The pituitary gland is often called the master gland because it controls several other hormone glands in your body, including the thyroid and adrenals, the ovaries and testicles. ● It secretes hormones from both the front part (anterior) and the back part (posterior) of the gland. Hormones are chemicals that carry messages from one cell to another through your bloodstream.

1. Action Of Pituitary Gland :Over
Growth Harmone.
Rajat Kumar Mishra
Research Scholar
Institute Of Pharmacy
PSIT Kanpur

2. Objectives
● Structure , Synthesis and Secretion
● Regulation of Pituitary Gland
● Plasma level , binding metabolism
● Receptors and mechanism of action
● Actions of Growth Hormones.

3. Pituitary Gland
● The pituitary gland is often called the
master gland because it controls several
other hormone glands in your body,
including the thyroid and adrenals, the
ovaries and testicles.
● It secretes hormones from both the front
part (anterior) and the back part
(posterior) of the gland. Hormones are
chemicals that carry messages from one
cell to another through your bloodstream.

4. Structure Of Pituitary gland (Morphology)
● The pituitary gland, in humans, is a pea-sized gland
that sits in a protective bony enclosure called the
sella turcica.
● It is composed of three lobes: anterior, intermediate,
and posterior. In many animals, these three lobes
are distinct.
● The intermediate is avascular and almost absent in
human beings.
● The intermediate lobe is present in many animal
species, in particular in rodents, mice and rats, that
have been used extensively to study pituitary
development and function.

5. Anatomy of Pituitary Gland.
● The pituitary gland lies at the middle of
the base of the skull and is housed
within a bony structure called the sella
turcica, which is behind the nose and
immediately beneath the
hypothalamus.
● The pituitary gland is attached to the
hypothalamus by a stalk composed of
neuronal axons and the so-called
hypophyseal-portal veins.
● Its weight in normal adult humans
ranges from about 500 to 900 mg (0.02
to 0.03 ounce).

6. Secretion By Pituitary Gland
The Anterior Pituitary
● The cells of the anterior pituitary are
embryologically derived from an
outpouching of the roof of the pharynx,
known as Rathke’s pouch.
● Although the cells appear to be
relatively homogeneous under a light
microscope, there are in fact at least
five different types of cells, each of
which secretes a different hormone or
hormones.

7. Hormones released by Anterior Pituitary gland
● The thyrotrophs synthesize and secrete
thyrotropin (thyroid-stimulating hormone;
TSH).
● The gonadotrophs, both luteinizing hormone
(LH) and follicle-stimulating hormone (FSH);
the corticotrophs.
● Adrenocorticotropic hormone (ACTH)
corticotropin).
● The somatotrophs, growth hormone (GH)
somatotropin); and the lactotrophs, prolactin.

8. The Posterior Pituitary (Neurohypophysis)
● The posterior pituitary is neural in origin. Unlike the
anterior pituitary, the posterior pituitary is connected
directly to the hypothalamus via a nerve tract
(hypothalamo-hypophyseal nerve tract). It secretes two
hormones: oxytocin and antidiuretic hormone (ADH) or
vasopressin.
● The hormones are synthesized by the magnocellular
neurons located in the supraoptic and paraventricular
nuclei of the hypothalamus. The hormones are transported
in association with neurophysins proteins along the axons
of these neurons to end in nerve terminals within the
posterior pituitary.

9. Structure and function of anterior Pituitary
Hormones
The hormones of the anterior pituitary are proteins that
consist of one or two long polypeptide chains. TSH, LH, and
FSH are called glycoproteins because they contain complex
carbohydrates known as glycosides.
Each of those hormones is composed of two glycopeptide
chains, one of which, the alpha chain, is identical in all three
hormones. The other chain, the beta chain, differs in structure
for each hormone, thereby explaining the different actions of
TSH, LH, and FSH.

10. Receptor and Mechanism Of Action
● FSH and LH bind to G protein-coupled receptors to activate adenylyl cyclase enzyme, which in turn
increases intracellular cAMP. cAMP activates protein kinase A (PKA) that phosphorylates intracellular
proteins.
● These phosphorylated proteins then accomplish the final physiologic actions.
● Regulation: FSH and LH secretion are under the control of hypothalamic gonadotropin-releasing
hormone (GnRH).
● Physiological Functions: FSH and LH regulate the functions of the ovaries and the testes. In females,
FSH stimulates growth and development of follicles in preparation for ovulation and secretion of
estrogens by the mature Graafian follicle. LH triggers ovulation and stimulates the secretion of
progesterone by the corpus luteum. In males, FSH is required for spermatogenesis, and LH stimulates
testosterone secretion by Leydig cells.

