PITUITARY DISEASE Flashcards
What covers the pituitary gland?
The fibrous diaphragma sellae
What lies directly above the pituitary gland?
The optic chiasm
What lies lateral to the pituitary gland?
The cavernous sinus containing cranial nerves 3, 4 and 6
What is the blood supply to the pituitary gland?
Superior hypophyseal arteries which are branches of the internal carotid supplies the anterior gland, whilst the posterior gland is supplied by the inferior hypophyseal arteries.
What are the hormones produced by the anterior pituitary gland?
Growth hormone Thyroid stimulating hormone Adrenocorticotrophic hormone Luteinizing hormone Follicular stimulating hormone Prolactin Melanocyte stimulating hormone
What are the hormones produced by the posterior pituitary gland?
The posterior pituitary gland does not produce hormones. It secretes hormones made in the hypothalamus.
What are the hormones secreted by the posterior pituitary gland?
Oxytocin
ADH
How is the control of the release of prolactin different from the hormonal feedback of the other hormones released from the anterior pituitary gland?
Hypothalamic regulation of the release is inhibitory (via dopamine) rather than a stimulating hormone
If a tumour prevents the hypothalamic hormones from reaching the anterior pituitary gland, what will happen to the levels of pituitary hormones?
They will all decrease except for prolactin which will increase as its regulation by the hypothalamus is inhibitory.
What are the two receptors of AHD and where are they found?
V1A - vascular smooth muscle and ADH causes vasoconstriction
V2 - distal convoluted tubule and collecting duct of the kidney. Causes water reabsorption
How do patients with pituitary tumours present?
Headache
Visual disturbance - often bilateral temporal hemianopia
Inappropriate hormone secretion - presenting as a endocrine picture
Hyposecretion due to compression - also presenting as a endocrine picture
Amenorrhea or loss of libido
What is the difference between a microadenoma of the pituitary gland and a macro adenoma?
Microadenomas are less than 10 mm in diameter and tend not to affect adjacent structures such as the optic chiasm. (These are most common)
Macro adenomas are more than 10 mm in diameter and often the patient presents with other signs consistent with adjacent structures being affected.
What is the most common type of anterior pituitary adenoma?
Prolactinoma
Are prolactinomas more common in men or women?
Women
What are the presenting features of prolactinoma in a female patient?
Oligomenorrhea / Amenorrhea - this is why women present earlier
Galactorrhoea
Infertility
How might a male patient with a prolactinoma present?
Lethargy Reduced libido Erectile dysfunction Impotence Hypogonadism Visual field defects Headache Galactorrhoea
Why do female patients with a prolactinoma become infertile?
Prolactin interferes with the release of GnRH which inhibits LH and FSH
Other than prolactinoma, what are the other possible causes of inappropriate hyperprolactinaemia and galatorrhoea?
Dopamine antagonists used for Parkinson’s treatment.
Renal failure (kidneys excrete prolactin)
Non-functioning tumours which produce hyperprolactinaemia by dopaminergic inhibition of prolactin release
How would you examine a patient with suspected prolactinoma?
Visual field assessment - bitemporal hemianopia
Assess for diplopia - cavernous sinus involvement
Check for signs of hyperprolactinaemia (galatorrhoea, hypogonadism in males…)
What blood tests would you order for someone with a suspected prolactinoma?
Blood tests: serum levels of prolactin TSH and thyroxine insulin like growth factor FHS, LH and oestrogen/testosterone ACTH and cortisol
What imaging would you order for someone with a suspected prolactinoma?
MRI or CT head
Radiolabelled dopamine receptor antagonist can also aid visualisation
Other than blood tests and imaging, what other investigations might you order in someone with a suspected prolactinoma?
Suppression tests - adenomas will tend to have reduced negative feedback
Measure:
GH in response to oral glucose tolerance test, which should suppress GH
ACTH in response to dexamethasone, which should suppress CRH and ACTH
What are the four ways of treating excess hormone production?
Bromocriptine - dopamine agonist
Where does the pituitary gland sit?
In the sella turcica, a hollow in the sphenoid bone.
