3.1.3 Adrenal Cortex Physiology Flashcards
What is the objective of this lecture?
Steroidogenesis
What protein is important in the transport of cholesterol into the mitochondria?
Steroidogenic acute regulatory protein (StAR)
Where is CBG synthesized?
Liver
The fasiculata and reticularis express what protein and are responsible for the synthesis of what?
Express CYP17
Responsible for DHEA and cortisol production
Has a role in adrenarche
What are the secretion rates and plasma concentrations of andrenocortical hormones?
Cortisol binding globulin (CBG) binds to what?
Glucocorticoids, aldosterone and progesterone
What are the 3 mechanisms by which hormones are inactivated?
What is the pathway by which 21-hydroxylase deficiency will lead to elevated androgens?
This will also lead to no feedback on ACTH by cortisol
The glomerulosa in the adrenal cortex expresses what?
Aldosterone synthase
What is cortisol’s function in metabolism?
What is cortisol’s function in inflammation and circulation?
What are two tests that can assess adrenal function?
What is Cushing’s Disease?
This is a hypersecretion of ACTH from a pituitary adenoma
The glomerulosa lacks what enzyme?
CYP17
What are the important anatomical parts of the adrenal gland?
How is aldosterone regulated?
What does epinephrine do?
Come on you know this
What genetic defects could lead to adrenal disorders?
What are the effects excess cortisol in metabolism?
What is the treatment of glucocorticoid excess?
Pituitary surgery or remove exogeneous ACTH
Adrenalectomy
Administration of glucocorticoids
What are the main products of the adrenal gland?
Focus on squarred ones
How do serum concentrations of ACTH change throughout the day?
What is the rhythm and peak of cortisol secretion?
ACTH secretion is episodic and has a circadian rhythm (peaks in the morning). Cortisol exerts a negative feedback on the CRH-ACTH system.
Describe the regulation of glucocorticoid and androgen synthesis.
What are the functions of cortisol?
All steroids are derived from?
Cholesterol
Albumin binds to?
glucocorticoids
What is Addison’s disease?
Primary hypoadrenalism
Primary hypofunction (Addison’s disease) of the adrenal gland can be caused by autoimmune disease, destruction of the gland by tuberculosis, or an unknown origin
Cortisol binds to?
CBG and albumin
Describe the renin-angiotensin and it’s role on the adrenals.
What are two sources of steroids?
Diet and de novo
What is Cushing’s syndrome?
Hypersecretion of ATCH from non-pituitary tumor
The glomerulosa is important in the production of what?
Aldosterone
The glomerulosa layer of the adrenal gland is primarily regulated by? (Creepy endocrine guy slide)
Renin/angiotensin (Na+ levels)
also responsive to K+ and ACTH
What is the reaction that is stimulated in the adrenal medulla by ACTH?
Tyrosine ⇒ DOPA
via tyrosine hydroxylase
What are the different layers of the adrenal
Adrenal Cortical layers
1) Zona glomerulosa - This is the outer most layer of the cortex. It is composed of small clumps of cells that synthesize and secrete the mineralocorticoid - aldosterone. These cells are distinct from the underlying layers in that they lack the steroidogenic enzyme P450c17 (17a hydroxylase and 17,20 desmolase), but uniquely express the aldosterone synthase enzyme complex. This explains why aldosterone is only produced within this layer of the adrenal cortex.
2) Zona fasciculata - This layer lies just underneath the glomerulosa.
3) Zona reticularis - This layer lies just underneath the fasciculata.
Both the fasciculata and reticularis layers of the adrenal have the 17a hydroxylase and 17,20 desmolase enzymes and produce glucocorticoids (cortisol and lesser amounts of corticosterone) and androgens (primarily dehydroepiandrosterone).
What is the primary function of the adrenals?
The primary function of the adrenal glands is to protect the organism against acute and chronic stress
What is the rate limiting step in steroid synth?
The initial step in this enzymatic cascade is the rate limiting step: conversion of cholesterol to pregnenolone by P450 side chain cleavage enzyme
and
Transport of cholesterol into the mitochondria
What is a dexamethasone test?
Measurement of glucocorticoids following administration of dexamethasone the night before.
This can detect an ectopic source of ACTH
The fasiculata and reticularis layers of the adrenal cortex lack expression of what?
Aldosterone synthase
What type of effect does ACTH have on fasciculata and reticularis and what can occur in the absence of ACTH?
What are the symptoms of glucocorticoid excess?
Glucocorticoid deficiency can lead to what symptoms?
What is this an image of and what are the characteristics?
EM of cells within the zona fasiculata - characterized by abundant mitochondria, lipid droplets, and smooth endoplasmic reticulum
What is the role of ACTH on the adrenal cortex?
ACTH stimulates the growth of the adrenal cortex especially the machinery necessary for glucocorticoid and androgen biosynthesis. ACTH’s actions at the adrenal cortex are mediated by cyclic AMP. Secondary actions of ACTH include: stimulation of lipolysis, stimulation of insulin secretion, and increased skin pigmentation (often a pathological sign). The secondary actions of ACTH are largely related to the structural homologies of ACTH with the other proopiomelanocortin peptides.
Cortisol induces what reaction in the adrenal medulla?
Norepi ⇒ Epi
Cortisol activated the enzyme that catalyzes the reaction (PNMT)
