Which gland is often called the 'master gland' of the endocrine system?

The gland often called the “master gland” of the endocrine system is the pituitary gland.

The pituitary is a small, kidney-bean-sized endocrine gland at the base of the brain, housed in a bony depression called the sella turcica. It releases hormones that influence growth, reproduction, lactation, stress responses, thyroid activity, and adrenal function. Its broad influence over other endocrine glands explains the nickname.

The label is useful but simplified. The hypothalamus sits above the pituitary and directs much of its activity through releasing hormones and neural signals, so the two structures work as a hypothalamic–pituitary control system. The pituitary does not independently command every endocrine process.

The gland has anterior and posterior lobes with different origins and roles. The anterior pituitary produces hormones such as growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, luteinizing hormone, and prolactin. The posterior lobe stores and releases oxytocin and antidiuretic hormone, which are produced by neurons in the hypothalamus. This distinction is why the pituitary’s anatomy is more complex than its nickname suggests.