Adrenal cortex: Hormones, physiology Flashcards Preview

203: The endocrine system > Adrenal cortex: Hormones, physiology > Flashcards

Flashcards in Adrenal cortex: Hormones, physiology Deck (23)
Loading flashcards...
1

Glucocorticoids
- Synthesis
- Control of secretion
- Example

Synthesised by cells of the zona fascicularis
- 17a hydoxylase enzyme
- From cholesterol

Secretion stimulated by:
- Stimulated by ACTH
- Stress
Inhibited by
- Negative feedback

Example
- Cortisol

2

Mineralocorticoids
- Synthesis
- Control of secretion
- Example

Synthesised by cells of the glomerulosa
- 18-hydroxylase
- From cholesterol

Control of secretion
- RAAS control

Example
- Aldosterone

3

Adrenal androgens
- Synthesis
- Control of secretion
- Example

Synthesised by cells of the zone reticularis
- Using 17a-hydroxylase
- From cholesterol

Control of secretion
- regulated by ACTh release

Example
- Testosterone in very small amounts

4

Cortisol and ACTH diurnal variation

Cortisol levels peak after a delay, when there is an increase in ACTH initially
- Due to slow action of hormones

Cortisol and ACTH peak in the early morning.

Cortisol nadir is 2 hrs later than ACTH in the night.
- Negative feedback

5

Cortisol and stress

Stress from injury, trauma, psychological, hypoglycaemia, illness triggers CRH and ACTH release rapidly.
- High ACTH levels amplifies effects of cortisol.

6

Transport of corticosteroids [3]

Not water soluble---> Only 10% free.

75%---> Corticosteroid binding globulin/ transcortin.

15%----> Bound to albumin

7

Transport of corticosteroids in pregnancy

CBG levels increase
- Causes increase in plasma cortisol
- Free cortisol level still stable.

8

Metabolism of steroid hormones

In the liver
- Glucuronidation to make water soluble
- Excreted in via kidney in urine.

9

Action of cortisol at normal levels

Inhibits insulin's action of cellular glucose intake.

Promotes glycogenolysis.

Promotes hepatic gluconeogenesis by increasing amino acid uptake.

Lipolysis and fatty acid mobilisation.
- Potentiates GH and catecholamines.

Causes elation/ sedation.

Vasoconstriction

10

Action of XS cortisol levels

Fatty acid synthesis and deposition at
- Face
- Trunk
- Intrascapular region

Inhibits the uptake of amino acids in the periphery
- Inhibits skeletal muscle protein synthesis.

11

11-beta hydroxysteroid dehydrogenase

Enzyme that converts cortisol into cortisone.
- Does so in aldosterone sensitive tissue as cortisol can bind to mineralocorticoid receptors.

12

Immunological effects of corticosteroids.

Overall---> Suppresses the immune system.
- Allows function, despite injury/illness.

- Suppresses lymphoid tissue---> Reduced production of antibodies.

- Inhibits cellular function of immunological cells.

- Inhibits proteolytic enzymes that act as inflammatory mediators

- Inhibits phospholipase-A2---> inhibits prostaglandins formation.

13

Corticosteroids effects on injury/ Stress

Removes inflammation of injury, but does not help to redeem the underlying cause of injury.
- Inhibits tissue repair

Reduces inflammation reduces oedema
- Allows mobilisation of limbs

Sedation stimulated
- Relieves pain= more mobilisation of limbs.

14

Addison's crisis

Hypoadrenalism
- Very low cortisol levels

Can occur when long-term treatment of corticosteroids is stopped abruptly.
- Cortex stops producing hormones.
- Fatal within 48 hrs.

15

Mineralocorticoid pharmacological uses
- Example

Replacement therapy
- e.g fludrocortisol
- Hypoaldosteronism treatment.
- Addison's disease treatment

Aldosterone not used as it has a short plasma-half life.

NOT used as an immunosuppressant, does not have major immunological effects.

16

Glucocorticoids pharmacological uses
- Examples
- Conditions treated

Replacement therapy
- Addison's disease/ adrenal insufficiency.

Immunosuppressant/ anti-inflammatory
- Asthma
- Arthritis
- Leukaemia
- Allergies

Examples
- Hydrocortisone [cortisol]

17

Adverse effects of glucocorticoids [5]

Impairs wound healing/ tissue repair
- Can make injuries worse.

Inhibits growth in children.
- Inhibits peripheral protein synthesis

Osteoporosis in adults.

Excess cortisol
- Cushing's
- Diabetes [hyperglycaemic properties]

Adrenal cortex atrophy
- Negative feedback of HPA axis.

18

Hydrocortisone
- Drug type
- Mechanism
- Use
- Standard dose

Glucocorticoid
[cortisol]

Mechanism
- Minds to intracellular receptors to influence gene expression
- Causes anti-inflammation and immunosuppression.

Use:
- Hormone replacement therapy: primary adrenal insufficiency
- Thyrotoxic crisis
- Anti-inflammatory
- Anaphylaxis
- Asthma, leukaemia, arthritis, allergies, eczema

Standard dose [replacement therapy]
- 15-20mg

19

Hydrocortisone
- Bioavailability
- Protein binding
- Metabolism
- Half life

Bioavailability: fairly high
- 60-80%

Protein binding: not water soluble
- HIGH

Metabolism
- Hepatic

Half-life
- 1.5hrs.

20

Hydrocortisone
- Adverse effects [3]

Hyperglycaemia

Osteoporosis

Cushing's

21

Mineralocorticoid secretion
- Triggers
- Inhibitors

Majorly influenced by the RAS.
- Production of Angiotensin II triggers secretion

Trigger---> Low BP
- Dehydration
- Haemorrhage

Other stimulators
- Trauma
- Anxiety
- Hyperkalaemia
- Hyponatraemia

Inhibitor
- ANP

22

Mineralocorticoid action

Aldosterone acts on intracellular aldosterone receptors in kidney tubule
- Insertion of Na+ and K+ channels in DT [mainly], CD, PT, ascending loop.

Also acts to reabsorb Na+ in
- colon
- sweat glands
- salivary glands

Increased Na+ in plasma triggers ADH release
- Absorbs water via aquaporins= increase BP

23

Mineralocorticoid transport

50% protein bound