PBL 7 - Hormone Problems

Question 1

1) What is the common mode of action of thyroid hormones, cortisol and growth
hormone on glucose metabolism of the liver? [

Answer 1

All 3 hormones activate gluconeogenesis in the liver.

Question 2

Why does the endocrinologist perform an insulin tolerance/stress test? (ii)
What is the test based on and what is the procedure? [

Answer 2

Growth hormone levels are pulsatile and almost undetectable for most of the
day and so growth hormone levels are measured by their response to stimulation
[1 mark]
(ii) Gold standard is insulin-induced hypoglycaemia [1 mark]
Blood is taken for growth hormone, cortisol and glucose and then fast-acting
insulin is injected intravenously. Blood is taken again for growth hormone, cortisol
and glucose after 30, 45, 60, 90 and 120 minutes. [1mark]

Question 3

i) Why is the doctor surprised to see normal levels of TSH? (ii) How could this
be explained? [1 mar

Answer 3

With a low T4, you would expect an elevated TSH (as seen in previous
scenario) [1/2].
(ii) The fact that it is normal indicates that there is pituitary damage (the gland
is not able to produce high levels of T4) [1/2].

Question 4

What is NSILA and which hormone accounts for it? [2

Answer 4

NSILA: nonsuppressible insulin-like activity. [1 mark]

The insulin-like biological effects of IGFs accounts for NSILA [1 mark

Question 5

) Of all the hormonal deficiencies Sarah is suffering from, which one is the most
dangerous and life threatening?

Answer 5

Cortisol deficiency

Question 6

Define bitemporal hemianopia and explain why Sarah had the disorder.

Answer 6

Absence of the outer half of field of vision in both eyes [1]. The enlarged pituitary
gland presses on the optic chiasma – the site at which the two optic nerves cross
over

Question 7

which hormones are released from the AP

Answer 7

LH, FSH
TSH
Prolactin
GH
ACTH

Question 8

Adrenocorticotrophic Hormone (ACTH)

Answer 8

o Coded by POMC + Secreted in response to biological stress
o Stimulates cortisol and androgen release from adrenal gland
o Circadian rhythm – starts to rise at 3am and peaks before waking, lowest in evening

Question 9

Growth hormone

Answer 9

o Stimulates growth, carbohydrate metabolism and cell proliferation
o GH- insulin antagonist – removes excess lipids, lipolysis, gluconeogenesis
o Growth effects due to IGFs produced in liver
o Pulsatile secretion – higher in night and increases in hypoglycaemia

Question 10

Prolactin

Answer 10

o Pulsatile secretion – causes milk production, role in metabolism and immune system
o Dopamine on D2 receptors inhibits release, stress, exercise and pregnancy rise
o High levels inhibit HPG axis as inhibits kisspeptin

Question 11

Thyroid stimulating hormone

Answer 11

o Glycoprotein stimulates thyroid gland to produce thyroxine and triiodothyronine
o TH – increase BMR, protein synthesis

Question 12

LH and FSH

Answer 12

o Produced by gonadotrophs in AP

o Pulsatile secretion and cycle in female–> stimulate gonadal function and produce oestrogen and testosterone

Question 13

Why does she have low cortisol

Answer 13

Low ACTH

Question 14

Effects of low cortisol

Answer 14

Most dangerous so replaced first
o Fatigue, weight loss, vomiting, abdominal pain, low blood sugar, hyperpigmentation
o When acute/rapid – hypovolemic shock – confusion, psychosis

Question 15

Why elevated prolactin

Answer 15

Stalk damage (patient) so dopamine not being delivered from hypothalamus to pituitary which inhibits the prolactin
(STALK EFFECT)
Prolactin inhibits kisspeptin so no GnRH activation

Question 16

Why is TSH normal

Answer 16

o T4 low, expect a high TSH but her TSH is low/normal, hence pituitary damage that does not allow for TSH production
o Low glucose as TH increase gluconeogenesis and glycogenolysis, stimulate gluconeogenesis

Question 17

Low GH symptoms

Answer 17

(Causes low igf-1)
o Maintains normal muscle function, deficiency results in inadequate energy –> fatigue reduced strength and stamina
o Low as only high at night
o Causes High LDL- GH normally removes lipids

Question 18

Loss of LH and FSH symptoms

Answer 18

loss of menstrual periods and Loss of oestrogen – loss of libido

Question 19

How to measure growth hormone

Answer 19

Suppression test

Question 20

GH function

Answer 20

o Promotes lipolysis in adipocytes and removes excess lipids
o Stimulates protein production (counteracts insulin in the blood) to retain electrolytes + needed for brain function
o Lowers glucose uptake by skeletal muscle + increases hepatic gluconeogenesis

Question 21

• Growth hormone deficiency

Answer 21

o Caused by pituitary adenoma

o High LDL, increase CV mortality risk, fatigue

Question 22

GH axis

Answer 22

If stress, circaidian rhythm, hypoglycasemia ==> GHRH from hypothalamus stimulates SS and GH
which inhibits GH release - Negative feedback via SS and IGF-1

GH causes IGF-1 release from liver –> growth

Question 23

ACTH axis

Answer 23

Circaidian, stress, hypoglycaemia –> CRH from ht –> ACTH causes release of cortisol from adrenals

Question 24

Cortisol function

Answer 24

o Stimulate gluconeogenesis
o Mobilise amino acids
o Suppress immune system
o Inhibit uptake by muscles and adipocytes
o Stimulate lipolysis to produce glycerol for glucose production.
o Plays a role in regulation of electrolyte balance in particular sodium and potassium so a deficiency in cortisol –> low sodium and high potassium

Question 25

Absence of cortisol

Answer 25

Hypovolaemic shock –> confusion/psychosis

Question 26

Insulin tolerance test

Answer 26

• Testing for the function of the HPA
• Insulin is injected at the patient’s vein to induce a hypoglycaemic state (< 3.3 mmol/l) which causes the body to release ACTH and GH –> cortisol in response to stress
• These hormones oppose the action of insulin
• Should not be done on the elderly or those with ischaemic heart problems.

Question 27

Treatment for pt

Answer 27

• Transsphenoidal surgery
Cabergoline (dopamine agonist)
Hydrocortisone + HRT

Question 28

• Transsphenoidal surgery

Answer 28

To remove the symptomatic tumour via the nose using an endoscope or microscope

Question 29

Which HRT

Answer 29

Thyroxine
Sex streoids
Oestrogen
Progesterone 
Synthetic GH
•	Give hydrocortisone first then thyroxine a few days later as it can do damage in hypoadrenal states