Pituitary Gland:
Anterior Lobe
By: Galindo, Fesas, Crandall,
Aquiles, Houston 7A
Where is the anterior pituitary
gland located?
❖ 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.
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; folliclestimulating hormone (FSH) also may cause hypothermia if increased beyond
homeostatic levels through an increased metabolic mechanism only.
Improper Function of Pituitary Gland: Anterior
Lobe
❖ 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)
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
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