Reproductive endocriniology

Question 1

what are steroid hormones derived from

Answer 1

enzymatic modification of cholesterol

Question 2

describe the biosynthesis of steroid hormone

Answer 2

Synthesised in a series of reaction pathways from cholesterol
Process occurs mainly in the mitochondria and the smooth ER
Not stored prior to secretion (lipid soluble and permeable to membranes), they are released upon their synthesis
Circulate in blood primarily bound to plasma proteins

Question 3

describe the mechanism of action of steroid hormone

Answer 3

Steroid hormone enters the target cell
Binds to a steroid hormone receptor present in the target cell
The hormone-receptor complex enters the nucleus
Binds to DNA in the nucleus and activates transcription
New mRNA is made which moves to the cytoplasm
Translation produces new proteins

Question 4

Give examples of steroid hormones

Answer 4

cortisol
oestrogen
progesterone

Question 5

explain the location of the hypothalamus and the pituitary gland

Answer 5

PG is in the brain and sits under the hypothalamus (deep structure within the brain), pituitary stock

Question 6

List functions of the hypothalamus

Answer 6

Links the nervous system to the endocrine system
Located below the thalamus
Part of the limbic system
Controls body temperature, hunger, sleep, thirst etc

Question 7

list functions of the pituitary gland

Answer 7

Endocrine gland
Suspended from the underside of the brain by the pituitary stalk
Has an anterior and a posterior portion

Question 8

What hormones does the posterior pituitary gland produce and its functions

Answer 8

ADH- water retention by the kidneys

Oxytocin- milk ejection during lactation

Question 9

What hormones does the anterior pituitary gland produce and its functions

Answer 9

FSH/LH- regulation of gamete production
Growth hormone- stimulates cell proliferation and regulates growth
Thyroid stimulating hormone- stimulates the synthesis and release of thyroid hormones
Prolactin- stimulates milk production during lactation
Adrenocorticotrophic hormone- stimulates cortisol secretion from the adrenal glands

Question 10

what is the 1st level of hormonal control regulated by?

Answer 10

regulated by interactions between the hypothalamic-pituitary-gonadal axis

Question 11

describe the hypothalamic-pituitary-gonadal axis interactions

Answer 11

The hypothalamus secretes gonadotrophin releasing hormone (GnRH) which stimulates the anterior pituitary to release follicle stimulating hormone (FSH) and luteinising hormone (LH)

The ovary or testis (and placenta) respond to levels of the gonadotrophins and secrete steroid sex hormones

Question 12

What is the 2nd level of hormonal control regulated by?

Answer 12

pituitary gland
anterior- secretes LH/FSH and acts on ovary/testes and secretes prolactin
posterior- secretes oxytocin which is involved in lactation and childbirth

Question 13

What is the role of FSH in males and females

Answer 13

Males- Stimulates primary spermatocytes to undergo meiosis. Enhances production of androgen binding protein in Sertoli cells of the testis

Females- Initiates recruitment and supports growth of ovarian follicles (granulosa cells)

Question 14

What is the role of LH in males and females

Answer 14

Males- Acts on the Leydig cells of the testis to regulate production of testosterone

Females- Supports ovarian theca cells
LH surge triggers ovulation

Question 15

What is the 3rd level of hormonal control regulated by?

Answer 15

Gonads (Ovaries, testes (and placenta)

Question 16

What is puberty controlled by

Answer 16

Puberty is controlled by sex steroid hormones and growth hormone

Question 17

what is growth hormones secreted by and examples

Answer 17

anterior pituitary gland

Peptide hormone, non-receptor tyrosine kinase

Question 18

What does growth hormone stimulate

Answer 18

Cell proliferation via IGF-1
Protein synthesis leading to enlargement of tissues
Chrondrocyte proliferation (endochondral bone growth)

Question 19

when does growth stops

Answer 19

Growth stops when the growth plate in long bones is eradicated by fusion of the epiphysis and diaphysis (limbs and back)

Question 20

Describe puberty in females

Answer 20

Adrenal androgens produced from age 7-8
LH and FSH begin to be released sporadically
Results in waves of oestrogen secretion form the ovaries

All result in: Breast development
		Pubic and axillary hair
		Growth spurt
		Change in body shape
		Menarche

Question 21

describe puberty in males

Answer 21

Adrenal androgens around age 7-8
Rising FSH and secretion stimulates the Sertoli cells to start spermatogenesis
Leydig cells of the testis begin to respond to sporadic release of LH resulting in release of testosteron

All result in: Testis enlargement (seminiferous tubules develop)
		Penis growth
		Pubic and axillary hair
		Voice breaks
		Facial hair 
		Growth spurt (later than females)
		Change in body shape

Question 22

What triggers puberty

Answer 22

The hypothalamus begins to release pulses of GnRH (generally at night)
This progressively stimulates the ovary / testis