Thyroid hormones T3 and T4 are produced by the thyroid gland and regulate metabolism. T4 is converted to the more active T3 in tissues. Their production requires iodine and is regulated by TSH from the pituitary which is inhibited by thyroid hormone feedback. Thyroid hormones act through nuclear receptors to increase gene transcription and metabolism. Deficiency causes hypothyroidism while excess causes hyperthyroidism, and both can impact growth, development and multiple body systems.
Thyroid hormone,
structure of hormone,
synthesis of thyroid hormone,
mechanism of Thyroid hormone action,
Physiological effect of Hormone,
Disorders related with thyroid hormone,
drugs used in treatment for the thyroid disorders.
Second ppt on endocrine system, describing hypothalamus, pituitary and thyroid glands.
This describes the hormones from these glands and their mode of action etc
As a component of the endocrine system, both male and female gonads produce sex hormones. Male and female sex hormones are steroid hormones and as such, can pass through the cell membrane of their target cells to influence gene expression within cells. Gonadal hormone production is regulated by hormones secreted by the anterior pituitary in the brain. Hormones that stimulate the gonads to produce sex hormones are known as gonadotropins. The pituitary secretes the gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These protein hormones influence reproductive organs in various ways. LH stimulates the testes to secrete the sex hormone testosterone and the ovaries to secrete progesterone and estrogens. FSH aids in the maturation of ovarian follicles (sacs containing ova) in females and sperm production in males.
PHYSIOLOGY
OF
THYROID
HORMONES
Understand the significance of the conversion of tetraiodothyronine (T4) to triiodothyronine (T3) and reverse T3 (rT3) in extrathyroidal tissues.
Understand how thyroid hormones produce their cellular effects.
Describe the physiological effects of thyroid hormones in the body.
Outline the mechanisms for regulation of thyroid hormone.
Correlate knowledge to hypo- and hypersecretion of thyroid hormones
Thyroid hormone,
structure of hormone,
synthesis of thyroid hormone,
mechanism of Thyroid hormone action,
Physiological effect of Hormone,
Disorders related with thyroid hormone,
drugs used in treatment for the thyroid disorders.
Second ppt on endocrine system, describing hypothalamus, pituitary and thyroid glands.
This describes the hormones from these glands and their mode of action etc
As a component of the endocrine system, both male and female gonads produce sex hormones. Male and female sex hormones are steroid hormones and as such, can pass through the cell membrane of their target cells to influence gene expression within cells. Gonadal hormone production is regulated by hormones secreted by the anterior pituitary in the brain. Hormones that stimulate the gonads to produce sex hormones are known as gonadotropins. The pituitary secretes the gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These protein hormones influence reproductive organs in various ways. LH stimulates the testes to secrete the sex hormone testosterone and the ovaries to secrete progesterone and estrogens. FSH aids in the maturation of ovarian follicles (sacs containing ova) in females and sperm production in males.
PHYSIOLOGY
OF
THYROID
HORMONES
Understand the significance of the conversion of tetraiodothyronine (T4) to triiodothyronine (T3) and reverse T3 (rT3) in extrathyroidal tissues.
Understand how thyroid hormones produce their cellular effects.
Describe the physiological effects of thyroid hormones in the body.
Outline the mechanisms for regulation of thyroid hormone.
Correlate knowledge to hypo- and hypersecretion of thyroid hormones
A power point presentation on thyroid hormones and thyroid inhibitors on subject of pharmacology suitable for reading by undergraduate medical students.
an overall overview in corticosteroids and its application in oral and maxillofacial diagnostic medicine and pathology drawing to the conclusions of the limitations and drawbacks of these medicines. i have also included the precautions to be taken in dental therapeutic procedures fo
Presentation for Medical undergraduates for teaching pharmacology. It deals with Physiology of steroid hormones and their action along with agents which are used therapeutically with their action, adverse effects and therapeutic uses.
Thyroid function tests help to determine if your thyroid is not working correctly. If blood levels of thyroid hormone are high, the brain senses this and sends a message to stop producing TSH.
Thyroid hormone (The Guyton and Hall physiology)Maryam Fida
THYROID HORMONE
Location:
The thyroid gland located below the larynx on each side of and anterior to the trachea.
Largest Endocrine Hormone
Secretion:
secretes:
1. thyroxine (T4)
2. triiodothyronine (T3)
3. Also secretes calcitonin (an important hormone for calcium metabolism)
Cell: Thyrotopes
secretion is controlled by thyroid-stimulating hormone (TSH) from the anterior pituitary gland.
93% T4 & 7% T3
T4→T3 in tissues
Qualitatively same
Differ in Rapidity & Intensity of action.
