Pituitary Gland: Anterior LobeBy: Galindo, Fesas, Crandall, Aquiles, Houston 7A

❖ anterior pituitary gland is part of the 3 sections of the pituitary gland that is a pea sized structure located at the base of the brain, just below the hypothalamus.

Where is the anterior pituitary gland located?

Hormones produced● Adrenocorticotropic hormone (ACTH): ACTH stimulates the adrenal

glands to produce hormones.● Follicle-stimulating hormone (FSH): FSH works with LH to ensure

normal functioning of the ovaries and testes.● Growth hormone (GH): GH is essential in early years to maintaining a

healthy body composition and for growth in children. In adults, it aids healthy bone and muscle mass and affects fat distribution.

● Luteinizing hormone (LH): LH works with FSH to ensure normal functioning of the ovaries and testes.

● Prolactin: Prolactin stimulates breast milk production.● Thyroid-stimulating hormone (TSH): TSH stimulates the thyroid gland to

produce hormones.

Hormone effect on the body

The anterior lobe contains six types of secretory cells, all but Gonadotropins, secrete only one of the anterior lobe hormones. All of them secrete their hormone in response to hormones reaching them from the hypothalamus of the brain.

Thyroid Stimulating Hormone (TSH)

Stimulates the thyroid gland to secrete its hormone thyroxine (T4). ❖ Some people develop antibodies

against their own TSH receptors. When these bind the receptors, they "fool" the cell into making more T4 causing hyperthyroidism. The condition is called thyrotoxicosis or Graves' disease. Thyroid can enlarge to twice its size or more. Increased heartbeat, muscle weakness, disturbed sleep, ect.

Follicle Stimulating Hormone (FSH)

Synthesis and release of FSH is triggered by the arrival from the hypothalamus of gonadotropin-releasing hormone (GnRH). The effect of FSH depends on one's sex. ❖ FSH in Females: releases estrogen❖ FSH in Males: stimulates the production of sperm

Luteinizing Hormone (LH)❖ LH in females: a surge of LG

trigger the completion of meiosis I of the egg and its release in the middle of the menstrual cycle.

❖ LH in Males: acts on the interstitial cells (Leydig cells) of the testes stimulating them to synthesize and secrete the male sex hormone, testoterone.

Prolactin (PRL)

During pregnancy it helps in the preparation of the breast for future milk production.Prolactin secretion is:❖ stimulated by Thyrotropin-releasing hormone (TRH)❖ repressed by estrogens and dopamine

Growth Hormone (GH)❖ also called somatropin❖ the GH-secreting cells are

stimulated to synthesize and release GH by the intermittent arrival of growth hormone releasing hormone (GHRH) from the hypothalamus.

The Adrenocorticotropic Hormone (ACTH)

❖ acts on the cells of the adrenal cortex, stimulating the to produce:➢ glucocorticoids, like cortisol➢ mineralocorticoids, like

aldosterone➢ androgens (like testerone)

❖ In the fetus, ACTH stimulates the adrenal cortex to synthesize a precursor of estrogen called dehydroepiandrosterone sulfate which helps prepare the mother for giving birth.

❖ Hypersecretion of ACTH is a frequent cause of Cushing's syndrome.

Maintenance of Homeostasis❖ The homeostatic maintenance of the anterior pituitary is crucial to our

physiological well being. ❖ Increased plasma levels of TSH induce hypothermia through a mechanism

involving decreased metabolism and cutaneous vasodilation.❖ Increased levels of LH also result in hypothermia but through a decreased

metabolism action.ACTH and prolactin increase metabolism and induce cutaneous vasoconstriction, increased plasma levels also result in hypothermia; follicle-stimulating hormone (FSH) also may cause hypothermia if increased beyond homeostatic levels through an increased metabolic mechanism only.

❖ When there is an increase in hormones secreted by the pituitary it can lead to formations of tumors. (Hyperpituitarism) ➢ Three types of tumors cause:

■ Acromegaly- excessive secretion of growth hormone. This can cause gigantism.

■ Prolactinoma- hypersecretion prolactin■ ACTH excess- excess cortisol which causes

Cushing’s disease. ❖ A decrease of hormones released by the anterior pituitary is

called hypopituitarism. ➢ Hypo-secretion can cause:

■ Dwarfism ■ Addison’s Disease (lack of cortisol)

Improper Function of Pituitary Gland: Anterior Lobe

Fixing the Pituitary Gland: Anterior Lobe

❖Removal of tumors may help with diseases:➢ Surgical removal➢ Radiation Therapy➢ Medication Therapy

❖ Injections of missing hormones can also be used to treat the Anterior Lobe

Feedback Mechanisms and Antagonistic Hormones

Feedback Mechanism: A process in which the level of one substance influences the level of another substance (positive feedback: same direction, initiate or accelerate; negative feedback: opposite direction, inhibit or slow down).

�The pituitary gland produces hormones that are part of both positive (LH, GH

and Prolactin) and negative (ACTH, TSH and FSH) mechanisims, however, negative feedback mechanisms control the release of most hormones. The hypothalamus detects changes in the body and sends a message to the pituitary to release the hormone that adjusts the changes.

Antagonistic Hormones: Hormones that have the opposite effect in the body and act to return the body conditions to within acceptable limits from opposite extremes.

Releasing and Release-Inhibiting Hormones and Glands

The anterior lobe releases hormones upon receiving releasing or inhibiting hormones from the hypothalamus. These hypothalamic hormones tell the anterior lobe whether to release more of a specific hormone or stop production of the hormone.

Releasing hormones are produced in the hypothalamus to stimulate production of anterior pituitary hormones.

Releasing hormones, such as thyrotropin-releasing hormone (TRH) and gonadotropic-releasing hormone (GnRH), stimulate the anterior pituitary to release TSH, FSH and LH.

Release-inhibiting hormones (RIH): Hormones that inhibit the secretion of another hormone.

Inhibiting hormones: (GHIH) Growth hormone-inhibiting hormone (prevents the secretion of hormones hGH and TSH), prolactin-inhibiting hormone, somatostatin, and (MSH) melanocyte stimulating hormone-inhibiting hormone

The anterior lobe of the pituitary gland releases hormones and sends signals to other glands to secrete hormones.

Bibliography http://en.wikipedia.org/wiki/Anterior_pituitaryhttp://www.aans.org/Patient%20Information/Conditions%20and%20Treatments/The%20Pituitary%20Gland%20and%20Pituitary%20Tumors.aspxhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Pituitary.htmlhttp://apbrwww5.apsu.edu/thompsonj/Anatomy%20&%20Physiology/2010/2010%20Exam%20Reviews/Exam%205%20Final%20Review/CH%2016%20General%20Endocrine%20Terminology.htmhttp://www.biology-online.org/dictionary/Feedback_mechanismhttp://www.answers.com/Q/What_are_the_antagonistic_hormonehttp://www.innerbody.com/image/endo01.htmlhttp://www.encyclopedia.com/doc/1O6-releaseinhibitinghormone.htmlhttp://homepage.smc.edu/wissmann_paul/intranetstuff/dept/scienceLRC/wissmann_site/pituitary.htmhttp://www.endocrineweb.com/endocrinology/overview-pituitary-glandhttp://www.cliffsnotes.com/sciences/anatomy-and-physiology/the-endocrine-system/antagonistic-hormones