Pituitary Gland
A small gland at the base of the brain that controls most other hormone-producing glands.
What it means
The pituitary is a pea-sized gland at the base of the brain, often called the master gland because its hormones direct the activity of the thyroid, adrenal glands, ovaries and testes.
Among the hormones it produces are TSH, which drives the thyroid; ACTH, which drives the adrenal glands; LH and FSH, which drive the ovaries and testes; growth hormone; and prolactin.
This hierarchy explains why blood tests often measure the pituitary signal rather than the target hormone — the signal changes earlier and more sensitively.
In practice
Hormone conditions are classified by level: primary where the target gland itself has failed, and secondary where the pituitary is not signalling adequately.
Pituitary tumours are usually benign but may cause problems by pressing on adjacent structures or by overproducing a hormone.
Why it matters
Because the optic nerves cross immediately above the gland, an enlarging pituitary tumour characteristically produces loss of the outer fields of vision.
Headache with loss of peripheral vision warrants prompt investigation. A raised prolactin level is a routine part of assessing unexplained hormone abnormalities.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026