Gonads 2 Flashcards
What is the difference between primary and secondary amenorrhoea?
Primary - never had a period
Secondary - used to have period but then they stopped
Which cells in the testes have receptors for FSH and LH?
Sertoli Cells - FSH Leydig Cells - LH
What are the effects of androgens in adults?
spermatogenesis growth and development protein and bone anabolism ie muscle/bone growth male sexual behaviour growth spurt
What’s the main progestogen?
progesterone
How are some of the androgenic effects mediated?
conversion to oestrogen
Name the weak androgen that is produced both in the adrenal glands and in the testes.
Androstenedione
What is the main oestrogen in pregnancy?
Oestriol
How is testosterone and DHT transported in the blood?
Mainly bound to sex hormone binding globulin (SHBG) Some of it is bound to albumin A small amount is free and bioactive This is in dynamic equilibrium
If fertilisation occurs, high levels of oestrogen and progesterone is needed. What molecule is produced to mimic LH and stimulate further oestrogen and progesterone production?
Human Chorionic Gonadotrophin
Complete sentence…
Rising oestrogen levels has a negative feedback effect on…
FSH
Most developing follicles will then undergo atresia and only one follicle remains, the Graffian follicle. What enables this follicle to survive the negative feedback on FSH?
The Graffian follicle is no longer FSH-dependent and can survive with it’s own local production of oestrogen. The other cells are FSH-dependent and so undergo atresia when the FSH is removed.
How do these pathways cause negative feedback?
Decreases the AMPLITUDE of the GnRH pulses.
Where does the aromatisation of testosterone into oestrogens occur?
adrenals, testes, liver, skin and brain
Describe the local positive feedback loop in the ovaries.
FSH stimulate aromatase and increase conversion of androgens to 17 beta oestradiol. Oestrogen then leaves the granulosa cell and binds to oestrogen receptors on the SAME granulosa cell and further stimulates production of oestrogen.
What hypothalamic hormone stimulates FSH and LH release from the pituitary gland?
Gonadotrophin Releasing Hormone (GnRH)
Define progestogen.
Any molecule that induces secretory changes in the endometrium
Define infertility.
Woman - inability to get pregnant
Man - inability to impregnate
may be due to excess prolactin (due to prolactinoma)
What are the actions of progestogens?
Stimulates secretory activity in the endometrium and cervix Decrease renal NaCl absorption Growth of alveolar system in breast Increase in body temperature Negative feedback reg. on Hypothalamic GnRH
Describe spermatogenesis in testes
Sertoli cells
Stimulated by FSH, limited by inhibin -ve feedback(direct /indirect)
Sperm maturation also NEEDS testosterone
If fertilisation does not occur, what happens?
Oestradiol, Progesterone and Inhibin have negative feedback effect on FSH and LH leading to luteolysis and menstruation.
Define oestrogen.
Any molecule that induces mitosis in the endometrium.
What are the actions of oestrogens?
Stimulate mitosis in the endometrium Causes LH surge resulting in ovulation Feedback regulation of GnRH Stimulates osteoblasts Behavioural effects Metabolic actions (eg lipids) Increased salt and water reabsorption Increase HDL Stimulates growth of ductile system in the breast Decreases sebaceous gland secretion
Describe the negative feedback from the testes to hypothalamo-pituitary axis.
Sertoli Cells - produce INHIBIN - negative feedback effect on hypothalamus and pituitary Leydig Cells - produce TESTOSTERONE - negative feedback effect on hypothalamus and pituitary
