Pituitary Gland
Overview
The pituitary gland is an important structure along the base of the brain that is integral in hormonal regulation. It is composed of an anterior gland and posterior gland which are anatomically, embryologically and functionally distinct. The pituitary gland sits within the sella tursica, which is a depression along the roof of the sphenoid bone.
Embryology & Physiology
The anterior gland is derived from the upward migration of the embryologic mouth and is responsible for secreting TSH, PRL, GH, FSH/LH and MSH. The posterior gland is directly connected to the hypothalamus and results from the downward migration of the neuroectoderm from the diencephalon. The hypothalamus produces ADH and Oxytocin, which are then stored and released by the posterior gland.
Coronal MR images of the pituitary gland and adjacent structures.
It is important to recognize these relationships as patients with primary pituitary pathology may present with symptoms related to mass effect. It is not uncommon for patients with large pituitary tumors to present with bitemporal hemianopsia related to compression of the optic chiasm. The pituitary gland is outside of the blood brain barrier, which explains why it enhances normally after contrast.
Sagittal MR image of the pituitary gland and adjacent structures.
The pituitary gland is in close proximity to a number of important structures. The anterior gland is similar in signal intensity to adjacent brain tissue on T1, whereas the posterior gland is often hyperintense (bright) on T1. Some believe that this bright signal is related to the lipid within the secretory granules used to store the hormones produced by the hypothalmus (Oxytocin)
This patient presented with symptoms related to mass effect on the optic chiasm. Notice how the cystic tumor of the pitutiary gland compresses the undersurface of the chiasm.