IN THIS ISSUE Review: •Human Pituitary Hormones Tips and Techniques: •A Guide to Hormone Reference Preparations

As the primary regulator of the endocrine system, the pituitary gland is the most important of the endocrine glands. The major glands of the endocrine system include the pituitary, thyroid, and parathyroid glands, and the pancreas, adrenal cortex, ovaries, and testes. The pituitary regulates the actions of most of these glands and many other body functions. It, in turn, is regulated by the hypothalamus through nervous stimulation and through the production of various hormone-releasing factors. In humans the pituitary is located at the base of the brain, attached to the hypothalamus (see figure 1). It weighs approximately 700 mg and consists of posterior, intermediate, and anterior lobes, each with its own unique function. The posterior lobe controls the release of two polypeptide hormones: vasopressin and oxytocin. These are synthesized in the hypothalamus and transported to the posterior lobe, where they are stored in secretory granules until release. Vasopressin (antidiuretic hormone) increases the reabsorption of water into the blood by the kidneys, thereby decreasing urine production. It also causes vasoconstriction of peripheral blood vessels, slowing the heart rate and increasing blood pressure. Oxytocin stimulates uterus contraction during labor and the milk release response during lactation. The intermediate lobe releases melanocyte-stimulating hormone (melanotropin), which controls the darkening of the skin. In the anterior lobe, releasing hormones from the hypothalamus stimulate the release of several hormones: prolactin (PRL) and human growth hormone (GH, somatotropin) from the acidophilic cells; follicle-stimulating hormone (FSH, follitropin), luteinizing hormone (LH, lutropin), and thyroid-stimulating hormone (TSH, thyrotropin) from the basophilic cells; and adrenocorticotropic hormone (ACTH, corticotropin) from the chromophobic cells. It is these anterior pituitary hormones that are the focus of this review. Non-glycosylated Hormones of the Anterior Pituitary