Pharmacology – III
PHL-418
Endocrine Pharmacology
Lecture 1:
By:
Endocrine system Introduction
Hypothalamic and Pituitary Hormones
Majid Ahmad Ganaie
M. Pharm., Ph.D.
Assistant Professor
Department of Pharmacology
E mail: majidsays@gmail.com
Content Layout with List
• ENDOCRINE SYSTEM INTRODUCTION
• CLASSES OF HORMONES
• SOURCES OF HORMONES
• HYPOTHALAMIC AND ANTERIOR PITUITARY HORMONES
• HORMONES OF THE POSTERIOR PITUITARY
The Endocrine System
• The endocrine system controls many body functions
• Exerts control by releasing special chemical substances into the blood called
hormones
• Hormones affect other endocrine glands or body systems
The neuroendocrine system, which is controlled by the pituitary and hypothalamus, coordinates
body functions by transmitting messages between individual cells and tissues. This contrasts with
the nervous system, which communicates locally through electrical impulses and neurotransmitters
directed through neurons to other neurons or to specific target organs, such as muscle or glands.
•
HORMONE: A substance that is released in one tissue and travels through the
circulation (usually) to the target tissue.
•
Hormones reach all parts of the body, but only target cells are equipped to respond
•
Hormones are secreted in small amounts and often in bursts (pulsatile secretion)
Endocrine System
Functions:
• Maintain Internal Homeostasis
• Support Cell Growth
• Coordinate Development
• Coordinate Reproduction ,
fertility, sexual function
• Facilitate Responses to
External Stimuli
4 Classes of Hormones
• Peptide/ Protein (Range from 3 amino acids to hundreds of amino acids in size. )
• Steroid
• Amine (Thyroid hormones
and Catecholamines)
• Eicosanoid (Fatty acid derivatives )
Location of receptors
• On cell surface: Peptides and proteins
• In cytoplasm: Steroids
• In nucleus: Thyroid hormones
The hormones fall into two general classes
based on their solubility in water.
The water soluble { amine and
peptide/protein hormones} are secreted by
exocytosis, travel freely in the bloodstream,
and bind to cell-surface receptors.
The lipid soluble hormones { thyroid
hormone, steroid hormones and Vitamin
D3}. diffuse across cell membranes, travel
in the bloodstream bound to transport
proteins, and diffuse through the
membrane of target cells .
Fat-soluble
hormone
Watersoluble
hormone
Signal receptor
TARGET
CELL
(a)
Transport
protein
Signal
receptor
NUCLEUS
(b)
Mechanisms of endocrine disease
• Hormone deficiency treated with Hormone replacement therapy (HRT)
• Hormone excess treated with Specific antagonists or release inhibitors.
• Hormone resistance treated with Sensitizers
Sources of hormones:
- Natural:
Human (GH; LH & FSH; hCG);
Animal (Insulin, T3 & T4)
- Biosynthetic:
Insulin (Porcine & Bovine)
- Synthetic:
Most hormones and their antagonists
DNA recombinant technology
HYPOTHALAMIC AND ANTERIOR PITUITARY HORMONES
The hormones secreted by the hypothalamus and the pituitary are all peptides
or low molecular weight proteins that act by binding to specific receptor sites on
their target tissues. The hormones of the anterior pituitary are regulated by
neuropeptides that are called either “releasing” or “inhibiting” factors or
hormones. These are produced in the hypothalamus, and they reach the
pituitary by the hypophyseal portal system.
Each hypothalamic regulatory hormone controls the release of a specific
hormone from the anterior pituitary.
Hormones of the anterior and posterior pituitary are administered
intramuscularly (IM), subcutaneously, or intranasally because their peptidyl
nature makes them susceptible to destruction by the proteolytic enzymes of the
digestive tract.
A. Adrenocorticotropic hormone (corticotropin)
Mechanism of action:
ACTH binds to receptors on the surface of the
adrenal cortex, thereby activating G protein–
coupled processes that ultimately stimulate the
rate-limiting step in the adrenocorticosteroid
synthetic pathway (cholesterol to pregnenolone)
Therapeutic uses:
As a diagnostic tool for differentiating between
primary adrenal insufficiency (Addison disease,
associated with adrenal atrophy) and secondary
adrenal insufficiency (caused by the inadequate
secretion of ACTH by the pituitary).
Adverse effects: Short-term use of ACTH is
usually well tolerated. With longer use, toxicities
are similar to those of glucocorticoids and
include hypertension, peripheral edema,
hypokalemia, emotional disturbances, and
increased risk of infection.
B. Growth hormone (somatotropin)
GH is released in a pulsatile manner, with the highest levels occurring
during sleep. Somatotropin influences a wide variety of biochemical
processes (for example, cell proliferation and bone growth are
promoted)
Mechanism of action: Although many physiologic effects of GH are
exerted directly at its targets, others are mediated through the
somatomedins—insulin-like growth factors 1 and 2 (IGF-1 and IGF-2).
