The pituitary gland is small — about the size of a pea — and it hangs off the bottom of the hypothalamus on a thin stalk called the infundibulum. It sits in a bony pocket of the skull base called the sella turcica, which means Turkish saddle in Latin. The shape really does resemble a small saddle, and the pituitary nestles within it like a rider.
The pituitary has two anatomically and functionally distinct lobes. The anterior pituitary (adenohypophysis) is true glandular tissue. It produces and releases six major hormones — ACTH, TSH, FSH, LH, GH, and prolactin — under the control of hypothalamic releasing factors that arrive through the hypothalamic-pituitary portal vein system. The posterior pituitary (neurohypophysis) is not really a separate gland; it is an extension of hypothalamic axon terminals that release oxytocin and vasopressin directly into the bloodstream.
The anatomic neighborhood matters clinically. Just above the sella turcica sits the optic chiasm — the crossing point of the optic nerves. When a pituitary tumor expands upward (as macroadenomas commonly do), it compresses the chiasm from below. The first fibers to be compressed are the crossing fibers from the nasal halves of both retinas, which carry information from the temporal visual fields. The result is the classic visual field defect of pituitary tumor: bitemporal hemianopsia — loss of the outer half of vision in each eye.
Patients often do not notice this loss until it has progressed significantly, because they unconsciously turn their heads to compensate. A formal visual field assessment (Goldmann or automated perimetry) is therefore part of the workup whenever a pituitary lesion is suspected, and bitemporal field cuts on routine eye examination should prompt MRI of the pituitary region.
Pituitary adenomas come in two clinically important categories. Functional adenomas secrete excess hormone — most commonly prolactinomas (galactorrhea, amenorrhea, infertility, headache), or growth-hormone-secreting tumors (acromegaly in adults, gigantism in children). Non-functional adenomas produce no hormones but cause symptoms through mass effect — headache, visual field loss, and panhypopituitarism as normal pituitary tissue is compressed.
Hold the geography. A pea-sized gland in a bony saddle, beneath a crossing of optic nerves. Small location, enormous consequences when something grows here.