T1 L6 Adrenal cortex - hormones and physiology Flashcards
What male sex hormones are produced by the outer adrenal cortex?
Dehydroepiandrosterone
Androstenedione
Testosterone
Oestradiol
What enzyme is contained in the outer zona glomerulosa?
18-hydroxylase enzyme
What hormone is synthesised by outer zona glomerulosa?
Aldosterone
What hormone is synthesised by middle zona fasciculata?
Cortisol
What hormone is synthesised by inner zona reticularis?
Androgens
What are steroids synthesised from?
Cholesterol from the diet or synthesised within the adrenal gland
Give an example of a glucocorticoid
Cortisol
Give an example of a mineralocorticoid
Aldosterone
When is ACTH secretion at its highest?
Early in the morning
Increased secretion during times of prolonged stress
When is ACTH secretion the lowest?
In the middle of the night
What percentage of cortisol is bound to plasma proteins?
90%
Describe the plasma proteins that cortisol is bound to
Corticosteroid binding globulin (CBG) - 75%
Albumin - 15%
Why is pregnancy associated with an increase in CBG?
It is a compensatory increase in circulating plasma cortisol concentration so the levels remain stable
What converts cortisol to inactive cortisol?
11-B-hydroxysteroid dehydrogenase contained in aldosterone sensitive tissue
How does cortisol elevate blood glucose?
Antagonises effects of insulin. on cellular uptake of glucose
Stimulates glycogenolysis
Stimulates hepatic gluconeogenesis
What actions does cortisol have on metabolism?
Elevates blood glucose
Stimulates lipolysis and mobilisation of fatty acids
Stimulates amino acid uptake in the liver
Inhibits amino acid uptake and protein synthesis in the periphery
What happens if there is excess cortisol?
Fat synthesis and deposition in novel anatomical sites such as the face, trunk and intrascapular region of the shoulders
What is the effect of glucocorticoids on the immune response?
Suppress lymphoid tissue
Reduce antibody production
Inhibit cellular immune system
Stabilise leucocyte membranes and reduce release of proteolytic enzymes
Inhibit phospholipase A2 and reduce synthesis of inflammatory mediators
What happens during an injury?
Pain alerts sufferer to damage Oedema Infiltration by leucocytes Antibodies inactivate foreign proteins Tissue repair enhanced by prostaglandins
How does adrenocortical stress response decrease the inflammatory response?
Removes pain
Decreases immobilisation induced by oedema
Steroid-induced sedation leading to lack of awareness of severity of the situation
Individual can continue to perform despite presence of injury or infection
What is the main role of mineralocorticoids?
Control sodium and potassium
What controls the secretion of aldosterone?
Renin-angiotensin system
What can directly stimulate release of aldosterone?
Trauma
Anxiety
Hyperkalaemia
Hyponatraemia
What inhibits the secretion of aldosterone?
Atrial natriuretic peptide (ANP)
Where does aldosterone have an effect?
Distal tubule of kidney Collecting duct Proximal tubule Ascending loop of Henle Colon Sweat Salivary glands
What are some pharmacological uses of glucocorticoids?
Replacement therapy Immunosuppressive Anti-inflammatory effects Arthritis, asthma or allergies Treatment of proliferative conditions e.g. leukaemia
What are some adverse effects of glucocorticoids?
Steroid usage may suppress wound healing
Exacerbate infections due to their immunosuppressive effects
Long term use in children can inhibit growth
Long term use in adults can cause osteoporosis
Development of DM and other symptoms of Cushing’s syndrome
Suppression of HPA
Menstrual disturbances
What can happen if steroids are stopped abruptly?
Adrenal cortex is unable to secrete endogenous hormones leading to Addisonian crisis which can be fatal
What pharmacological uses does hydrocortisone have?
Hormone replacement therapy
Anti-inflammatory agents
Immunosuppressants
What adverse effects does hydrocortisone have?
Hyperglycaemia
Osteoporosis
Cushing’s syndrome
