Cortisol Flashcards
The mammalian stress axis is?
hypothalamic-pituitary-adrenocortical Axis
the hypothalamus has?
has neuroendocrine function on the ant. pituitary
how does blood drain away from ant pit via?
efferent veins and into the peripheral circulatiom
what hormones does the anterior pituitary secrete?
gonadotrophin thyrotrophin GH Prolocatin adrenocorticoptrophin
What hormones does the posterior pituitary secrete?
Oxytocin and vasopressin
What does stress related stimuli cause the hypothalamus to secrete?
Corticotrophin releasing hormone (CRH) and Arginine vasopressin (AVP) by hypothalamus
How many amino acids is CRH?
41aa
how many aa is AVP?
9aa
What does AVP and CRH do?
stimulates the secretion of adrenocorticotrophic hormone (ACTH) by the ant. pit gland
How many amino acids is ACTH?
39aa
What is co-secreted with ACTH?
other peptides from the pro-opiomelanocortin (POMC) (ACTH derived from POMC)
What is the circadian rhythm of the HPA axis?
circadian rhythm exist in the circulation g level of cortisol
How does cortisol circulate?
complexed with corticosteroid binding globulin : TRANSCORTIN
why does cortisol circulate as transcortin?
to protect it from metabolism and inactivation in liver
what are the major effects of cortisol?
energy for gluconeogenesis, obtained from the breakdown of fats and the release of fatty acids
increases the metabolism of muscle proteins for gluconeogenesis and inhibits protein synthesis
What is cushings syndrome?
The over production of cortisol
What is the cause of cushings syndrome?
normally caused by a benign tumour at the pituitary
a result of excess CRH production which derives ACTH secretion in turn stimulates excess release of cortisol
Excess ACTH production from an ACTH producing tumour
Adrenal tumour
What is cushings syndrome often an extreme side effect of?
steroid medication
What are the symptoms of cushings syndrome?
central obesity thinning of skin bruising hypertension muscle and bone wasting
How would you diagnose cortisol overproduction?
- measure cortisol/ACTH levels in urine/plasma
- Normal/very low ACTH concentration – ACTH independent e.g. adrenal tumour or the use of steroid medication
- High ACTH concentration - probably due to an ectopic ACTH-producing tumour.
- Moderately high ACTH levels - tends to be due to a pituitary tumour
- Dexamethasone suppression test
Describe the dexamethasone suppression test
low dose will suppress ACTH levels in normal pts, but not in cushings disease.Sample blood from inferior petrosal sinus. Blood from pituitary drains into here and can sample with a catheter – shows source of ACTH
Treatment of Cushings syndrome
Reduce steroid medication
surgical removal of the tumour
adrendlectomy - leads to high levels of POMC peptides due to lack of -ve feedback - leads to hyper pigmentation called NELSONS SYNDROME
What is underproduction of cortisol known as?
Addisons disease
