About the size and shape of a pea, located in the sella turcica of the sphenoid bone, attached to the hypothalamus via a stalk called the infundibulum. It has two major lobes, one neural and one glandular. Posterior Lobe (Neurohypophysis) – composed of nervous tissue; releases neurohormones that it receives ready-made from the hypothalamus; oxytocin and anti-diuretic hormone (ADH); released on demand in response to nerve impulses from hypothalamic neurons. Anterior Lobe (Adenohypophysis) – composed of glandular tissue; manufactures and releases its own hormones as a result of stimulation by releasing hormones from the hypothalamus; called the master endocrine gland; releases 6 hormone products which all function via second messenger systems. Four of the six are hormones that regulate the functioning of other endocrine glands: thyroid stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle stimulating hormone (FSH), and luteinizing hormone (LH) Remaining two affect non-endocrine targets: growth hormone(GH) and prolactin. Anterior Pituitary Hormones 1. Thyroid Stimulating Hormone (TSH) – Stimulates the thyroid gland to secrete thyroid hormone. 2. Adrenocorticotropic Hormone (ACTH) – Stimulates the adrenal cortex to release corticosteroid hormones (glucocorticoids, gonadocorticoids, and mineralocorticoids). 3,4. Gonadotropins – Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH)
Regulate the function of the gonads (ovaries and testes). In both sexes, FSH stimulates gamete production, while LH promotes the production of gonadal hormones (estrogen and testerone. 5. Growth Hormone (GH) – Stimulates most body cells to increase in size and divide. Its major targets are the bones and skeletal muscles. Induces protein synthesis and encourages the use of fats for fuel, thus conserving glucose. GH release is controlled by hormones from the hypothalamus which stimulates or inhibits its release.