Basics of endocrine Flashcards
What are the different types of hormone receptors?
GPCR
RTK
Nuclear
What is the structure of GPCR?
7 transmembrane domain
What are the major intracellular signalling molecues?
cAMP
IP3
What are the effectors of GCRP receptors?
Adenylyl cyclase
Phospholipase C
GIRk
PI3 kinase
What hormones are released by the anterior pituitary?
GH LH/FSH ACTH TSH PRL
What hormones are released from the posterior pituitary?
ADH
Oxytocin
What needs to be taken into consideration when measuring hormones?
Pattern of secretion Presence of carrier proteins Intefering agents Stability of hormone (consisder half life) Absolute concentrations
What hormones commonly require evaluation?
Thyroid Steroid - cortisol GH evaluation Reproductive and sex hormones Prolactin Calcium and PTH Renin/ aldosterone Catecholamines Gut hormones
Raised TSH suggests what?
Hypothyroid
Supressed TSH sugests what?
Hyperthyroid
When might TSH not be a reliable marker of thyroid status?
In secondary thyroid disease where the issue arises from the pituitary and therefore the levels of TSH will be off
How is pituitary function assessed?
9am cortiol TSH, fT4/3 Prolactin IGF1 (GH) LH, FSH, E2 (females)/ testosterone (males) U&E, plasma/urine osmolality
What rhythm does cortisol secretion follow?
Circadian rhythm
Diurinal
When are cortisol levels at their highest and lowest?
Highest at 9am
Lowest at midnight
What axis will 9am cortisol give an indication of?
HPA axis - ACTH release
How is growth hormone measured?
IGF-1 to indicate GH hypersecretion
Formal GH axis requires dynamic testing
What pattern will female sex hormones show?
Menstrual cycle
When should testosterone be measured?
9am
What is prolactin secreted by?
Lactotroph cells of the anterior pituitary
What inhibits the production of prolactin?
Dopamine
What mediates the effects of prolactin?
Prolactin receptor (PRLR)
What will act on the hypothalamus in the regulation of thirst and water?
Hyperosmolarity
Angiotensin 2
Sympathetic stimualtion
Decreased atrial firing
What is the action of vasopressin 1?
Constriction of blood vessels
Increased systemic vascualr resistance
Increased arterial pressure
What is the action of vasopressin 2?
Acts on the kidneys to increased fluid reabsorption increasing the blood volume
This increases arterial pressure
What is the common precursor of all steroid hormones?
Pregenolone
What dynamic test is used for hormone excess?
Suppression test
What dynamic test is used for hormone deficiency?
Stimulation test
What condition is characterised by primary cortisol deficiency?
Addisons disease
What is cushings syndrome?
Cortisol excess
What can cause cushings syndrome?
Pituitary origin
Adrenal origin
Ectopic ACTH
Exogenous steroids
What is synacthen tests?
A stimulation test - used for addisons
When is the dexamethasone suppression test used?
In cushings syndrome
What are the signs and symptoms of cushings syndrome?
Cushoingoid faces Acne Hirsutism Abdominal striae Obesity Interscapular and suprascapular fat pads Proximal myopathy Osteoporosis Hypertension Impaired glucose tolerance
What is cushings disease?
Tumour arising from the corticotroph cells of the anterior pititary
Where does cushings DISEASE originate?
Pituitary
Where does ACTH independent cushings originate?
Adrenal adenoma/carcinoma
What happens to the adrenal gland in ACTH-independent cushings?
Bilateral macronodular adrenal hyperplasia
What causes ectopic ACTH?
Malignancy - commonly lung cancer
What causes exogenous cushings?
Oral, inhaled, topical, injectable steroid use
What will hapen to the ACTH levels in ACTH-independent cushings?
Levels should be undetectable
What are the screening tests for cushings?
1mg overnight dexamethasone suppression test
24 hour urinary free cortisol
Midnight cortisol
What is the formal diagnostic test for cushings??
Low dose dexamethasone supression test - failure to suppress = cushings
What type of cushings will a low ACTH show?
Adrenal origin
What type of cushings will a raised ACTH show?
Need to disinguish between cushings disease (pituitary origin) and ectopic ACTH
What is the formal diagnostic test for cushings disease?
Rise in cortisol and ACTH on CRH (corticortophic releasing hormone) test indicates a pituitary source
What is an inferior petosal sinus sampling?
Used to lateralize the tumour prior to surgery