T3 is 4 times more potent than T4, but decrease conc. In blood & decrease half life.
T3 and T4 combine mainly with thyroxine-binding globulin.
More than 90% of Thyroid hormone that binds with cellular receptors is T3.
T4
No effect for 2-3 days after injection
Long Latent Period.
Activity peaks in 10-12 days & ↓↓ with a half life of 15 days.
In some cases it takes 6 weeks-2 months.
T3
4 times rapid
Latent Period 6-12 hours
Peak in 2-3 days
Composed of large numbers of closed follicles filled with colloid and lined with cuboidal epithelial cells that secrete into the interior of the follicles
The major component of colloid is the large glycoprotein Thyroglobulin contains the thyroid hormones within its molecule.
50mg/year, 1mg/week
Ingested iodine in the form of iodides
Iodides ingested orally are absorbed from GIT
⅕ removed from the blood by thyroid cells for synthesis of hormones; rest excreted through kidneys.
Basal membrane of thyroid cells has an active pump to push iodides to interior (Iodine Pump).
Normally 30% more conc. Inside
Max. active 250% more conc. Inside
The rate of Iodine trapping is influenced by conc. of TSH
TSH stimulates and hypophysectomy greatly diminishes the activity of the iodide pump in thyroid cells.
Introduction:
@ Thyroid releases T3 & T4
@ The ratio of T4 to T3 is 5:1, so most of the hormone released is
thyroxine
@ Most of the T3 in the blood is derived from thyroxine
@ T3 is three to four times more potent than T4
@ The affinity of the receptor site for T3 is about ten times higher than that for T4
Thyroid Gland and Disease of Thyroid GlandRanadhi Das
The thyroid gland is one of the largest endocrine glands.
The thyroid gland is located immediately below the larynx and anterior to the upper part of the trachea. It weighs about 15-20g.
It consists of 2 lateral lobes connected by a narrow band of thyroid tissue called the isthmus.
The isthmus usually overlies the region from the 2nd to 4th tracheal cartilage.
This is a content made by the students of Pharmacy dept of Comilla University about the Endocrine system, In this you can easily find the glands in out body and their functions. and specific organs which secrete specific hormones for our body. figures are added to make it more convenient. thank you all.
R3 Stem Cells and Kidney Repair A New Horizon in Nephrology.pptxR3 Stem Cell
R3 Stem Cells and Kidney Repair: A New Horizon in Nephrology" explores groundbreaking advancements in the use of R3 stem cells for kidney disease treatment. This insightful piece delves into the potential of these cells to regenerate damaged kidney tissue, offering new hope for patients and reshaping the future of nephrology.
Leading the Way in Nephrology: Dr. David Greene's Work with Stem Cells for Ki...Dr. David Greene Arizona
As we watch Dr. Greene's continued efforts and research in Arizona, it's clear that stem cell therapy holds a promising key to unlocking new doors in the treatment of kidney disease. With each study and trial, we step closer to a world where kidney disease is no longer a life sentence but a treatable condition, thanks to pioneers like Dr. David Greene.
Global launch of the Healthy Ageing and Prevention Index 2nd wave – alongside...ILC- UK
The Healthy Ageing and Prevention Index is an online tool created by ILC that ranks countries on six metrics including, life span, health span, work span, income, environmental performance, and happiness. The Index helps us understand how well countries have adapted to longevity and inform decision makers on what must be done to maximise the economic benefits that comes with living well for longer.
Alongside the 77th World Health Assembly in Geneva on 28 May 2024, we launched the second version of our Index, allowing us to track progress and give new insights into what needs to be done to keep populations healthier for longer.
The speakers included:
Professor Orazio Schillaci, Minister of Health, Italy
Dr Hans Groth, Chairman of the Board, World Demographic & Ageing Forum
Professor Ilona Kickbusch, Founder and Chair, Global Health Centre, Geneva Graduate Institute and co-chair, World Health Summit Council
Dr Natasha Azzopardi Muscat, Director, Country Health Policies and Systems Division, World Health Organisation EURO
Dr Marta Lomazzi, Executive Manager, World Federation of Public Health Associations
Dr Shyam Bishen, Head, Centre for Health and Healthcare and Member of the Executive Committee, World Economic Forum
Dr Karin Tegmark Wisell, Director General, Public Health Agency of Sweden
Antibiotic Stewardship by Anushri Srivastava.pptxAnushriSrivastav
Stewardship is the act of taking good care of something.
Antimicrobial stewardship is a coordinated program that promotes the appropriate use of antimicrobials (including antibiotics), improves patient outcomes, reduces microbial resistance, and decreases the spread of infections caused by multidrug-resistant organisms.
