Which gland is known as the master gland?

The pituitary, a pea-sized structure hanging under the brain, which secretes hormones that control other glands - thyroid, adrenals, ovaries and testes - as well as growth hormone and the hormones of childbirth and lactation.

Master is a promotion it does not quite deserve. The pituitary is itself directed by the hypothalamus immediately above it, which monitors the body and issues releasing hormones down a private blood supply - so the master gland has a manager. The arrangement is the junction between the nervous system and the endocrine system, which is why stress, sleep and light exposure end up altering hormones.

Its size and position make it clinically awkward. A tumour there is usually benign and still serious, because it presses on the optic nerves crossing just above and takes out peripheral vision, and because it disrupts whichever hormone the affected cells produced - too much growth hormone in adulthood produces acromegaly, in childhood gigantism. It is also reached surgically through the nose and the sphenoid sinus, which is a considerably better route than through the skull.