Adrenal cortex Flashcards
outline the anatomy and function of the adrenal cortex
inner adrenal medulla secretes catecholamines, concerned with stress response,sodium + glucose homeostasis.
outer adrenal cortex secretes adrenal sex steroids -progesterone, testosterone + oestrogens.
what are the functions of the three distinct layers of the adrenal cortex?
Outer zona glomerulosa (mineralocorticoid e.g. aldosterone synthesis).
Middle zona fasciculata (glucocorticoids e.g. hydrocortisone/cortisol).
Innermost zona reticularis (produces androgen precursors).
what are the major secretions of the adrenal cortex and what are their functions?
Glucocorticoids (e.g. hydrocortisone/cortisol)affect carbohydrate and protein metabolism and regulate host defence mechanisms.
Mineralocorticoids (e.g. aldosterone) regulate water and electrolyte balance.
how does mineralocorticoid sensitive tissues (e.g. kidney) prevent responding to hydrocortisone?
11-β-hydroxysteroid dehydrogenase converts hydrocortisone to the inactive metabolite cortisone
what are the effects of glucocorticoids on the cardiovascular system?
reduced vasodilation and decreased fluid exudation
what are the negative effects of glucocorticoids on the musculoskeletal system?
decreased osteoblast and increased osteoclast activity
what is the effect of glucocorticoids on inflammation and immunity?
anti-inflammatory. allows infection to continue whilst masked.
how are glucocorticoids synthesised and released?
synthesised under the influence of ACTH from anterior pituitary, released in a pulsatile fashion. ACTH secretion is regulated by CRH release from hypothalamus and by ADH release from posterior pituitary. high glucocorticoid concentration in blood prevents release of ACTH and CRH.
how can hyperglycaemia arise due to the metabolic actions of glucocorticoids?
carbohydrates: decreased uptake and utilisation of glucose accompanied by increased gluconeogenesis
how can muscle wastage arise due to the metabolic actions of glucocorticoids?
increased catabolism; reduced anabolism
When are the effects of cortisol rapid?
feedback inhibition of ACTH secretion
Cortisol opposes which hormone?
Insulin. antagonises effect of insulin on cellular uptake of glucose. stimulates glycogenolysis and hepatic gluconeogenesis.
How does cortisol effect lipolysis?
stimulates lipolysis and mobilisation of fatty acids, partially by potentiating the effects of growth hormone and catecholamines.
How does cortisol effect the periphery?
inhibits aminoacid uptake and protein synthesis,resulting in a net loss of skeletalprotein.
What leads to a rapid secretion of ACTH and corticosteroids?
psychological and physiological stress e.g. trauma, infection, hypoglycaemia
What are the unwanted effects of glucocorticoids?
suppression of response to infection or injury, Cushing’s syndrome, osteoporosis, hyperglycaemia can precipitate diabetes, muscle wasting and weakness, inhibition of growth in children.
What are the causes of Cushing’s syndrome?
excessive exposure to glucocorticoids: ACTH secreting tumour or prolonged administration of glucocorticoid drugs (iatrogenic).
What are the most adverse effects of excess glucocorticoids?
suppression of HPA axis and ACTH secretion leading to atrophy of the adrenal cortex.
What is the most important role of glucocorticoids?
responding to stress. at times of prolonged stress glucocorticoidsmaintain enhanced supply of glucosebut they also suppress theinflammatory response.
How does the adrenocortical stress response influence the inflammatory response?
removes pain and decreases the immobilisation induced by oedema.
steroid-induced sedation causes a lower perceived severity of the situation.
so individual can perform despite presence of injury or infection.
What is Addison’s disease and what is it characterised by?
low cortisol production.
muscular weakness, low blood pressure, depression, anorexia, loss of weight and hypoglycaemia.
What are the causes of Addison’s disease?
stopping steroid therapy abruptly (Addisonian crisis), autoimmune, or destruction of the gland by chronic inflammatory conditions e.g. tuberculosis.
What are the pharmacological uses of glucocorticoids?
replacement therapy and for their immunosuppressive or anti-inflammatory effects e.g. in arthritis, asthma or allergies, or for the treatment of proliferative conditions e.g. leukaemia.
What directly stimulates and inhibits the secretion of aldosterone?
trauma,anxiety, hyperkalaemia andhyponatraemia.
inhibited byANP
What is the action of aldosterone?
sodium reabsorption in distal tubule of kidney. influences plasma sodium concentration, which in turn influences water reabsorption in collecting duct via an effect on ADH secretion.
What are mineralocorticoids only used for?
replacement therapy
What is the use, action and adverse effects of hydrocortisone?
hormone replacement therapy as anti-inflammatory agents and immunosuppressants.
acts via specific intracellular glucocorticoid receptors to influence gene expression.
hyperglycaemia, osteoporosis, Cushing’s syndrome
