pituitary disease Flashcards
where is the pituitary gland located
dangles down from the hypothalamus and sits in the sella turcica of the sphenoid bone
what hormones are stored in the posterior pituitary
ADH and oxytocin
what does ADH do
acts to increase water reabsorption by increasing expression of aquaporin channels in the kidney in response to increase serum osmolarity (as a result of decreased water body)
what does oxytocin do
aids in the stimulation of uterine contraction and ejection of breast milk during breast feeding
which hypothalamic hormone is involved in the thyroid axis
TRH
which hypothalamic hormone is involved in the steroid axis
CRH
which hypothalamic hormone is involved in the growth axis
GHRH
which hypothalamic hormone is involved in the prolactin axis
dopamine
which hypothalamic hormone is involved in the sex axis
GRH
which pituitary hormone is involved in the thyroid axis
TSH
which pituitary hormone is involved in the steroid axis
ACTH
which pituitary hormone is involved in the growth axis
growth hormone
which pituitary hormone is involved in the prolactin axis
prolactin
which pituitary hormones are involved in the sex axis
FSH and LH
what is the target hormone for the thyroid axis
T3/T4
what is the target hormone for the steroid axis
cortisol
what is the target hormone for the growth axis
IGF1
what are the target hormones for the sex axis
testosterone, oestrogen and progesterone
what makes prolactin unique (2)
- it is the only one with no target hormone
- dopamine provides negative control over prolactin release, whereas all of the other hypothalamic hormones stimulate the anterior pituitary
hypopituitarism causes
can be isolated to a specific hormone or involve a complete lack of pituitary hormones (pan-hypopituitarism)
hypothalamus causes
- tumour
- infection (TB, meningitis, syphilis)
- genetic (Kallman syndrome, which is isolated deficit of gonadotrophs, associated with absent smell and colour blindness)
pituitary stalk causes
- surgery
- trauma
- carotid artery aneurysm
- tumour (meningioma, craniopharyngioma)
pituitary causes
- irradiation
- non-functioning adenoma
- infiltration (haemochromatosis, amyloid, sarcoid)
- ischaemia
what is Sheehan syndrome
pan hypopituitarism due to pituitary ischaemia and necrosis following a post-partum haemorrhage
Sheehan syndrome presentation
ischaemia due to bleeding of pituitary tumours
hypopituitarism presentation
- lack of CRH (adrenal insufficiency)
- absent TSH (hypothyroidism)
- absent GHRH (central obesity, atherosclerosis, weakness, loss of balance)
- lack of GRH in females (amenorrhoea, reduced fertility/libido, breast atrophy)
- lack of GRH in males (erectile dysfunction, reduced libido, reduced muscle bulk, hypogonadism)
- low blood pressure, can’t lactate if pregnancy, no response to stress
hypopituitarism diagnosis
- static tests: TSH, T3/T4, FSH, LH, testosterone, IGF-1, prolactin
- short synacthen: adrenal axis and ACTH
- insulin tolerance test: adrenal and GH axis (should rise in the presence of hypoglycaemia induced by giving insulin)