Therapeutic uses:
Somatropin is used in the treatment of GH deficiency or growth failure
in children. Somatropin is administered by subcutaneous or IM
injection. Although the half-life of GH is short (approximately 25
minutes), it induces the release of IGF-1 from the liver, which is
responsible for subsequent GH-like actions.
Adverse effects: Adverse effects of somatropin include pain at the
injection site, edema, arthralgias, myalgias, flu-like symptoms, and an
increased risk of diabetes.
C. Somatostatin (Growth hormone-inhibiting hormone)
In the pituitary, somatostatin binds to receptors that suppress GH and thyroid-stimulating hormone release.
Somatostatin not only inhibits the release of GH but also that of insulin, glucagon, and gastrin.
Octreotide and lanreotide are synthetic analogs of somatostatin. Their half-lives are longer than that of the natural
compound, and depot formulations are available, allowing for administration once every 4 weeks.
They have found use in the treatment of acromegaly and in diarrhea and flushing associated with carcinoid
tumors.
Adverse effects of octreotide include diarrhea, abdominal pain, flatulence, nausea, and steatorrhea. Gallbladder
emptying is delayed, and asymptomatic cholesterol gallstones can occur with long-term treatment.
D. Gonadotropin-releasing hormone
Pulsatile secretion of gonadotropin-releasing hormone (GnRH) from the
hypothalamus is essential for the release of the gonadotropins follicle
stimulating hormone (FSH) and luteinizing hormone (LH) from the
anterior pituitary. However, continuous administration of GnRH inhibits
gonadotropin release through down-regulation of the GnRH receptors on
the pituitary.
Continuous administration of synthetic GnRH analogs, such as
leuprolide, goserelin, nafarelin, and histrelin, is effective in suppressing
production of the gonadotropins
Suppression of gonadotropins, in turn, leads to reduced production of
gonadal steroid hormones (androgens and estrogens).
Thus, these agents are effective in the treatment of prostate cancer,
endometriosis, and precocious puberty.
They are contraindicated in pregnancy and breast-feeding.
E. Gonadotropins
The gonadotropins (FSH and LH) are glycoproteins that are produced
in the anterior pituitary.
The regulation of gonadal steroid hormones depends on these agents. They find use in
the treatment of infertility.
Menotropins (also known as human menopausal gonadotropins or hMG) are obtained
from the urine of postmenopausal women and contain both FSH and LH.
Urofollitropin is FSH obtained from postmenopausal women and is devoid of LH.
Follitropin alfa and follitropin beta are human FSH products manufactured using
recombinant DNA technology.
Human chorionic gonadotropin (hCG) is a placental hormone that is excreted in the
urine of pregnant women.
The effects of hCG and choriogonadotropin alfa (made using recombinant DNA technology) are essentially identical
to those of LH.
All of these hormones are injected via the IM or subcutaneous route.
F. Prolactin
Prolactin is a peptide hormone that is also secreted by the anterior pituitary.
Its primary function is to stimulate and maintain lactation.
Its secretion is inhibited by dopamine acting at D2 receptors.
Drugs that act as dopamine antagonists (for example, metoclopramide and antipsychotics such as risperidone) can
increase the secretion of prolactin.
Hyperprolactinemia, which is associated with galactorrhea and hypogonadism, is treated with D2 receptor
agonists, such as bromocriptine and cabergoline. Both of these agents also find use in the treatment of pituitary
microadenomas.
HORMONES OF THE
POSTERIOR PITUITARY
 In contrast to the hormones of the
anterior lobe of the pituitary, those of
the posterior lobe, vasopressin and
oxytocin, are not regulated by
releasing hormones. Instead, they are
synthesized in the hypothalamus,
transported to the posterior pituitary,
and released in response to specific
physiologic signals, such as high
plasma osmolarity or parturition.
 Both hormones are administered intravenously and have
very short half-lives.
A. Oxytocin
Oxytocin is used in obstetrics to stimulate uterine contraction and induce labor. Oxytocin also causes milk ejection
by contracting the myoepithelial cells around the mammary alveoli.
B. Vasopressin
Vasopressin (antidiuretic hormone) is structurally related to oxytocin. Vasopressin has both antidiuretic and
vasopressor effects.
In the kidney, it binds to the V2 receptor to increase water permeability and reabsorption in the collecting tubules.
Thus, the major use of vasopressin is to treat diabetes insipidus.
Other effects of vasopressin are mediated by the V1 receptor, which is found in liver, vascular smooth muscle
(where it causes constriction), and other tissues.
Desmopressin, an analog of vasopressin, has minimal activity at the V1 receptor, making it largely free of pressor
effects. This analog is longer acting than vasopressin and is preferred for the treatment of diabetes insipidus and
nocturnal enuresis. For these indications, desmopressin may be administered intranasally or orally.
Thank You
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