11. Pituitary Gland Regulation
● It became evident that besides the five classic hormones,
the pituitary produces some of its own regulators,
including hypothalamic and peripheral hormones, as
well as an expanding list of growth factors.
● It also synthesizes cytokines- molecular mediators of
inflammatory responses. These locally produced
mediators have the capacity to alter pituitary cell
functions in an autocrine or paracrine manner, or can be
released into the circulation to act as hormones on
distant target cells.
● Accumulating evidence indicates that pituitary hormones
are also produced by target cells, including immune
cells, where they act as growth factors in an autocrine or
intracrine fashion.

12. Actions Of Growth Hormones
● GH is a single 191-amino acid chain that belongs to the
GH/PRL family, composing at least 18 distinct genes
expressed in pituitary, uterus, placenta and other tissues
● GHRH is secreted in two forms, a 44-and 40-amino acid
peptide encoded by a gene that has been sequenced and
localized in humans to chromosome 20. GHRH belongs to the
glucagon family of peptides.
● The receptors for these peptides are also related and grouped
into family B of the G protein-coupled receptor superfamily.
The coupling of GHRH with its receptor increases the
intracellular level of cAMP .
● A series of structurally diverse growth hormone-releasing
substances were synthesized during last years that are
different from the naturally occurring GHRH.
● They include GH releasing peptides (GHRPs) and mimetics
such as MK-0677. GH releasing substances proved to act via
a common receptor, GH secretagogue receptor (GHS-R) which
is distinct from the GHRH-R. GHS-R is present in the
hypothalamus and pituitary.

13. ● Peripherally, glucocorticoids reduce
circulating IGF-I level, and decrease IGF-I
and GH receptors.
● At the pituitary level, GH gene
transcription is stimulated or inhibited by
glucocorticoids, depending on the species,
duration of treatment, and experimental
conditions.
● A single injection of dexamethasone causes
an early stimulation of GH secretion
followed by a late inhibitory effect in
normal subjects . Chronic exposure to
glucocorticoids exerts a growth-suppressive
effect
● GH regulates its own secretion by acting directly on
central nervous system areas, and on hypothalamic
neurons producing GHRH and SRIF via a specific
receptor (GH-R). GH-R has a long and a short
isoform and belongs together with PRL-receptor to
the family of helix bundle peptide (HBP) cytokine
receptors. GH-R mRNA.
● And protein were demonstrated in rat somatotrophs.
However there is no proof that GH affects GH
secretion by acting directly on somatotrophs .
● Glucocorticoids act at multiple levels of the GH
pathway. They act on SRIF and GHRH producing
nuclei of the hypothalamus .

14. Vasopressin

15. Oxytocin
● Two pathways for the peripheral regulation of
oxytocin originate from areas in the nipple
and the cervix.
● In the milk-ejection reflex, stimulation of the
nipples triggers impulses which proceed
along the peripheral nerves (thoracic 3, 4, and
5) and the spinal cord to the hypothalamus,
and
● Results in the release of oxytocin from the
posterior pituitary gland.
● The released oxytocin then completes the
reflex arc by stimulating contractions in the
myoepithelial cells surrounding the alveoli
and small ducts in the breast, resulting in milk
ejection. The milk-ejection reflex can be
suppressed by the activity of higher centers in
the brain.

16. THE PITUITARY PORTAL PLASMA OXYTOCIN
● Oxytocinergic nerve fibers have been identified both in the external and
internal layers of the median eminence; however, the majority of the
fibers is found in the internal layer of the median eminence..
● The neurites in the external zone are axon terminals that originate in the
parvocellular cell bodies in the PVN. These oxytocinergic terminals are
localized in the immediate vicinity of primary capillary plexus of the
pituitary portal vascular system and appear to be a major source of the
portal OT.
● The fibers in the internal layer of the median eminence are preterminal
axons of magnocellular neurons from the PVN and SON in passage to
the posterior pituitary gland. Recently published observations suggest
that a proportion of portal OT may also be derived from these
preterminal magnocellular axons in the internal layer of the median
eminence.

17. Plasma portal level in oxytocin
● A number of experimental paradigms are available for studying
the hypothalamic regulation of PRL secretion from the
lactotropes in the anterior pituitary gland.
● The now-apparent multifactorial control of PRL
release,measurement of hypothalamic hormones in pituitary
portal blood appeared to be best suited for unraveling the
complexities of neural regulation of PRL secretion.
● The major limitation of this approach in rats is that it requires
acute anesthesia and surgical trauma..Thus, the measurement of
hypothalamic hormone secretion using the portal preparation
approach in rats appeared to provide physiologically relevant
information on the central regulatory processes.

18. By: Rajat Mishra