Anterior pituitary

The anterior pituitary (also called the adenohypophysis) comprises the anterior lobe of the pituitary gland and is part of the endocrine system. Under the influence of the hypothalamus, the anterior pituitary produces and secretes several peptide hormones that regulate many physiological processes including stress, growth, and reproduction.

Anatomy and development

The adenohypophysis is a pea-sized gland anterior to the neurohypophysis, caudal to the hypothalamus, and sits in the medial aspect of the brain. Its blood supply is the hypophyseal artery , and it secretes hormones into the hypophyseal vein .

The anterior pituitary is derived from the epithelial ectoderm of the roof of the embryonic mouth.

Histology

When stained by PAS , three main types of secretory cell can be seen: chromophobes (which don't take on any stain), basophils (which stain purple, and are not related to the blood cell), and acidophils (stain orange). About half of the cells are chromophobes, 40% are acidophils, and 10% are basophils.

Basophilic staining cells produce the hormones that specifically act on other endocrine organs, such as TSH, ACTH, FSH and LH. Acidophils produce growth hormone and prolactin. Chromophobes are presumed to be "empty" cells, that have already released their granules of hormone.

Electron microscopy and immunohistochemistry allow further identification of the hormone produced by the cells.

Major hormones secreted

Hormone	Target	Effect
Adrenocorticotropic hormone (ACTH)	Adrenal gland	Secretion of glucocorticoids
Follicle-stimulating hormone (FSH)	Gonads	Growth of reproductive system
Growth hormone (GH)	Liver, fat cells	Promotes growth; lipid & carbohydrate metabolism
Luteinizing hormone (LH)	Gonads	Sex hormone production
Prolactin	Ovaries, mammary glands	Secretion of estrogens/progesterone; milk production
Thyroid stimulating hormone (TSH)	Thyroid gland	Secretion of thyroid hormones