gonads

Question 1

steroid hormones in males

Answer 1

mainly androgens (some oestrogens, progesterones)

Question 2

steroid hormones in females

Answer 2

mainly oestrogens and progesterones (some androgens)

Question 3

steroidogenesis of androgens: precursor and location

Answer 3

cholesterol to small amount of androgens in adrenal cortex (zona reticularis) or in gonads (progesterones, androgens and oestrogens)

Question 4

dihydrotestosterone synthesis pathway from androstenedione in testes

Answer 4

androstenedione → 17-OH-progesterone → testosterone → dihydrotestosterone

Question 5

significance of dihydrotestosterone

Answer 5

most potent form responsible for puberty phenotypic appearances

Question 6

17B-oestradiol synthesis pathway from androstenedione

Answer 6

androstenedione → 17-OH-progesterone → oestrone → 17B-oestradiol

Question 7

significance of 17B-oestradiol

Answer 7

most common oestrogen; activated by FSH

Question 8

testosterone transport

Answer 8

lipid-soluble so must be bound to sex hormone binding globulin in blood or androgen binding globulin in seminiferous fluid

Question 9

what % of testosterone is unbound and bioactive

Answer 9

2%

Question 10

2 effects of testosterone in fetus

Answer 10

development of male internal and external genitalia; fetal growth acting with other hormones

Question 11

effects of testosterone in adults

Answer 11

needed for spermatogenesis; growth and development of male genitalia and secondary sex characteristics (e.g. facial hair); protein and bone anabolism (i.e. muscle, bone growth); behavioural (male sexual behaviour); pubertal growth spurt (with GH); some effects mediated by conversion to oestrogen

Question 12

oestrogens definition

Answer 12

any substance which induces mitosis in the endometrium (causing womb to thicken)

Question 13

examples of oestrogens

Answer 13

17B-oestradiol, oestrone (precursor), oestriol

Question 14

17B-oestradiol effects in endometrium

Answer 14

stimulates proliferation (mitosis) causing womb thickening

Question 15

17B-oestradiol effects in menstrual cycle

Answer 15

triggers LH surge resulting in ovulation

Question 16

other 17B-oestradiol reproductive effects

Answer 16

vagina/cervix secretions; stimulation of growth of ductile system in breasts; decrease of sebaceous gland secretions in skin

Question 17

other 17B-oestradiol effects unassociated with reproduction: GnRH, osteoblasts, metabolic actions, behaviour, salt and water reabsorption, plasma protein synthesis, release of other hormones

Answer 17

feedback regulation on GnRH (negative and positive), stimulates osteoblasts, metabolic actions (e.g. on lipids), behavioural effects, increases salt and water reabsorption, increases plasma protein synthesis, influences release of other hormones

Question 18

define progestogens

Answer 18

any substance inducing secretory changes in endometrium

Question 19

examples of progestens

Answer 19

progesterone, 17a-hydroxyprogesterone

Question 20

effects of progestogens: secretory activity in endometrium, GnRH, body basal temperature, renal NaCl reabsorption, alveolar system in breasts

Answer 20

stimulates secretory activity in endometrium and cervix, negative feedback regulation on hypothalamic GnRH, increase body basal temperature, decrease renal NaCl reabsorption, stimulates growth of alveolar system in breast

Question 21

hypothalamo-pituitary-testicular axis

Answer 21

GnRH released from hypothalamus pulse generator → stimulates release of LH and FSH from anterior pituitary → LH stimulates Leydig cells to make testosterone and FSH stimulates Sertoli cells to support spermatogenesis → testosterone feed backs negatively on (direct) anterior pituitary and (indirect) hypothalamus, and Sertoli cells produce inhibin which feeds back negatively on (direct) anterior pituitary and (indirect) hypothalamus

Question 22

what does GnRH stand for

Answer 22

gonadotrophin releasing hormone

Question 23

hypothalamo-pituitary-ovarian axis

Answer 23

GnRH released from hypothalamus pulse generator → stimulates release of LH and FSH from anterior pituitary → LH stimulates ovulation and FSH stimulates 17B-oestradiol and inhibin production → 17B-oestradiol and inhibin feed back negatively on (direct) anterior pituitary and (indirect) hypothalamus