WHO launched the Global Antimicrobial Resistance and Use Surveillance System (GLASS) in 2015 to fill knowledge gaps and inform strategies at all levels.
ACCORDING TO apic.org,
Antimicrobial stewardship is a coordinated program that promotes the appropriate use of antimicrobials (including antibiotics), improves patient outcomes, reduces microbial resistance, and decreases the spread of infections caused by multidrug-resistant organisms.
ACCORDING TO pewtrusts.org,
Antibiotic stewardship refers to efforts in doctors’ offices, hospitals, long term care facilities, and other health care settings to ensure that antibiotics are used only when necessary and appropriate
According to WHO,
Antimicrobial stewardship is a systematic approach to educate and support health care professionals to follow evidence-based guidelines for prescribing and administering antimicrobials
In 1996, John McGowan and Dale Gerding first applied the term antimicrobial stewardship, where they suggested a causal association between antimicrobial agent use and resistance. They also focused on the urgency of large-scale controlled trials of antimicrobial-use regulation employing sophisticated epidemiologic methods, molecular typing, and precise resistance mechanism analysis.
Antimicrobial Stewardship(AMS) refers to the optimal selection, dosing, and duration of antimicrobial treatment resulting in the best clinical outcome with minimal side effects to the patients and minimal impact on subsequent resistance.
According to the 2019 report, in the US, more than 2.8 million antibiotic-resistant infections occur each year, and more than 35000 people die. In addition to this, it also mentioned that 223,900 cases of Clostridoides difficile occurred in 2017, of which 12800 people died. The report did not include viruses or parasites
VISION
Being proactive
Supporting optimal animal and human health
Exploring ways to reduce overall use of antimicrobials
Using the drugs that prevent and treat disease by killing microscopic organisms in a responsible way
GOAL
to prevent the generation and spread of antimicrobial resistance (AMR). Doing so will preserve the effectiveness of these drugs in animals and humans for years to come.
being to preserve human and animal health and the effectiveness of antimicrobial medications.
to implement a multidisciplinary approach in assembling a stewardship team to include an infectious disease physician, a clinical pharmacist with infectious diseases training, infection preventionist, and a close collaboration with the staff in the clinical microbiology laboratory
to prevent antimicrobial overuse, misuse and abuse.
to minimize the developme
Struggling with intense fears that disrupt your life? At Renew Life Hypnosis, we offer specialized hypnosis to overcome fear. Phobias are exaggerated fears, often stemming from past traumas or learned behaviors. Hypnotherapy addresses these deep-seated fears by accessing the subconscious mind, helping you change your reactions to phobic triggers. Our expert therapists guide you into a state of deep relaxation, allowing you to transform your responses and reduce anxiety. Experience increased confidence and freedom from phobias with our personalized approach. Ready to live a fear-free life? Visit us at Renew Life Hypnosis..
How many patients does case series should have In comparison to case reports.pdfpubrica101
Pubrica’s team of researchers and writers create scientific and medical research articles, which may be important resources for authors and practitioners. Pubrica medical writers assist you in creating and revising the introduction by alerting the reader to gaps in the chosen study subject. Our professionals understand the order in which the hypothesis topic is followed by the broad subject, the issue, and the backdrop.
https://pubrica.com/academy/case-study-or-series/how-many-patients-does-case-series-should-have-in-comparison-to-case-reports/
CRISPR-Cas9, a revolutionary gene-editing tool, holds immense potential to reshape medicine, agriculture, and our understanding of life. But like any powerful tool, it comes with ethical considerations.
Unveiling CRISPR: This naturally occurring bacterial defense system (crRNA & Cas9 protein) fights viruses. Scientists repurposed it for precise gene editing (correction, deletion, insertion) by targeting specific DNA sequences.
The Promise: CRISPR offers exciting possibilities:
Gene Therapy: Correcting genetic diseases like cystic fibrosis.
Agriculture: Engineering crops resistant to pests and harsh environments.
Research: Studying gene function to unlock new knowledge.
The Peril: Ethical concerns demand attention:
Off-target Effects: Unintended DNA edits can have unforeseen consequences.
Eugenics: Misusing CRISPR for designer babies raises social and ethical questions.
Equity: High costs could limit access to this potentially life-saving technology.
The Path Forward: Responsible development is crucial:
International Collaboration: Clear guidelines are needed for research and human trials.
Public Education: Open discussions ensure informed decisions about CRISPR.
Prioritize Safety and Ethics: Safety and ethical principles must be paramount.
