Pituitary Disease Flashcards
What is the 4 axis of endocrine system
Hypothalamus-pituitary-adrenal
GH
Hypothalamus-pituitary-thyroid
Hypothalamus-pituitary-gonadal
Why is negative feedback important
Maintain equilibrium
What is primary hyperfunction
Increased target hormone at target cells & inhibit at pituitary & hypothalamus
What is primary hypofunction
Stimulate at pituitary & hypothalamus due to low concentration
What 5 factors affects secretion
Negative feedback
Pulsatile secretion
Effects of stress (increases GH, cortisol & prolactin)
Effects of intense exercise (suppress gonadal axis)
Effects development (GH = length & age)
How to assess for hypofunction
Stimulation test
How to assess for hyperfunction
Suppression test
How does the hypothalamus-pituitary-adrenal axis flow
Corticotropin releasing hormone stimulate pituitary to release adenocorticotropic hormone that stimulate adrenal glands to secrete cortisol
Affects all tissue by inflammation & increase blood glucose
How does the GH axis flow
GH releasing hormone acts on pituitary to secrete GH acting on muscles, liver & bone for growth
How does the hypothalamus-pituitary-thyroid axis flow
Thyrotropin releasing hormone acts on pituitary to secrete thyroid stimulating hormone to stimulate thyroid to produce thyroid hormone to increase cells metabolism & prolactin
What inhibits prolactin
Dopamine
What 2 things stimulates prolactin
Stress & TRH
How does the hypothalamus-pituitary-gonadal axis flow
Gonadotropin releasing hormone acts on pituitary to secrete LH & FSH & act on gonads to produce gametes & sex hormones
What sequence does hypopituitarism deficiency occur
GH, FSH & LH
ACTH
TSH
What is hypopituitarism
Decreased production of one or more pituitary hormone resulting from hypothalamic or pituitary disease
What is panhypopituitarism
All hormones are deficient
What is spared with hypopituitarism
Posterior pituitary
What is the clinical findings in hypopituitarism in adults & children
Children: growth failure
Adults: reproductive dysfunction
What is 4 causes of hypopituitarism
Congenital: hypoplasia of pituitary or chromosome 22 detection syndrome
Acquired: tumour, surgery, radiation, trauma
When is growth hormone secreted the most
Pulsatile hormone so increased secretion at night & decrease w/ age
What is the 2 major actions of GH
- Metabolic: antagonist insulin action causing hyperglycemia & promote lipolysis in fasting state
- Stimulate production of insulin like growth factor: anabolic action by inhibiting protein breakdown & stimulate muscle & bone growth
What 6 factors stimulate GH
Hypoglycemia
Amino acids
Fasting
Exercise
Sleep
Adrenergic stimulant clonidine
What 2 factors inhibit GH
Somatostatin
Hyperglycemia
What is the clinical presentation of GH deficiency in children, neonates & adults
Children: short stature
Neonate: hypoglycemia
Adults: decreased muscle mass & increase adipose
What test should be performed to diagnose growth hormone deficiency
Decreased IGF-1
Failure of GH increase w/ stimulation test (fasting, exercise, clonidine, insulin induce hypoglycemia)
What is 5 causes of GH deficiency
Congenital
Tumour
Trauma
Idiopathic
Receptor defects
What is clinical features of GH excess in children & adults
Children: gigantism
Adults: acromegaly
What is the cause for excess GH
GH or GHRH producing tumour
How to diagnose GH excess
Failure to suppress GH w/ oral glucose load
What is the function of prolactin
Initiates & sustains lactation during pregnancy
What is a cause of low prolactin
Pituitary damage like Sheehan syndrome
What is 5 causes of high prolactin
Prolactin producing tumor
Stalk effect
Dopamine antagonist
Stress
Primary hypothyroidism
What is 2 clinical features of elevated prolactin
Galactorrhoea
Amenorrhea
What is another name for ADH
Vasopressin
Where is ADH produced
In hypothalamus & stored in posterior pituitary
What is the function of ADH
Secreted when there is an increase in osmolality to decrease in blood volume to reabsorb water
What is ADH main target
Kidneys to change water permeability at collecting ducts
What is ADH deficiency called
Diabetes insipidus
What is 4 clinical features of diabetes insipidus
Polydipsia
Polyuria
Dehydration
Severe hypernatraemia
What is the osmolality to the urine & serum in diabetes insipidus
Urine has decreased osmolarity & serum has increased osmolality due to water excretion
What is the two types of diabetes insipidus
Central due to deficiency in ADH
Nephrogenic due to nephrogenic resistance to ADH
What is 4 causes of central diabetes insipidus
Genetic, trauma, inflammation or vascular condition
What is 3 causes of nephrogenic diabetes insipidus
Genetic, drugs & renal pathologies
How is diabetes insipidus diagnosed
Water deprivation test w/ serial urine collections & ADH is administered once osmolality of urine plateaus
What is the results & diagnosis of water deprivation test
Normal: 700-800
DI: plateau at 200-300
Central: increased osmolality after injection of ADH
Nephrogenic: no change after ADH injection
What is SIADH
Syndrome of inappropriate ADH
Failure of low plasma osmolality to suppress ADH release
Fluid retention stimulates RAAS maintaining normal water balance but Na is lost
What is osmolality of the urine & serum in SIADH
Hyponatraemia & low osmolality serum
High urine osmolality
What is 4 causes of SIADH
Tumor
Trauma
Drugs
Infection
Where is human chorionic gonadotropin secreted from
Placenta
When is HCG secreted
At pregnancy
At very high levels with pregnancy related tumour
How does HCG & TSH cross react
Same a-subunits
What happens when TSH & HCG cross react
Increased HCG cross react w/ TSH receptor in thyroid leading to increased secretion of thyroxine/T4 & inhibits TSH production (- feedback)
HCG peaks at 12 weeks & once HCG decrease TSH will increase
How does HCG & LH cross react
Same a-subunit
What is HCG & LH cross reaction used for
To test for testosterone deficiency
If HCG is administered & testosterone should normally increase
How is the different subunits differentiated in the labs
In lab looks for a & b subunits
