Pituitary Gland

Question 1

what regulates prolactin?

Answer 1

dopamine - inhibitory, the less dopamine, the more prolactin produced

Question 2

what is the hypothalamic stimulus for TSH?

Answer 2

thyrotropin releasing hormone

Question 3

what is the hypothalamic stimulus for FSH and LH?

Answer 3

gonadotropin releasing hormone

Question 4

anterior pituitary produces which 5 types of hormone?

Answer 4

growth hormone prolactin thyrotrophin gonadotrophins corticotropins (LH & FSH)

Question 5

Where are the receptors for these 5 anterior pituitary hormones? 1. growth hormone 2. prolactin 3. thyrotrophin 4. gonadotrophins 5. corticotropins (LH & FSH)

Answer 5

1. muscle tissue, bone 2. mammary glands 3. thyroid gland (in neck) 4. gonads - ovaries and testes 5. adrenal glands above kidneys (like a chinese hat)

Question 6

which scan do we use to look at pituitary gland? eg. in case of a tumour

What might happen if there was a tumour in the pituitary gland in terms of vision?

Answer 6

coronal scans using MRI

It would squash the optic chiasma, making one lose his peripheral vision which patients can be unaware of

large pituitary tumour which has risen up through sella turcica

Question 7

what is it called when we lose our peripheral vision?

Answer 7

bitemporal hemianopia

Question 8

which receptors does growth hormone bind to?

Answer 8

muscle, bone, liver –> intermediate which produces insulin-like growth factor (IGF-1)

Question 9

too much growth hormone causes what exactly…

a) before puberty?
b) as an adult?

Answer 9

gigantism (height)

acromegaly (height doesn’t increase but everything else grows bigger)

Question 10

Symptoms of acromegaly?

Why do adults get acromegaly when they have too much growth hormone instead of gigantism?

Answer 10

• coarsening of facial features
• macroglossia (large tongue), prominent nose
• large jaw - prognathism
• Increased hand and feet size
• sweatiness
• headache

Their epiphyseal plates have fused

Question 11

name the two posterior pituitary hormones

Answer 11

arginine vasopressin (anti-diuretic hormone)

oxytocin

Question 12

what is diuresis?

Answer 12

production of urine

Question 13

what is the main physiological action of vasopressin?

How does it do this?

Answer 13

1. anti-diuretic hormone

stimulation of water reabsorption in the collecting duct

concentrates urine –> less urine

2. stimulates aquaporin (water channel) insertion into collecting duct membrane allowing water to be reabsorbed from tubular lumen of the collecting duct and back into the blood

Question 14

oxytocin causes which physiological functions?

Answer 14

• milk ejection
• uterine contraction during delivery of baby

Question 15

Fill the boxes:

Answer 15

1. Growth hormone releasing hormone (+) , somatostatin (-)
2. dopamine (-)
3. thyrotropin releasing hormone (+)
4. gonadotrophin releasing hormone (+)
5. corticotrophin releasing hormone (+)
6. arginine vasopressin (+)

Question 16

What is the definition of a hormone?

Answer 16

chemical messengers that travel in the blood

Question 17

Which hormones are synthesised in inactive form, travel free in the blood and bind to membrane receptors?

Which hormones are synthesised from cholesterol, travel bound to proteins in the blood and bind intracellular targets?

Answer 17

peptide hormones

steroid hormones

Question 18

How is secretion of anterior pituitary hormones controlled?

Answer 18

by secretion of releasing hormones and inhibitory hormones released from hypothalamus

Question 19

which system connects hypothalamus and anterior pituitary?

Answer 19

hypophysial portal system

Question 20

what is a prohormone?

Answer 20

a hormone that requires further processing ie. cleavage to release active hormone

Question 21

how are peptide hormones stored?

Answer 21

In vesicles ie. they are only released in response to signal - regulatory secretion

Question 22

how are steroid hormones stored?

Answer 22

They are not - they are released immediately after they are made ie. constitutitive secretion

Question 23

how do peptide hormones produce their effect?

Answer 23

bind receptors on cell membrane and transduce signal using 2nd messenger system

Question 24

how do steroid hormones produce their effect?

Answer 24

bind to intracellular targets to change gene expression directly

Question 25

Where is the pituitary gland in relation to the mammillary body, optic chiasm, hypothalamus and sella turcica?

bear in mind this is the inferior view of the brain

Answer 25

anterior and superior to mammillary body

inferior to optic chiasm

inferior to hypothalamus

superior to sella turcica

Question 26

how are hypothalamic regulatory factors transported to the anterior pituitary gland?

what is the median eminence rich in and where is it located?

Answer 26

portal circulation

blood vessels, part of hypothalamus located immediately adjacent to pituitary stalk

Question 27

what happens at the median eminence?

Answer 27

hypothalamic parvocellular neurons terminate on the median eminence and release hypothalamic releasing/ inhibitory factors to capillary plexus in median eminence, which are then carried by portal circulation to anterior pituitary

Question 28

what are the five main types of endocrine cell in the anterior pituitary?

Answer 28

somatotrophs

lactotrophs

corticotrophs

thyrotrophs

gonadotrophs

Question 29

what is special about the hypothalamo-pituitary portal system

Answer 29

fenustrations (leaky)