Pituitary hormones Flashcards
Where is the pituitary gland located?
In the sella turcica.
In the midline - between the two eyes.
How many parts does the hypophysis have?
2 parts.
Adenohypophysis - anteriorly.
Neurohypophyisis - posteriorly.
Connected to hypothalamus by the stalk (infundibulum).
The pituitary gland can extend in what directions?
Superiorly
Inferiorly
Laterally
The infundibulum goes through what?
The diaphragma sellae
What is the anterior border of the cavernous sinus?
Superior orbital fissure
What is the posterior border of the cavernous sinus?
Petrous part of the temporal bone.
What is the medial border of the cavernous sinus?
Body of the sphenoid bone
What is the lateral border of the cavernous sinus?
Meningeal layer of the dura mater running from the roof to the floor of the middle cranial fossa.
What is the roof of the cavernous sinus?
Meningeal layer of the dura mater that attaches to the anterior and middle clinoid processes of the sphenoid bone.
What is the floor of the cavernous sinus?
Endosteal layer of the dura mater that overlies the base of the greater wing of the sphenoid bone.
What travels through the cavernous sinus?
Abducens nerve (CN VI).
Carotid plexus (post-ganglionic sympathetic nerve fibres).
Internal carotid artery (cavernous portion).
What travels through the lateral wall of the cavernous sinus?
Oculomotor nerve (CN III)
Trochlear nerve (CN IV)
Ophthalmic (V1) and maxillary (V2) branches of the trigeminal nerve
What is unique about the cavernous sinus?
The cavernous sinus is the only site in the body where an artery (internal carotid) passes completely through a venous structure. This is thought to allow for heat exchange between the warm arterial blood and cooler venous circulation.
Mnemonic to remember contents of cavernous sinus:
OTOM CAT
Oculomotor nerve
Trochlear nerve
Ophthalmic branch
Maxillary branch
These are the lateral wall contents from superior to inferior.
Internal carotid artery
Abducens nerve
Trochlear nerve
Medial to lateral.
How does the anterior pituitary get its blood supply?
Through the portal venous circulation from the hypothalamus.
Describe the hypothalamo-pituitary-target organ axis
Hypothalamus secretes releasing hormone (TRH)
Pituitary secretes stimulating hormone (TSH)
Target organ (thyroid) secreted hormones (T3;T4)
What molecule inhibits GH?
Somatostatin
In response to GH the liver secretes what?
IGF-I
Why is prolactin production different?
It is constantly produced and inhibited by dopamine. (The dopaminergic neurone goes down the stalk and directly releases dopamine to the anterior pituitary).
List examples of diseases of the pituitary gland
Benign pituitary adenoma (functional or non)
Craniopharygioma
Trauma (structural or functional problems)
Apoplexy/Sheehans (rapid expansion due to bleeding or acute infarct.
Sheehans: major post-partum haemorrhage = hypoperfusion).
Sarcoid/TB
What are the 3 vital points of tumours?
Pressure on local structures.
Pressure on normal pituitary.
Functioning tumour.
Describe pressing on local structures more in details:
Push upwards against the optic nerve = bitemporal hemianopia.
The diaphragma sellae can be stretched = headaches.
Lateral expansion (medio-lateral temporal lobe) = seizures.
Downward = no problem, however if all the way down = abnormal connection - CSF rhinorrhoea and infection leading to meningitis.
What are the signs and symptoms of pressure on the normal pituitary gland?
Hypopituitarism
Pale
No body hair
Central obesity
Functioning tumours of the pituitary
Prolactinoma.
Acromegaly and gigantism.
Cushing’s disease.
