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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 ( [link] ). 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 [link] .

Hypothalamus–pituitary complex

This illustration shows the hypothalamus-pituitary complex, which is located at the base of the brain and shown here from a lateral view. The hypothalamus lies inferior and anterior to the thalamus, which is sits atop the brainstem. The hypothalamus connects to the pituitary gland by the stalk-like infundibulum. The pituitary gland looks like a sac containing two balls hanging from the infundibulum. The “balls” are the anterior and posterior lobes of the pituitary. Each lobe secretes different hormones in response to signals from the hypothalamus.
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 different hormones in response to signals from the hypothalamus.
Pituitary Hormones
Pituitary lobe Associated hormones Chemical class Effect
Anterior Growth hormone (GH) Protein Promotes growth of body tissues
Anterior Prolactin (PRL) Peptide Promotes milk production from mammary glands
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

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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