidism.
