Anterior pituitary, also called the adenohypophysis, is the glandular, anterior lobe of the pituitary gland. The anterior pituitary regulates several physiological processes including stress, growth, and reproduction.
Its regulatory functions are achieved through the secretion of various peptide hormones that act on target organs including the adrenal gland, liver, bone, thyroid gland, and gonads. The anterior pituitary itself is regulated by the hypothalamus and by negative feedback from these target organs.
Disorders of the anterior pituitary are generally classified by the presence of over- or underproduction of pituitary hormones. For example, a prolactinoma is a pituitary adenoma that overproduces prolactin. In Sheehan's syndrome of postpartum hypopituitarism, the anterior pituitary uniformly malfunctions and underproduces all hormones. Proper function of the anterior pituitary and of the organs it regulates can often be ascertained via blood tests that measure hormone levels.
Hormone secretion from the anterior pituitary gland is regulated by hormones secreted by the hypothalamus. Neuroendocrine neurons in the hypothalamus project axons to the median eminence, at the base of the brain. At this site, these neurons can release substances into small blood vessels that travel directly to the anterior pituitary gland (the hypothalamo-hypophysial portal vessels).