The Adrenal Gland Flashcards
Are the kidneys situated in the intra or retroperitoneal space?
Retroperitoneal
Into where does the right adrenal drain?
Right adrenal vein drains direct into the IVC
Into where does the left adrenal drain?
The left adrenal vein drains into the left renal vein
Which hormones are synthesised by the adrenal medulla?
Catecholamines - epinephrine (adrenaline), norepinephrine, dopamine
What hormones are synthesised by the adrenal cortex?
3 classes of steroid hormone;
- Mineralocorticoids e.g. ALDOSTERONE - involved in Na and K regulation
- Glucocorticoids e.g. CORTISOL: involved in maintaining plasma glucose
- Sex steroids e.g. testosterone
Is it the adrenal medulla or cortex that is the true endocrine gland?
The cortex
What are the three zones of the adrenal medulla, form innermost to outermost? What hormones are produced by each layer?
Zona glomerulosa - Aldosterone
Zona fasiculata - Glucocorticoids
Zona reticularis - Sex hormones
Adrenal Medulla - Catecholamines
From what are al steroid hormones derived?
Cholesterol
What are the tow main products of he adrenal cortex? In which two layers are they produced?
Cortisol - in the zona fasiculata
and aldosterone - in the zona glomerulosa
Defects in which enzyme can often cause congenital adrenal hyperplasia? What is the result of this abnormality?
21-hydroxylase
Results in a deficiency pf aldosterone and cortisol and resulting dysfunction of salt and glucose balance
How is adrenal cortex activity modulated?
Via a long feedback loop on the hypothalamus which regulates CRH release and consequently ACTH release
Why would a 21-hydroxylase deficiency cause adrenal hyperplasia if it is causing hormones not to be produced?
The lack of 21-hydroxylase reduces the cortisol release and therefore removes this link from the negative feedback loop that is necessary for regulating the hypothalamus’ release of CRH. When this inhibition is not present, the hypothalamus increases CRH production which then causes increase ACTH release from the pituitary and activation of the adrenal cortex, causing hyperplasia even though the correct hormones are deficient
What type of hormone is cortisol?
A glucocorticoid hormone (influences glucose metabolism)
Is cortisol soluble in the plasma? Why?
No, it is a steroid hormone
What is relevant about glucocorticoid receptors?
They are found in EVERY nucleated cell
What is the effect of cortisol in terms of the cell function?
It either switches on or off the synthesis of new proteins
Describe the classical pattern of cortisol release
There is a marked circadian rhythm, preceded by a similar release of ACTH. The cortisol burst persists longer than the ACTH because it has a much longer half life - peptide hormones not bound to plasma proteins and therefore easier to remove. It peaks 6-9am and is lowest at midnight.
What is the result of a loss of cortisol?
An inability to deal with stress, particularly in terms of maintaining BG. Complete loss of cortisol results in death
Cortisol is crucial to protect the brain from hypoglycaemia
What is the relationship between glucagon and cortisol?
Cortisol has a permissive effect on glucagon, which alone is not enough to deal with hypoglycaemic challenge and cannot protect the brain from damage
What are the three glucocorticoid actions of cortisol?
Gluconeogenesis - enhances glucose production
Proteolysis - stimulates muscle breakdown = creates gluconeogenic substrates for the liver
Lipolysis - stimulates fat breakdown = FFA in the plasma to provide alternative food source so that BG can be preserved
What are the four non-glucocorticoid actions of cortisol?
- Negative effect on Ca2+ balance - less reabsorption in gut, more excretion at kidney
- Impairment of mood and function - hypercortisolaemia = depression and impaired cognitive function
- Permissive effect on norepinephrine - particularly vascular smooth muscle = HTN
- Suppression of the immune system - reduces circulating lymphocyte count, antibody formation and inhibits inflammatory response
What effect of high cortisol can be seen in the skin and muscle?
Cortisol will protect the brain from hypoglycaemia at all costs, and therefore its actions of lipolysis and proteolysis may result in muscle wastage and skin thinning and becoming more fragile
What type of hormone is aldosterone? Where is it produced?
Mineralocorticoid
The zona glomerulosa of the adrenal cortex
What is its main action?
On the distal tubule of the kidney determining the levels of minerals reabsorbed/excreted. It promotes Na in and K out
What controls the release of aldosterone?
Secretion from the adrenal cortex is primarily controlled by a complex reflex pathway originating in the kidney - the renin-angiotensin-aldosterone system (RAAS)
What is the effect of increased aldosterone?
Simulates Na and H20 retention and K depletion, resulting in increased BP
What is the result of decreased aldosterone?
Leads to Na and H20 loss, and K retention, which = decreased BP
What is a significant disease which is associated with hypersecretion of cortisol? How else can hypercortisolism be caused?
Cushing’s syndrome/disease
Too much cortisol administered therapeutically
What significant disease is associated with hypo secretion of cortisol?
Addison’s disease - hypo secretion of all adrenal steroid hormones due to autoimmune destruction of the adrenal cortex
Describe the adrenal medulla
A modified sympathetic ganglion that is not true endocrine tissue, it is similar to the posterior pituitary in having a neuroendocrine function
What is pheochromocytoma?
A rare endocrine tumour found in the adrenal medulla with results in excess catecholamines = increased HR , increased CO and increased BP
Responds well to surgery
