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Lecture notes Endocrinology Chronic Stress Axis - HPA Axis (BI2BB4) £7.99   Add to cart

Lecture notes

Lecture notes Endocrinology Chronic Stress Axis - HPA Axis (BI2BB4)

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The final lecture in a series for the module Endocrinology. This lecture covers the basics of the chronic stress axis, the HPA axis, related conditions and more. A great way to start your understanding of the module or to miss a lecture or two.

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  • August 7, 2022
  • 5
  • 2019/2020
  • Lecture notes
  • Dr phil knight
  • All classes
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robbieseal
29.11.19


L8 – Chronic stress axis (Hypothalamic-pituitary-adrenocortical axis)
Keywords:
Stress (a process initiated by evens that threaten, harm or
challenge an organism)

Lecture:
 Anterior pituitary (mostly all proteins)
o Adrenocorticotropin = peptide
 HPA axis
o Secretion of CRH or AVP in hypothalamus
o Stimulates adrenocorticotrophic hormone
(ACTH)
 ACTH = peptide hormone in family of
melanocortin all from POMC
precursor
 Zona fasciculata (cortisol secretion via ACTH)
o Cholesterol – rate limiting via ACTH moving
from cytoplasm to mitochondria→
pregnenolone
o 5 minutes between stimulation and
cholesterol
o Thickened zona with increased stress
 Constant circadian rhythm (max between 6-8am and fall)
 Reversed rhythm in nocturnal
 Cortisol (steroid)
o Hydrophobic (80% use binding protein – transcortin (liver))
o Stimulates glucose synthesis (gluconeogenesis – make from FA/proteins)
 Stimulates lipolysis to increase FA production
 Stimulates muscle breakdown (get AAs for glycogenesis)
o Stored as glycogen
o Stimulates appetite
o Anti-inflammatory (immunosuppression to ↓ neutrophils)
 Using glucocorticoids for immunosuppressants/arteritis
 Down reg for ACTH axis (- feedback)
 Disfunction of the HPA axis (Cushing’s)
o SYNDROME = Cortisol over-production (side-effect of steroid medication)
 Use of glucocorticoids
o DISEASE = Natural cause = tumor in pit (synth ACTH/CRH (less common))
 Ectopic = tumor producing ACTH in ling
 Adrenal tumor = direct cortisol synth
o Symptoms
 Central obesity
 Thinning of the skin
 Bruising (burst caps)
 Hypertension
 Bone and muscle wasting

, 29.11.19


o Diagnosis
 Cortisol presence in the urine
 Rarely measure ACTH in blood bc unstable
 If adrenal tumor = low levels of ACTH
 Ectopic tumor = high levels of ACTH ]
 Pituitary tumor = middle
 Dexamethasone (glucocorticoid)
 Normal person = suppress ACTH
 Pit tumor = not suppressing
 Petrosal sinus fluid
 Take blood samples (high levels of ACTH)
o Treatment
 Steroids (reduce glucocorticoid given – slow reduction as adrenals would not
synth cortisol independently)
 Pit tumor = remove surgically
 Transnasal approach (via nose)
 Adrenalectomy
 Remove adrenals (easier)
 Low cortisol levels so large ACTH levels
o Nelson’s syndrome = can get pigmentation change

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