Adrenal Glands

What is the structure of the adrenal glands?

On top of the kidneys

Adrenal cortex (largest) - surrounds the medulla

• Zona glomerulosa (outer), zona fasciculata (middle), and zona reticularis

Adrenal medulla -

• Secretes adrenaline and noradrenaline - fight or flight

What does the zona glomerulosa secrete?

Mineralcorticoids

• Aldosterone - water retention and controls BP

What is the mechanism of action of mineralcorticoid receptors?

• Binds aldosterone

• Produces transport proteins

What does the zona fasciculata secrete?

Glucocorticoids

• Cortisol - stress response

What is the mechanism of action of glucorticoid receptors?

• Binds to cortisol

• Inhibits COX-2 production

What does the zona reticularis secrete?

Androgens

What are the roles of glucocorticoids?

Controlled by pituitary ACTH

• Intermediary metabolism: carbohydrate, lipid and protein

  • Anabolic effects on liver, catabolic effects on skeletal muscle and adipose tissue

• Permissive actions

  • Required for functioning of sympathoadrenal system

  • Necessary for catecholamine synthesis and uptake and action

• Enable body to respond to stress

What is the HPA axis?

Interaction between hypothalamus, pituitary and adrenal gland. Negative feedback

• H releases CRH

• Stimulates anterior pituitary to release ACTH

• Stimulates adrenal cortex to release cortisol

What do endogenous glucorticoids do?

Permit or help action of other hormones

• Usually when at rest

• Enables body to respond to threats

• Increases availability of glucose - energy

• Increased lipolysis, proteolysis and gluconeoenesis

What are the regulatory actions of glucocorticoids?

• Negative feedback on HPA

• Reduce vasodilation, reduce fluid exudation

• Effect on cells of immune system to reduce inflammatory response and immune response

• Reduces unwanted inflammation

• Reduces body's ability to heal

• Reduces body's ability to respond to infections

Where and how do glucocorticoids act?

In target tissues

• Bind to specific cytoplasmic receptors

• Translocation of bound complex to nucleus

• Bind to steroid response elements on DNA

• Either repress or induce transcription of specific genes (depends on tissue)

• Some actions of take time to develop as they rely on gene transcription

How are androgen released?

Minorly by ACTH

What releases aldosterone?

Angiotensin II