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2011-06-08 08:36:45
ACTH Glucocorticoids

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  1. Functions of the adrenal glands
    • Protect against immediate stress
    • Mediate metabolic adjustments for prolonged food/water deprivation
  2. Zones of the adrenal cortex
    • Zona glomerulosa
    • Zona fasciculata
    • Zona reticularis
  3. Function and regulation of Zona Glomerulosa
    • Secretes aldosterone (mineralocorticoid)
    • Increases renal Na retention
    • Increases K, H excretion
    • Regulated by renin-angiotensin system
  4. Funtion and regulation of Zona Fasciculata
    • Secrete Cortisol (glucocorticoid)
    • Influence CHO metabolism
    • Depress inflammatory/immune response
    • Regulated by ACTH (adrenocorticotropic hormone)
  5. Function and regulation of Zona Reticularis
    • Secretes glucocorticoids and weak androgens (DHEAS)
    • Regulated by ACTH
  6. Function of fetal cortex
    Secrete androgen precursors which are converted to androgens and estrogens in placenta, which enter maternal bloodstream
  7. Function of the Adrenal Medulla
    • Component of sympathetic NS
    • Secretes catecholamines, norepinephrine, epiniephrine
  8. 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
  9. What is the role of aldosterone?
    Stimulates sodium reabsorption
  10. How is Cortisol release regulated?
    ACTH, which is in turn stimulated by CRH
  11. What factors increase corticotroph sensitivity to CRH?
    • Epinephrine
    • ADH
  12. 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)
  13. How does cortisol travel in blood?
    Bound by CBG (cortisol binding gloculin) or transcortin
  14. What is Cushing's syndrome and its types?

    Types: Cushing's disease, primary hypercortisolism, ectopic ACTH, CRH Excess, Iatrogenic Cushing's syndrome
  15. 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)
  16. Describe Primary Hypercortisolism
    • Tumors arise from adrenal cortex
    • Produce excess cortisol
  17. 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
  18. Describe CRH Excess
    • Excessive secretion of CRH by hypothalamus
    • Related to psychiatric disorders (depression, anorexia) and alcoholism
  19. Describe Iatrogenic Cushing's syndrome
    • Consumption of exogenous glucocorticoids
    • Hypothalamic-pituitary-adrenal axis suppressed
  20. Types of hypocortisolism
    • Primary - adrenal destruction (Addison's Disease)
    • Secondary - failure of ACTH secretion from pituitary
    • Tertiary - failur of CRH secretion from hypothalamus