BMS2031 Lecture Notes - Lecture 16: Glycerol, Androstenedione, Hypothyroidism
31 May 2018
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Week 6. Endocrinology 3&4 Adrenal gland and
control of stress and Growth and calcium regulation
ADRENAL GLAND AND CONTROL OF STRESS
• The adrenal gland is located on top of the kidneys
• Are essential for life
• Controlled by ACTH (adrenocorticotropic hormone) and CRH (corticotropin releasing hormone
form the PVN) from the hypothalamus
• Adrenal gland has two parts:
o Cortex: produces steroids
o Medulla: produces catecholamine (adrenaline and noradrenaline)
• Adrenal medulla:
o Derived from neural tissue
o Part of the ANS
o Releases adrenaline in response to sympathetic stimulation
o Chromaffin cells store adrenaline (80%) and noradrenaline (20%) so that response is
instantaneous
• Adrenaline:
o Acts on adrenergic (G protein coupled receptors) receptors that increase cAMP or IP3
o Mediates fight/flight response
o Has a number of action
o Released from adrenal medulla
o Increases breathing rate
o Relax intestinal muscles
o Pupils dilate
o Increase BP and HR
o Increase blood flow to skeletal muscles
o Increases blood sugar levels
o Hyperadrenalism = Cushig’s sydroe
o Produced from tyrosine
• Two main categories of adrenergic receptors: a and B
• Adrenal medulla = adrenaline
• Adrenal cortex = aldosterone, androgens
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• Adrenal cortex:
o Deficiency leads to fatigue, hypotension and skin pigmentation
o Produces steroid hormones which are all derived from pregnenolone which has
cholesterol as its substrate
o Steroid need to be made (not stored) so can take a long time for levels to change
o Has 3 separate layers that each secrete a different hormone
Zona glomerulosa
o Outer layer
o Mineralcorticoid - aldosterone
Zona fasciculata
o Middle layer
o Glucocorticoid - Cortisol
Zona reticularis
o Inner layer
o Sex steroids
o Mainly androgens
• Aldosterone:
o Important in conservation of sodium
o Important in maintaining blood volume as water follows sodium
o Acts on kidney tubule cells
o Main stimulus:
Na+
K+
RAS and angiotensin II
• Adrenal sex steroids:
o From pregnonelone
o Androgens (namely DHEA and androstenedione)
o Thought to be important in foetal determination of sex and in childhood/pubertal
development of the sex organs
o Progesterone and estrogens are also secreted in very small amounts
o Disorders:
Adrenal hyperfunction of aldosterone
-excessive secretion of aldosterone
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-retention of water and Na+ -> systemic hypertension and urinary loss of K+
leading to cardiac arrhythmias
Adrenal hyperfunction of sex steroid (depends on type)
-hypersecretion of estrogens = feminisation
-hypersecretion of androgens = virilisation – facial hair
• Glucocorticoids – cortisol:
o Glucoregulatory hormone (counter regulatory hormones such as glucagon and
adrenaline) – opposes action of insulin
o All cells have receptors for cortisol
o Main role in skeletal muscle, liver and adipose tissues (metabolic effects)
o Does’t at aloe, usually ith gluago, adrenaline or GH
o Main hormone that responds to stress
o Has both pulsatile (follows ACTH and CRH) and circadian pattern of secretion
o Peak is during sleep
-decreases 1-6 hours once sleep begins then increase before awakening
o Circulates in plasma bound to CBG (cortical binding globulin)
o Binds to cytosolic receptors (inside cells)
o Binds to specific sites on DNA -> alters expression of specific genes and transcription of
specific mRNA -> proteins synthesised in response vary depending on specific genes
affected
o Increased by sympathetic activation
• Fight/flight initiated -> increase ACTH and CRH from hypothalamus -> increase cortisol in adrenal
cortex -> act on skeletal muscle to decrease protein synthesis and increase degradation ->
release aa into blood stream and decrease glucose uptake in muscles (use their own glycogen
stores) -> adipose tissue increase lipolysis to release glycerol and FA -> increase gluconeogenesis
in liver to increase blood glucose
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Endocrinology 3&4 adrenal gland and control of stress and growth and calcium regulation. Increases breathing rate: relax intestinal muscles, pupils dilate. Zona fasciculata: outer layer, mineralcorticoid - aldosterone, middle layer, glucocorticoid - cortisol. Inner layer: sex steroids, mainly androgens, aldosterone: Important in maintaining blood volume as water follows sodium: acts on kidney tubule cells, main stimulus: Retention of water and na+ -> systemic hypertension and urinary loss of k+ leading to cardiac arrhythmias. Adrenal hyperfunction of sex steroid (depends on type) Adre(cid:374)al hyperfu(cid:374)(cid:272)tio(cid:374) = cushi(cid:374)g"s sy(cid:374)dro(cid:373)e: excessive secretion of cortisol secretion, primary: failure of adrenal gland itself. Adre(cid:374)al hypofu(cid:374)(cid:272)tio(cid:374) = addiso(cid:374)"s disease: diminished secretion of cortisol, primary: failure of the adrenal gland (usually. High levels of cortisol but low levels of acth (acth independent: secondary: over secretion by the hypothalamus or pituitary gland. High levels of cortisol and high levels of. Acth or crh (acth dependent) autoimmune destruction of adrenal cortex)
