Reproductive endocrinology and menstrual cycle

Question 1

General structure of steroids

Answer 1

27 carbon skeleton
four fused rings
small, lipophillic molecules

Question 2

What is the central core molecule of all steroids?

Answer 2

Cholesterol

Question 3

Give 3 examples of steroid hormones

Answer 3

Testosterone
Progesterone
Oestrogens

Question 4

What differentiates different steroid hormones

Answer 4

The functional groups attached to four ring structure

Question 5

3 oestrogens?

Answer 5

Oestrone (E1)
Oestradiol (E2)
Oestriol (E3)

Question 6

Which oestrogen is usually being referred to when oestrogen is mentioned?

Answer 6

Oestradriol

Question 7

Which oestrogen is only seen in pregnancy?

Answer 7

Oestriol (E3)

Question 8

Where is testosterone produced in men and women?

Answer 8

Men: Leydig cells of testes
Women: Thecal cell, adrenals, peripheral conversion in adipose

Question 9

Where is DHT produced in men and women?

Answer 9

Men: conversion from testosterone in sertoli cells
Women: peripheral conversion from testosterone

Question 10

Where is progesterone produced in men and women?

Answer 10

Men: Adrenals
Women: Corpus luteum, synctiotrophoblasts

Question 11

Where is oestradiol produced in men and women?

Answer 11

Men: peripheral conversion from testosterone where aromatase is present
Women: granulosa cells, peripheral conversion from testosterone, syncytiotrophoblasts

Question 12

How are steroids synthesised in men? (6 steps)

Answer 12

• Gonadotrophin releasing hormone stimulates FSH and LH from ant. pituitary
• LH stimulates testosterone produced by Leydig
• Testosterone and pituitary FSH mainly go to sertoli
• Enzyme 5-alpha reductase converts testosterone to DHT
• Sertoli cells secrete androgen binding protein
• Binds to testosterone and carries to seminiferous tubule to stimulate spermatogenesis

Question 13

How are steroids synthesised in females? (4 steps)

Answer 13

• LH stimulates testosterone production by theca cells in ovarian follicle
• Testosterone enters granulosa cells, converted by aromatase to oestrogen
• Oestradiol stimulates formation of LH receptors on granulosa cells
• Enables follicles to respond to LH surge–> ovulation

Question 14

3 functions of progesterone

Answer 14

prepare endometrium for implantation
effects cervix, vagina and breast
placental progesterone maintains endometrium in pregnancy

Question 15

Are steroid hormones of glycoprotein hormones bigger molecules?

Answer 15

Glycoprotein

Question 16

How are structures of FSH, LH, hCG and TSH similar?

Answer 16

Same alpha unit (29 amino acids)

Question 17

How are structures of FSH, LH, hCG and TSH different?

Answer 17

Different beta unit

Question 18

Why are LH and hCG particularly similar?

Answer 18

Same amino acids, stimulate same receptors

hCG has 24 extra amino acids

Question 19

What structure releases gonadotrophin releasing hormone?

Answer 19

The hypothalamus

Question 20

What stimulates release of FSH and LH?

Answer 20

Gonadotrophin releasing hormone

Question 21

What is the effect of FSH on the body?

Answer 21

Stimulates growth of Graafian follicles to maturity

Enhances production of androgen binding protein by sertoli cells of testes

Question 22

What is the effect of LH on the body?

Answer 22

Surge triggers ovulation- converts residual follicle into corpus luteum
Necessary to maintain luteal function
Stimulates thecal cells in ovary to produce testosterone for oestradiol production
Acts upon Leydig cells of testes and produces testosterone (men)

Question 23

Effect of hCG on body?

Answer 23

maintains corpus luteum

Question 24

What is benefit of peptide hormones having a half life?

Answer 24

Means they are fast acting and effect is not long lasting

Question 25

Name 4 peptide hormones

Answer 25

Gonadotrophin releasing hormone
Growth hormone releasing hormone
Oxytocin
Prolactin

Question 26

What are the 3 stages of the menstrual cycle?

Answer 26

Menstrual stage: 1-5 days
Proliferative stage: 6-14 days
Secretory stage: 15-28 days

Question 27

What happens during the menstrual stage?

Answer 27

Endometrium collapses due to lack of oestrogen and progesterone.
Sheds with blood from ruptured arteries
Detached endometrium passes through vagina as menstrual flow

Question 28

What happens during the proliferative stage?

Answer 28

Oestrogen from mature follicle stimulates thickening of endometrium
Glands and spiral arteries form
Oestrogen stimulates synthesis of progesterone receptors on endometrial cells

Question 29

What happens during the secretory stage?

Answer 29

progesterone from corpus luteum acts of endometrium

stimulates enlargment of glands which secrete mucus and glycogen in prep for fertilised oocyte

Question 30

What happens if fertilisation doesn’t occur?

Answer 30

Corpus luteum degenerates and forms corput albicans
Progesterone levels fall
Endometrium breaks down
Menstruation occurs

Question 31

What happens if fertilisation does occur?

Answer 31

Blastrocysts implants into materal endometrium
Developing placenta secretes hCG
Corpus luteum doesn’t degenerate because of hCG

Question 32

Functions of androgens? (6)

Answer 32

Induce male sexual characterstics
Support spermatogenesis
Influence sexual and aggresive behaviour
Promote protein anabolism, somatic growth
Induce body hair
Regulate gonadotrophin secretion

Question 33

What is the most potent androgen?

Answer 33

DHT

Question 34

Functions of oestrogens? (5)

Answer 34

Stimulate growth of mammary gland and endometrium
Induce female secondary sexual characteristics
Prepare uterus for spermatazoa transports
Increase vascular permeability
Regulate secretion of gondotrophin