The Pituitary Gland and Hypothalamus

By the end of this section, you will be able to: • Explain the interrelationships of the anatomy and functions of the hypothalamus and the posterior and anterior lobes of the pituitary gland • Identify the two hormones released from the posterior pituitary, their target cells, and their principal actions • Identify the six hormones produced by the anterior lobe of the pituitary gland, their target cells, their principal actions, and their regulation by the hypothalamus The hypothalamus pituitary complex can be thought of as the command center of the endocrine system. This complex secretes several hormones that directly produce responses in target tissues, as well as hormones that regulate the synthesis and secretion of hormones of other glands. In addition, the hypothalamus pituitary complex coordinates the messages of the endocrine and nervous systems. In many cases, a stimulus received by the nervous system must pass through the hypothalamus pituitary complex to be translated into hormones that can initiate a response. The hypothalamus is a structure of the diencephalon of the brain located anterior and inferior to the thalamus (Figure 1 (Hypothalamus Pituitary Complex )). It has both neural and endocrine functions, producing and secreting many hormones. In addition, the hypothalamus is anatomically and functionally related to the pituitary gland (or hypophysis), a bean-sized organ suspended from it by a stem called the infundibulum (or pituitary stalk). The pituitary gland is cradled within the sellaturcica of the sphenoid bone of the skull. It consists of two lobes that arise from distinct parts of embryonic tissue: the posterior pituitary (neurohypophysis) is neural tissue, whereas the anterior pituitary (also known as the adenohypophysis) is glandular tissue that develops from the primitive digestive tract. The hormones secreted by the posterior and anterior pituitary, and the intermediate zone between the lobes are summarized in Table 1. ∗Version 1.3: Jun 19, 2013 10:13 am -0500 †http://creativecommons.org/licenses/by/3.0/ http://cnx.org/content/m46699/1.3/ OpenStax-CNX module: m46699 2 Hypothalamus Pituitary Complex Figure 1: The hypothalamus region lies inferior and anterior to the thalamus. It connects to the pituitary gland by the stalk-like infundibulum. The pituitary gland consists of an anterior and posterior lobe, with each lobe secreting di erent hormones in response to signals from the hypothalamus. Pituitary Hormones Pituitary lobe Associated hormones Chemical class E ect Anterior Growth hormone (GH) Protein Promotes growth of body tissues Anterior Prolactin (PRL) Peptide Promotes milk production from mammary glands continued on next page http://cnx.org/content/m46699/1.3/ OpenStax-CNX module: m46699 3 Anterior Thyroid-stimulating hormone (TSH) Glycoprotein Stimulates thyroid hormone release from thyroid Anterior Adrenocorticotropic hormone (ACTH) Peptide Stimulates hormone release by adrenal cortex Anterior Follicle-stimulating hormone (FSH) Glycoprotein Stimulates gamete production in gonads Anterior Luteinizing hormone (LH) Glycoprotein Stimulates androgen production by gonads Posterior Antidiuretic hormone (ADH) Peptide Stimulates water reabsorption by kidneys Posterior Oxytocin Peptide Stimulates uterine contractions during childbirth Intermediate zone Melanocyte-stimulating hormone Peptide Stimulates melanin formation in melanocytes