Lesson 1, Topic 1
In Progress

Anatomy of the Pituitary Gland

April 11, 2024

Learning Objective: Differentiate between the hormones of the anterior lobe and those of the posterior lobe of the pituitary gland.
      The pituitary gland is also known as the hypophysis. The pituitary gland is a pea-sized gland connected to the hypothalamus by the infundibulum, a small stalk of tissue. The hormones from the pituitary control the other endocrine glands; thus, the pituitary gland is called the “master gland.” The pituitary gland is composed of two lobes. The anterior and posterior lobes act as separate glands, each having its own function.

FIGURE 24.2  Anterior and posterior pituitary hormones and the target organs. From Patton KT, Thibodeau GA: The human body in health and disease, ed 6, St. Louis, 2014, Mosby.

Anterior Lobe of the Pituitary Gland
Learning Objective: Discuss the anterior lobe of the pituitary gland and the actions of the hormones secreted.
The anterior lobe, also known as the adenohypophysis, produces and secretes these hormones (FIGURE 24.2):
            • Adrenocorticotropic hormone (ACTH): Causes the adrenal cortex to produce and release steroids (e.g., cortisol).
            • Follicle-stimulating hormone (FSH): Stimulates the development of ova (eggs) through ovulation in females and stimulates the seminiferous tubules to produce sperm in males.
            • Growth hormone (GH): Stimulates growth of the long bones and muscles in children and teens. Growth hormone is also involved with glucose metabolism in the body. Growth hormone is also called somatotropin or somatotropic hormone (STH).
            • Luteinizing hormone (LH): In females, it stimulates the ovaries to produce estrogen, ova to mature, and the production of progesterone. LH also initiates ovulation and signals the corpus luteum to develop. In men, it stimulates interstitial cells in the testes to develop and secrete testosterone. Thus, in men, LH is also called interstitial cell–stimulating hormone (ICSH).
            • Prolactin (PRL): Stimulates breast tissue development and milk production toward the end of pregnancy and after childbirth.
            • Thyroid-stimulating hormone (TSH): Stimulates the thyroid gland to release T3 and T4. (More information about the thyroid will be presented later in the chapter.)

Posterior Lobe of the Pituitary Gland
Learning Objective: Discuss the posterior lobe of the pituitary gland and the actions of the hormones secreted.
The posterior lobe, also known as the neurohypophysis, is composed of nervous tissue. It does not produce hormones but stores hormones produced by the hypothalamus. The hormones are transported from the hypothalamus to the posterior lobe directly through the infundibulum. The posterior lobe stores the hormones until it gets a signal from the hypothalamus to release them into the bloodstream. The blood then carries the hormones to the target organ (see FIGURE 24.2). Two hormones are released by the posterior lobe:
            • Antidiuretic hormone (ADH): Also called vasopressin. Stimulates contraction of the blood vessels, raising the blood pressure. It also stimulates the kidney tubules to reabsorb water, which concentrates the urine.
            • Oxytocin (OT): During the delivery of a child, OT is released and stimulates the uterine muscles to contract. This is an example of a positive feedback loop (FIGURE 24.3). OT also helps release breast milk by stimulating the contraction of the muscles surrounding the mammary ducts.

24.1 Critical Thinking Application
Cecilia is struggling to remember the hormones secreted by the posterior and anterior lobes of the pituitary gland. What might be some helpful ways to remember the hormones from this gland?