PBL 6: Sarah Taylor

Question 1

What does the pituitary gland release?

Answer 1

Anterior - ACTH, TSH, MSH, LH, GH, FSH, Prolactin

Posterior - Oxytocin & ADH

Question 2

What does ACTH do?

Answer 2

Adrenocorticotrophin hormone
Is responsible for the release of cortisol which is a stress hormone
Corticotrophin releasing hormone controls its release
It is released in hypoglycaemic conditions
It is coded by the POMC genes
Released following circadian rhythms
It is an insulin antagonist
Increased levels = gluconeogenesis in the liver, inhibits glucose uptake in the muscle, increased lipolysis and mobilises amino acids

Question 3

What does GH do?

Answer 3

Growth hormone
Releases IGF-1 which releases somatostatin
Ghrelin and GHRH controls its release
In children it determines height
In adults it determines muscle mass, carbohydrate metabolism, cell proliferation, internal organ growth
Released in a pulsatile way
More is released during the night for women whereas more in the day for men
It is a stress hormone
It is an insulin antagonist = gluconeogenesis in the liver, increased liver glucose uptake, increases lipolysis, controls brain function, increases the HDL:LDL cholesterol ratio, reduces glucose uptake in the muscle, anti-diuretic

Question 4

What does TSH do?

Answer 4

Thyroid stimulating hormone
Produces T4 (thyroxine) which produces active T3 (tri-idothyroxine)
TRH controls its release

Question 5

What do LH and FSH do?

Answer 5

LH produces testosterone
FSH produces oestrogen
GnRH controls their release
Pulsatile release
Responsible for puberty and reproductive function

Question 6

What does prolactin do?

Answer 6

Pulsatile release
Stimulates mammary glands, milk production, metabolism and the immune system
Dopamine inhibits its release by acting on D2 receptors

Question 7

Why are TSH levels normal?

Answer 7

T3 and T4 are low suggesting tat TSH would be low.

However the fact that TSH is normal confirms that there is disruption to the pituitary gland.

Question 8

What are the effects of low ACTH on metabolism?

Answer 8

This is very dangerous and ACTH deficiency is the most fatal deficiency to have out of all the pituitary =hormones.
Can occur gradually or rapidly:
- less severe effects if gradual decline and you get symptoms such as fatigue, weakness, vomiting, weight loss, abdominal pain, hypoglycaemia, hyperpigmentation
- if sudden decline you can get hypovolemic shock, vascular collapse, psychosis, confusion and electrolyte abnormalities

Question 9

What are the effects of low GH on metabolism?

Answer 9

It essentially means there is low IGF-1
Energy levels fall, bone density falls, hyperlipidaemia, impaired cardiac function, miserable mood, brain function may decline, confusion, headaches, blood pressure falls and you become lethargic

Question 10

Why do cholesterol levels increase in GH deficiency?

Answer 10

GH increases the HDL:LDL cholesterol ratio essentially reducing cholesterol levels.
If GH is deficient this ratio falls and you get less LDL cholesterol so cholesterol levels increase.
You can measure this through truncal fat, waist hip ratio and hypertension

Question 11

What is the result of low LH and FSH?

Answer 11

Loss of menstrual periods due to FSH deficiency

This also means oestrogen deficiency so there is loss of libido as well as the vasomotor menopausal symptoms

Question 12

Why were prolactin levels high but there was deficiencies of other hormones?

Answer 12

Due to a pituitary stalk lesion because the adenoma was pushing against it on its enlargement

Question 13

What can cause high levels of prolactin?

Answer 13

Pituitary stalk lesion, pregnancy, stress, exercise, anti-psychotics

Question 14

What are the effects of high prolactin levels?

Answer 14

Inhibition of kisspeptin inhibiting the hypothalamo pituitary - gonadal axis

Question 15

What does a prolactin level of over 2000 mean?

Answer 15

Indicates prolactin secreting tumour

Question 16

What are the main methods of pituitary adenoma management?

Answer 16

1) HYDROCORTISONE (as ACTH deficiency is very dangerous, need to 2-3 tablets a days

THEN

• fix visual defects (transphenoidal hypophysectomy)
• fix pituitary apoplexy (bleeding) through surgery
• external beam radiotherapy (prevents recurrence but may get hypopituitarism
• hormone treatment

Question 17

What is Transphenoidal Hypophysectomy?

Answer 17

surgical procedure most commonly used to remove a tumour of the pituitary gland
Transsphenoidal means through the sphenoid sinus

Question 18

What does hormone treatment involve?

Answer 18

• thyroxine (1 tablet a day, control cortisol first)
• oestrogen (for bones, menstruation, uterine health, libido)
• synthetic GH (daily injection)
• progesterone

Question 19

What is the insulin tolerance/stress test?

Answer 19

• Inject insulin into the vein to induce hypoglycaemia
• induces stress hormones to be released so they can be measured and you can test the hypothalamic pituitary adrenal and growth axis as well as the adrenal capacity
• glucose levels should rise so will not remain being hypoglycaemic
• it is very dangerous

Question 20

In what circumstances would you not carry out a insulin tolerance/stress test?

Answer 20

If cortisol is low
Thyroid hormones are low
Heart disease
MI
Stroke
Epilepsy

Question 21

What is the severity of each pituitary hormone deficiency?

Answer 21

(most dangerous)
Prolactin
ACTH
TSH
FSH
LH
GH
(least dangerous)

Question 22

Why can’t you just measure ACTH and GH levels normally?

Answer 22

At such a low basal level normally but insulin stress test causes a spike so easier to measure