The adrenal gland poster Flashcards
(39 cards)
Where is the adrenal gland located?
Retroperitoneal- on the superior aspect of the kidneys.
What two glands can the adrenal gland be divided into?
The medulla and the cortex.
From superficial to deep-name the four layers of the cortex
Connective tissue
Zona glomerulosa
Zona fasciculata
Zona reticularis
What does the zona reticularis secrete and what regulates it?
It secretes adrenal androgens such as DHEA (sex hormones) and is regulated by ACTH.
What does the zona fasciculata secrete and what controls its secretion
It secretes glucocorticoids such as cortisol and is regulated by ACTH.
What does the zona glomerulosa secrete and what is it regulated by?
Secretes mineralocorticoids such as aldosterone.
Regulated by K+
What does the medulla secrete?
Catecholamines such as adrenaline and noradrenaline.
When is aldosterone released?
When there is a fall in NaCl, blood pressure or extracellular fluid volume.
How can the zona glomerulosa secrete more aldosterone?
Stimulus means cell growth occurs releasing more hormone.
What is Conns syndrome?
Primary aldosteronism. An adenoma in the zona glomerulosa resulting in increased aldosterone secretion.
Describe the NaCl, water, potassium, renin and aldosterone levels in Conns syndrome
NaCl in high concentrations because it is being reabsorbed.
Water also in high concentrations.
Pottasium in low concentrations (hypokalaemia)
Renin will be low because it is trying to inhibit the release of aldosterone. Aldosterone will be high.
What is adrenal hyperplasia?
Presents the same as Conns syndrome causing secondary hypertension however it is bilateral.
How would you diagnose someone with Conns syndrome or adrenal hyperplasia?
Renin- Aldosterone ratio.
If it is greater than 750 then need to do a saline suppression test.
Give 4L of saline over two hours. Then record renin and aldosterone levels. Would expect renin to fall and aldosterone to fall. Needs to decrease by 50% to be deemed normal.
Treatment of Conns syndrome and adrenal hyperplasia
Conns syndrome- surgery
Adrenal hyperplasia- can’t remove both glands therefore have to give an aldosterone receptor blocker (spiranolactone)
How is the release of cortisol stimulated?
By ACTH from the anterior pituitary
Describe the regulation of cortisol
The hypothalamus releases corticotrophin releasing hormone (CRH) which stimulates the anterior pituitary to release ACTH. ACTH then stimulates the adrenals to release cortisol.
Stress/illness and diurnal rhythm also stimulate the hypothalamus to release CRH.
The release of cortisol has a negative feedback system which inhibits the release of ACTH from the anterior pituitary and CRH from the hypothalamus.
What are the functions of cortisol?
It increases lipolysis increasing plasma free fatty acids.
It decreases glucose uptake within tissues (except the brain)
Increases gluconeogenesis in the liver.
It also acts on the muscle increasing proteolysis meaning there is an increase in the plasma amino acids.
Why does the body need glucocorticoids?
When the body is stressed these provide it with energy sources from carbs, fats and proteins.
Cortisol also increases the bodies responsiveness to adrenaline therefore preventing shock and helps with circulation.
It is also an anti-inflammatory and immunosuppressive at high levels.
What would you expect from cortisol hyper secretion?
Decreased protein synthesis therefore muscle wasting
Increased lipolysis meaning there is an increase in free fatty acids that become centrally distributed around the body.
Macrophage activity and cytokine production decrease in the body (immunosuppression)
Cardiac output and blood flow increase due to the increased sensitivity to adrenaline
Reduces osteoblast activity in bone and decreases collagen formation.
Symptoms of cortisol hyper secretion
Moon face- due to redistribution of fat Central obesity for the same reason Easy bruising and slow healing Purpura striae Muscle wasting Polyuria and polydipsia due to the increase in plasma glucose levels Osteoporosis Sense of euphoria.
What is Cushings syndrome?
Hypersecretion of cortisol. Many causes- ACTH dependent, ACTH independent or ectopic cancers.
What is ACTH dependent cushings syndrome?
Most commonly -When there is a pituitary adenoma that secretes ACTH. This then stimulates the adrenal glands to secrete cortisol. The ACTH will not be suppressed by negative feedback because there is just too much being released.
What is ACTH independent Cushings syndrome?
Hypersecretion of cortisol from the zona fasciculata. Meaning that ACTH levels will be low but cortisol will still be high.
Could be due to
Adrenal adenoma, adrenal carcinoma or nodular hyperplasia.
Most commonly is adenoma.
Ectopic cancers and cushings syndrome
Ectopic cancers produce ACTH from elsewhere in the body. Means that the adrenal glands are stimulated.
Most commonly cancers in the lung, the thymus or the pancreas.
