Lecture 12 The Adrenal Gland Flashcards
Where is the adrenal gland situated
Superior pole of the kidney in the retroperitoneal space and weighs 4g in adults
What are the 2 separate endocrine glands that make up the adrenal glands
Adrenal medulla (25%) Adrenal cortex (75%)
Describe the function of the adrenal medulla
Modified sympathetic ganglion derived from the neural crest tissue.
Secretes catecholamines: epinephrine (adrenaline) also norepinephrine and dopamine
Describe the function of the adrenal cortex
True endocrine gland
Derived from mesoderm
secretes 3 classes of steroid hormones
Mineralocorticoids (salt)- aldosterone: involved in the regulation of Na+ and K+
Glucocorticoids (sweet)- cortisol: involved in maintaining plasma glucose
Androgens (sex)- testosterone
What hormone does Zone glomerulus release
Mineralocorticoids- Aldosterone
What hormone does Zone Fasciculata release
Glucocorticoid- Cortisol
What hormone does Zone Reticularis release
Sex hormones- Androgens
What hormone is needed to make cortisol and aldosterone from cholesterol
21-hydroxylase
All steroid hormones ae defined from__
Cholesterol
Defects in 21-hydroxylase cause what and why?
Congenital adrenal hyperplasia
- Lack of 21-hydroxylase inhibits synthesis of cortisol.
- This removes the negative feedback on ACTH and CRH release
- Increased ACTH secretion is responsible for enlargement of adrenal glands- Androgen biosynthesis is unaffected so accumulating steroid precursors are channelled into excessive adrenal androgen production
- Negative feedback of ACTH on CRH synthesis remains.
95% of plasma cortisol is___
Protein bound
All nucleated cells have what type of receptor
Glucocorticoid receptor
Describe the characteristic pattern of release of cortisol
- Marked circadian rhythm, precede by a similar pattern of release of ACTH
- Cortisol burst persist longer than ACTH burst because the half-life is much longer
Why would removal of adrenal gland lead to death?
Unable to deal with stress (maintaining glucose levels)
Cortisol helps protect brain from hypoglycaemia
Incapable of maintaining ECF volume
Cortisol has a permissive action on what hormone
Glucagon
Name the actions of Cortisol on glucose metabolism
Gluconeogenesis
Proteolysis
Lipolysis
Decreases insulin sensitivity in muscle and adipose tissue
What are the non-glucocorticoid actions of cortisol
Reduce calcium plasma levels
Impair mood and cognition
Permissive effect on norepinephrine
Suppression of the immune system
What are the side effects of glucocorticoid therapy
Muscle wastage
Increases severity and frequency of infection
Loss of percutaneous fat- thinning of skin, more fragile
What organ does aldosterone act on
Distal tube of kidney
What is the action of increased aldosterone
Increases Na+ (H20) retention and excretes K+
Results in high blood volume and raised blood pressure
Secretion of the adrenal cortex is controlled by a complex pathway called
Renin-angiotensin-aldosterone system (RAAS)
What is the action of decreased aldosterone
Decreased absorption of Na+ (H20) and increase in K+ which results in low blood volume and pressure
Hypersecretion of cortisol leads to
Cushing’s disease/syndrome
What conditions can lead to hyper secretion of cortisol
Tumour in adrenal cortex (primary hypercortisolism) or pituitary gland (secondary hypercortisolism)- most common. Excess ACTH
Name a condition that is caused by hypo secretion of cortisol
Addisons Disease
Due to autoimmune destruction of adrenal cortex
How do neurohormones travel from CNS to blood
Preganglionic fibres terminate on specialised postgranglionic cells in the adrenal medulla. The postganglionic fibres do not have axons and the neurohormones are released directltinto the blood
What is Pheochromocytoma
Rare neuroendocrine tumour
in adrenal medulla
Excess catecholamines, increased HR, CO, BP
Diabetogenic due to adrenergic effect on glucose metabolism. Can be resolved with surgery
