Biochemistry Pituitary and Adrenal Flashcards Preview

Cardio > Biochemistry Pituitary and Adrenal > Flashcards

Flashcards in Biochemistry Pituitary and Adrenal Deck (64)
Loading flashcards...
1

Conditions with Increased ACTH (low cortisol/ increase primary production) also present with:

1. Beta endorphins
2. Melanocyte hormone (increased pigmentation)

Cleaved from: pro-opiocortin

2

From Cholesterol produces:

1. Aldosterone
2. Cortisol
3. Testosterone (25%)
4. Oestradiol

3

cortisol Epi production rate

Most important glucocorticoid
Production rate c. 25mg/day

4

Cortisol forms

90% protein bound (CBG and Albumin)
Free Fraction physiologically active

5

Cortisol Effects

Carbohydrate metabolism
• Insulin antagonist
• Gluconeogenesis
Protein Catabolism
Immunosuppression (can be done therapeutic)
“Permissive action”
• Catecholamines
• Free water clearance – w/o cortisol inappropriate ADH production there H2O retention - hyponatraemia

6

Test for Cortisol

Total Cortisol level e.g. bound and free

7

Pathology of Cortisol

Significant abnormalities in proteins such as loss of proteins or an increase in proteins (pregnancy)

8

Increase production of Cortisol

Increase in total and increase in free fraction as binding proteins saturated.

9

Cortisol control

• Negative feedback
• Diurnal (lowest at midnight, rise am, decreases in day)
• Stress (exercise, emotion)

10

Primary Causes of Cortisol suppression:

• Congenital adrenal hyperplasia
• Enzyme defect
• Selective or total destruction via a variety of causes

11

Selective destruction of cortex causes

Autoantibodies

12

Total adrenal destruction cause

Bacterial and fungal infections
TB
Metastatic carcinoma
Amyloidosis

13

Secondary Adrenal Insufficiency causes

Steroids – ACTH deficiency due to hypothalamic or pituitary disease

14

Adrenal Insufficiency Consequences:

1. Hypoglycaemia
2. Hypo-natraemia
3. Hyperkalaemia
4. Hypotension
5. Pigmentation
6. Non-Specific

15

1. Hypoglycaemia

Uncommon seen in neonates/cause adrenal crisis

16

2. Hypo-natraemia

Destruction leads to aldosterone loss and so Sodium loss and…

17

3. Hyperkalaemia

Potassium retention from aldosterone

18

4. Hypotension

Primary Cause (lack of negative feedback = ADH inappropriate control

19

5. Pigmentation

Primary Causes – due to cleavage to form ACTH and so melanocyte hormone produced

20

Addison’s Disease symptoms:

• Lethargy
• Anorexia
• Pigmentation of hands and mouth – look at non sun-exposed areas.
• Abdominal pain
• Weight loss

21

Acute Adrenal Crisis:

• Vomiting
• Nausea
• Dehydration

22

Laboratory Investigations available →

Serum Cortisol
Dynamic synacthen (synthetic ACTH) stimulation test
ACTH

23

Serum Cortisol

Problems as
1. A strong diurnal rhythm
2. If the patient is stressed false raised

24

Dynamic synacthen (synthetic ACTH) stimulation test

Short: 250 ug given IM
Looking for: Rise on cortisol
Normal’s:
• Incremental rise >200 nmol/L
• Absolute rise >600 nmol/L

25

ACTH

Differentiates 1o/20

26

Synacthen stimulation test:

1. Normal rise (+200) and exceeds 600
2. Flat basal, no increase aove +600 – abnormal
3. Baseline normal, response abnormal – poor increase
4. V. high – severe stress
5. V. high – Iatrogenic (hydrocortisone)

27

Causes of poor increase

a. Early stages w/ reserved adrenal function
b. Patient on steroids recently

28

• Primary adrenal failure

lack aldosterone (cortisol) >Na loss and K secretion

29

Electrolytes failure

• >Hyponatraemia >low plasma osmolality >reduced ADH (not completey reduced) – as cortisol permissive

• Loss of water to correct hyponatraemia
• Salt loss continuous and therefore water loss will be as well
• IV V becomes depleted ADH will eventually be secreted and some reabsorption

30

Electrolytes in adrenal failure

• Hyponatraemia, hyperkalaemia, volume depletion

Decks in Cardio Class (108):