Endocrine Disorders Flashcards
define endocrine signalling
a signalling molecule is secreted into the blood stream, acting on distant cells throughout the body
give the 3 types of signalling
autocrine - signalling acts on the same molecules
paracrine - signal is released into interstitial fluid and acts on nearby cells
endocrine - signal released into bloodstream, acts on distant cells
describe the endocrine system and its purpose
endocrine glands - secrete hormones which travel via blood to target cells
- regulates all biological processes in the body
describe the Hypothalamus-Pituitary Axis and how it controls the endocrine system.
- hypothalamus
- receive signal
- produce ‘releasing hormones’
- hormones act on pituitary gland
- pituitary produces ‘trophic hormones’
- bloodstream
- act on endocrine gland
- produces end productive or acts directly on the cells
where is the pituitary found? how heavy is it?
found at the base of the brain
-0.5-1grams
what are the two parts of the pituitary?
anterior pituitary
aka adenohypophysis
posterior pituitary
aka neurohypophysis
describe how the adenohypohysis and neurohypophysis works.
adenohyphosis
- releasing hormones arrive via bloodstream - portal circulation
- it then releases 6 different trophic hormones into systemic bloodstream
neurohypohysis
- signal arrives via neurons
- releases 2 trophic hormones
- ADH and oxytocin
describe the path of Thyrotropin-Releasing Hormone (TSH)
- releasing hormone from the hypothalamus
- anterior pituitary
- stimulates release of thyroid-stimulating hormone from pituitary
- acts on the thyroid gland
- produces T3 and T4
describe the 2 ways in which the endocrine system is regulated.
- by specific circumstance - e.g. diet and insulin
- negative feedback
- signal is sent to hypothalamus or pituitary to reduce the amount of hormone release/trophic hormone production
what is hyperpituitarism and how does it occur?
the excess production of trophic hormones
- due to hyperplasias, adenomas, carcinomas, hypothalamus disorders, secretion of pituitary-like hormones from non-pituitary tumours
what is hypopituitarism and how does it occur?
when there is a deficient production of trophic hormones
- due to damage of the tissue
- ischaemia, radiation, surgery, inflam disorders, postpartum ischaemic necrosis and mass effect of non-functional pituitary tumour
what is Sheehan Syndrome, how does it link to the pituitary?
post-partum ischaemic necrosis
- women became hypovolemic
- excess blood loss
- hypopituitarism
how can the dysfunction of the pituitary affect the eye, inter-cranial pressure and emergency from a tumour?
eye
- pituitary sits on top of optic nerve
- mass can push on the optic chiasm
= visual defects
- mass can raise the intercranial pressure
- sudden haemorrhage into a tumour
= sudden enlargement
= pituitary apoplexy
what is the most common cause of hyperpituitarism?
pituitary adenomas
- excess production of trophic hormones
what is the most common pituitary tumour?
pituitary anterior lobe tumour
pituitary adenomas - epidemiology
epidemiology
- 35-60 years
how are pituitary adenomas classified?
by the cell type and hormones produced
if it produces functional hormones
- detected early
- deregulates chemicals in the body
- symptoms appear fast
if non-functional hormones are produced
- detected later on
- why?
- no chemical imbalances
- symptoms only appear when the size of tumour is great enough
give 3 types of pituitary adenomas
lactotroph pituitary adenoma
somatotroph pituitary adenoma
corticotroph pituitary adenoma
what is the most common pituitary adenoma?
lactotroph pituitary adenoma
describe lactotroph pituitary adenomas
- what are they also known as
- what hormone is produced
- what are the clinical features
- diagnostic effectivity
AKA prolactinomas
hormone = prolactin
clinical features
- amenorrhea - loss of menstrual cycle
- galactorrhoae - excess production of milk
- loss of libido
- infertility
- easier to diagnose women v men
describe somatotroph pituitary adenomas
- what hormones are produced
- clinical features
hormone = excess growth hormones
clinical features
- children = gigantism
- adults = acromegaly
- oversized limbs
describe cortiocotroph pituitary adenomas
- the hormones
- path of the hormone
hormone
- adrenocorticotrophic hormone
ACTH
- hormone travels to adrenal gland
- stimulates excess secretion of cortisol
corticotroph pituitary adenomas lead to hypersecretion of cortisol, what major syndrome does this lead to?
Cushing’s syndrome
describe the structure of the thyroid
- bi-lobed organ
- isthmus joins the left and right side
- anterior to larynx
- level 5-7 of vertebrae