8. HPA & GH

Question 1

What is the embryological origin of the posterior pituitary?

Answer 1

Neuroectoderm - primitive brain tissue

Question 2

What is the embryological origin of the anterior pituitary?

Answer 2

Oral ectoderm - primitive gut tissue

Question 3

Which bone does the pituitary gland sit within?

Answer 3

Sella turcica

Question 4

Which hormones are produced from the posterior pituitary?

Answer 4

ADH and oxytocin

Question 5

Which hypothalamic nuclei produce ADH and oxytocin?

Answer 5

Supraoptic and paraventricular nuclei

Question 6

Hormones synthesised in the hypothalamus are stored in the ______ ________ before release into the hypophyseal portal system.

Answer 6

Median eminence

Question 7

What type of hormones are released from the hypothalamus to the anterior pituitary?

Answer 7

Tropic hormones - stimulate (or inhibit) endocrine cells in the anterior pituitary

Question 8

What are the 6 tropic hormones produced by the hypothalamus?

Answer 8

TRH
PIH
CRH
GnRH
GHRH
GHIH (somatostatin)

Question 9

Why is the control of prolactin secretion unusual?

Answer 9

It is mainly inhibitory by PIH

Question 10

What is PIH?

Answer 10

Dopamine

Question 11

What are the 6 hormones produced by the anterior pituitary in response to the tropic hormones?

Answer 11

TSH
PRL
ACTH
LH
FSH
GH

Question 12

Which tropic hormones control the release of growth hormone from the anterior pituitary?

Answer 12

GHRH

GHIH (somatostatin)

Question 13

What type of hormone is GH?

Answer 13

Protein

Question 14

How are does GH exert most of it’s effect indirectly?

Answer 14

GH stimulates skeletal muscle and liver to produce IGF’s 1 and 2.

Question 15

What is a major role of GH in childhood and teenage years?

Answer 15

Stimulates long bone growth, once epiphyseal plate closes, stimulates width growth.

Question 16

What effect do IGF’s have on bone?

Answer 16

Stimulate bone and cartilage growth

Question 17

What role does GH and IGFs have in adults?

Answer 17

Maintain muscle and bone mass
Promote healing and tissue repair
Modulate metabolism and body composition

Question 18

How does sleep influence GH secretion?

Answer 18

Surge in GH after onset of deep sleep

REM sleep decreases GH secretion.

Question 19

What conditions cause a rise in GH secretion?

Answer 19

Stress (trauma, fever)
Exercise
Fasting
Decrease in levels of glucose and FA

Question 20

What conditions cause a decrease in GH secretion?

Answer 20

Obesity

Increase in levels of glucose or fatty acid

Question 21

How is GH secretion regulated by long loop negative feedback?

Answer 21

Mediated by IGFs:

• Inhibit release of GHRH and stimulate release of somatostatin from hypothalamus.
• Inhibit release of GH from anterior pituitary

Question 22

How is GH secretion regulated by short loop negative feedback?

Answer 22

GH itself stimulates somatostatin release

Question 23

What is the condition caused by GH deficiency in childhood?

Answer 23

Pituitary dwarfism -proportionate

Question 24

How can pituitary dwarfism be treated?

Answer 24

GH therapy

Question 25

What is the condition caused by GH excess in children?

Answer 25

Gigantism

Question 26

What is the condition caused by GH excess in adults?

Answer 26

Acromegaly

Question 27

What are the signs of acromegaly?

Answer 27

Large extremities - hands, feet, lower jaw

Question 28

What is the most common cause of GH excess?

Answer 28

Pituitary adenoma

Question 29

How does GH exert its effect on cells?

Answer 29

Tyrosine receptor JAK kinases

Question 30

What happens when GH binds to it's tyrosine kinase receptor?

Answer 30

Cross phosphorylation of JAK, phosphorylation of receptor and activation of pathways leading to transcription of IGF.

Question 31

Which IGF is mainly utilised for foetal growth?

Answer 31

IGF 2

Question 32

What response does IGF binding to target cells generate?

Answer 32

Cell growth (hypertrophy) Cell number (hyperplasia) Increase rate of protein synthesis Increase lipolysis

Question 33

How do the actions of IGF and insulin differ?

Answer 33

Insulins effects are mainly metabolic IGF mainly mitogenic There is some cross-activation across receptors, especially at hybrid receptor.

Question 34

What is the hybrid receptor comprised of?

Answer 34

one subunit from the insulin receptor and one subunit from the IGF1 receptor, so binds to both insulin and IGF1.

Question 35

Which disease results from excess growth hormone secretion occuring after puberty after the epiphyseal plates have closed?

Answer 35

Acromegaly

Question 36

Why might a patient with a pituitary adenoma develop visual field loss?

Answer 36

The pituitary is in close proximity to the optic chiasm so growth of the adenoma can compress the optic nerves

Question 37

Which of the following is a symptom of hyperprolactinaemia in women?

Answer 37

Galactorrhoea - milky secretion from breasts

Question 38

Which biochemical finding would you expect in a patient with acromegaly?

Answer 38

Plasma IGF-1 above the normal range

Question 39

What is diabetes insipidus caused by?

Answer 39

Lack of ADH (vasopressin)

Question 40

What is a typical clinical consequence of untreated diabetes insipidus?

Answer 40

Hypernatraemia

Question 41

What is the pattern of cortisol concentration?

Answer 41

Cortisol is at its highest level in the morning and lowest level at midnight.

Question 42

Which type of drug can be used to treat prolactinoma?

Answer 42

Dopamine receptor agonist