Pituitary Gland
·
Anterior pituitary releases:
ACTH, GH, FSH, LH, TSH, PRL
·
Posterior pituitary releases:
ADH, Oxytocin
· Under dominant tonic control (stalk failure ® hormone failure): LH, FSH, GH, TSH, ACTH
·
Under dominant inhibitory control
(stalk failure ® Â): PRL
·
Vasopressin (ADH): produced in
hypothalamus, released in pituitary. Stalk failure ® polyuria
for a few weeks until Ârelease in median eminence
·
Pituitary fossa is in the
superior sphenoid bone, covered superiorly by the diaphragm sellae, with a
central aperture for the infundibulum. The suprasellar cistern includes the
infundibulum and the optic chiasm
·
Pituitary is usually 6 mm in kids,
8 mm in men and postmenopausal women, 10 mm in women of child bearing age, 12
mm in pregnancy and postpartum. Gradual involution beyond 50 years old
·
„Pituitary bright spot‟:
posterior pituitary is normally hyperdense.
Lost in diabetes insipidous
·
Normal pituitary fossa has a flat
top, or concave (dips down)
·
Microadenomas: < 10 mm, don‟t
normally take up contrast. Are usually hormone secreting (that‟s why they‟re
found)
·
Macroadenomas: > 10 mm, most
are not hormone secreting, found because of space occupying effect
·
Sellae and suprasellar lesions:
o An empty sellae is due to herniation of the suprasellar cistern in to
the sellae ® flattening of gland (with or without disturbance). Also secondary to
hypophysectomy, post-radiation or infarction
o Craniopharyngiomas: suprasellar tumours that may extend into the sellae.
Kids and young adults. Cause pituitary insufficiency, visual impairment,
hydrocephalus, hypothalamic disturbance
o Meningiomas: MRI shows close meningeal attachment and enhancement
post-contrast
o Optic nerve gliomas: in kids.
Extend along optic nerve
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