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Functions of the adrenal glands
- Protect against immediate stress
- Mediate metabolic adjustments for prolonged food/water deprivation
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Zones of the adrenal cortex
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
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Function and regulation of Zona Glomerulosa
- Secretes aldosterone (mineralocorticoid)
- Increases renal Na retention
- Increases K, H excretion
- Regulated by renin-angiotensin system
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Funtion and regulation of Zona Fasciculata
- Secrete Cortisol (glucocorticoid)
- Influence CHO metabolism
- Depress inflammatory/immune response
- Regulated by ACTH (adrenocorticotropic hormone)
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Function and regulation of Zona Reticularis
- Secretes glucocorticoids and weak androgens (DHEAS)
- Regulated by ACTH
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Function of fetal cortex
Secrete androgen precursors which are converted to androgens and estrogens in placenta, which enter maternal bloodstream
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Function of the Adrenal Medulla
- Component of sympathetic NS
- Secretes catecholamines, norepinephrine, epiniephrine
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What is the role of cortisol?
- Adaptation to prolonged food deprivation
- Inhibits inflammation, immune responses
- Increases gluconeogenesis, decreases utilization
- Increases protein breakdown, in all tissues but liver
- Increases mobilization of fatty acids
- Prevents vasodilation/hypotension
- Upholds glomerular filtration rate
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What is the role of aldosterone?
Stimulates sodium reabsorption
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How is Cortisol release regulated?
ACTH, which is in turn stimulated by CRH
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What factors increase corticotroph sensitivity to CRH?
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Mechanisms for control of ACTH
- Negative feedback by cortisol (via CRH)
- Episodic release (7-15 times per day: pulsatility important for establishing sensitivity of target)
- Diurnal rhythm (ACTH levels highest in early morning, lowest in early evening)
- Stress (secreted independent of cortisol negative feedback)
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How does cortisol travel in blood?
Bound by CBG (cortisol binding gloculin) or transcortin
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What is Cushing's syndrome and its types?
Hypercortisolism
Types: Cushing's disease, primary hypercortisolism, ectopic ACTH, CRH Excess, Iatrogenic Cushing's syndrome
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Describe Cushing's Disease and its cause
- Upward adjustment of Cortisol feedback set point
- ACTH hypersecreted, cortisol increases
- Caused by pituitary tumor that secretes ACTH (still responsive to cortisol feedback)
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Describe Primary Hypercortisolism
- Tumors arise from adrenal cortex
- Produce excess cortisol
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Describe Extopic ACTH
- Tumors of lung, GI tract produce ACTH in large amounts
- Not regulated by cortisol feedback
- CRH and pituitary ACTH are suppressed
- Duration of life very short
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Describe CRH Excess
- Excessive secretion of CRH by hypothalamus
- Related to psychiatric disorders (depression, anorexia) and alcoholism
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Describe Iatrogenic Cushing's syndrome
- Consumption of exogenous glucocorticoids
- Hypothalamic-pituitary-adrenal axis suppressed
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Types of hypocortisolism
- Primary - adrenal destruction (Addison's Disease)
- Secondary - failure of ACTH secretion from pituitary
- Tertiary - failur of CRH secretion from hypothalamus
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