A pea-sized gland in a saddle-shaped hollow of the sphenoid bone, hanging from the underside of the brain
Pituitary gland — in the sella turcica, 'Turkish saddle'.
Anatomy · Glands & the immune system
Pituitary gland
The 'master gland', about the size of a pea
Endocrine system · base of the brain
A pea-sized gland hanging by a slender stalk from the underside of the hypothalamus at the base of the brain. It sits in a bony hollow of the sphenoid bone, the sella turcica, just behind the nose and beneath the optic chiasm. Its anterior lobe makes and releases growth hormone, prolactin, ACTH, TSH, FSH and LH; its posterior lobe stores and releases oxytocin and antidiuretic hormone made in the hypothalamus. Because it controls so many other glands it is called the master gland.
How to spot them
- ▸Tiny rounded gland hanging from the floor of the brain on a stalk (the infundibulum)
- ▸Lies in the saddle-shaped sella turcica of the sphenoid bone, with a cavernous sinus on each side
- ▸Directly below the optic chiasm, so a swelling can squeeze the crossing visual fibres
- ▸Two parts: a larger glandular anterior lobe and a nervous posterior lobe
- ▸Reached by surgeons through the nose and the sphenoid sinus
What to know
The 'master gland' that directs the thyroid, adrenals and gonads
Pituitary gland — via TSH, ACTH, FSH and LH.
A tumour here can press on the optic chiasm and cut off the outer halves of both visual fields
Pituitary gland — bitemporal hemianopia.
Its posterior lobe stores oxytocin and antidiuretic hormone that are made in the hypothalamus
Pituitary gland — the neurohypophysis; the hormones travel down axons.
Too much growth hormone in adult life leads to large hands, feet and jaw
Pituitary gland — acromegaly.
Its Latin-derived name recalls the old belief that it drained phlegm into the nose
Pituitary gland — from Latin pituita, phlegm; its other name is the hypophysis.
The American neurosurgeon Harvey Cushing pioneered operating on this gland in the early 1900s
Pituitary gland — Cushing's disease is an ACTH-secreting tumour of it.
Key ideas
- The anterior lobe (adenohypophysis) is true gland tissue, regulated by releasing and inhibiting hormones sent from the hypothalamus through a private portal blood system in the stalk.
- The posterior lobe (neurohypophysis) is an extension of the brain; its hormones are made by hypothalamic neurones and travel along their axons to be released.
Quick-fire facts
- •Adult weight is roughly 0.5 g; the gland is about 1 cm across and slightly larger in pregnancy
- •Anterior lobe hormones: growth hormone, prolactin, ACTH, TSH, FSH and LH — the mnemonic 'FLAT PEG' is often used
- •Posterior lobe hormones: oxytocin and antidiuretic hormone (ADH or vasopressin)
- •The anterior lobe arises from Rathke's pouch, an upgrowth of the embryonic roof of the mouth; the posterior lobe grows down from the brain
- •The sella turcica is Latin for 'Turkish saddle', a comparison with the shape of the hollow in the sphenoid
- •The cavernous sinuses on either side carry the internal carotid artery and several cranial nerves that a large tumour can compress
- •Excess growth hormone before the growth plates close produces gigantism; after they close, acromegaly
- •Removal or destruction leads to panhypopituitarism; a severe blood-loss birth complication causing this is Sheehan's syndrome
- •Most pituitary tumours are benign adenomas and are commonly removed by transsphenoidal surgery
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