CRISPR offers a powerful tool for a better future, but responsible development and addressing ethical concerns are essential. By prioritizing safety, fostering open dialogue, and ensuring equitable access, we can harness CRISPR's power for the benefit of all. (2998 characters)
QA Paediatric dentistry department, Hospital Melaka 2020Azreen Aj
QA study - To improve the 6th monthly recall rate post-comprehensive dental treatment under general anaesthesia in paediatric dentistry department, Hospital Melaka
CHAPTER 1 SEMESTER V - ROLE OF PEADIATRIC NURSE.pdfSachin Sharma
Pediatric nurses play a vital role in the health and well-being of children. Their responsibilities are wide-ranging, and their objectives can be categorized into several key areas:
1. Direct Patient Care:
Objective: Provide comprehensive and compassionate care to infants, children, and adolescents in various healthcare settings (hospitals, clinics, etc.).
This includes tasks like:
Monitoring vital signs and physical condition.
Administering medications and treatments.
Performing procedures as directed by doctors.
Assisting with daily living activities (bathing, feeding).
Providing emotional support and pain management.
2. Health Promotion and Education:
Objective: Promote healthy behaviors and educate children, families, and communities about preventive healthcare.
This includes tasks like:
Administering vaccinations.
Providing education on nutrition, hygiene, and development.
Offering breastfeeding and childbirth support.
Counseling families on safety and injury prevention.
3. Collaboration and Advocacy:
Objective: Collaborate effectively with doctors, social workers, therapists, and other healthcare professionals to ensure coordinated care for children.
Objective: Advocate for the rights and best interests of their patients, especially when children cannot speak for themselves.
This includes tasks like:
Communicating effectively with healthcare teams.
Identifying and addressing potential risks to child welfare.
Educating families about their child's condition and treatment options.
4. Professional Development and Research:
Objective: Stay up-to-date on the latest advancements in pediatric healthcare through continuing education and research.
Objective: Contribute to improving the quality of care for children by participating in research initiatives.
This includes tasks like:
Attending workshops and conferences on pediatric nursing.
Participating in clinical trials related to child health.
Implementing evidence-based practices into their daily routines.
By fulfilling these objectives, pediatric nurses play a crucial role in ensuring the optimal health and well-being of children throughout all stages of their development.
CHAPTER 1 SEMESTER V PREVENTIVE-PEDIATRICS.pdfSachin Sharma
This content provides an overview of preventive pediatrics. It defines preventive pediatrics as preventing disease and promoting children's physical, mental, and social well-being to achieve positive health. It discusses antenatal, postnatal, and social preventive pediatrics. It also covers various child health programs like immunization, breastfeeding, ICDS, and the roles of organizations like WHO, UNICEF, and nurses in preventive pediatrics.
Defecation
Normal defecation begins with movement in the left colon, moving stool toward the anus. When stool reaches the rectum, the distention causes relaxation of the internal sphincter and an awareness of the need to defecate. At the time of defecation, the external sphincter relaxes, and abdominal muscles contract, increasing intrarectal pressure and forcing the stool out
The Valsalva maneuver exerts pressure to expel faeces through a voluntary contraction of the abdominal muscles while maintaining forced expiration against a closed airway. Patients with cardiovascular disease, glaucoma, increased intracranial pressure, or a new surgical wound are at greater risk for cardiac dysrhythmias and elevated blood pressure with the Valsalva maneuver and need to avoid straining to pass the stool.
Normal defecation is painless, resulting in passage of soft, formed stool
CONSTIPATION
Constipation is a symptom, not a disease. Improper diet, reduced fluid intake, lack of exercise, and certain medications can cause constipation. For example, patients receiving opiates for pain after surgery often require a stool softener or laxative to prevent constipation. The signs of constipation include infrequent bowel movements (less than every 3 days), difficulty passing stools, excessive straining, inability to defecate at will, and hard feaces
IMPACTION
Fecal impaction results from unrelieved constipation. It is a collection of hardened feces wedged in the rectum that a person cannot expel. In cases of severe impaction the mass extends up into the sigmoid colon.
DIARRHEA
Diarrhea is an increase in the number of stools and the passage of liquid, unformed feces. It is associated with disorders affecting digestion, absorption, and secretion in the GI tract. Intestinal contents pass through the small and large intestine too quickly to allow for the usual absorption of fluid and nutrients. Irritation within the colon results in increased mucus secretion. As a result, feces become watery, and the patient is unable to control the urge to defecate. Normally an anal bag is safe and effective in long-term treatment of patients with fecal incontinence at home, in hospice, or in the hospital. Fecal incontinence is expensive and a potentially dangerous condition in terms of contamination and risk of skin ulceration
HEMORRHOIDS
Hemorrhoids are dilated, engorged veins in the lining of the rectum. They are either external or internal.
FLATULENCE
As gas accumulates in the lumen of the intestines, the bowel wall stretches and distends (flatulence). It is a common cause of abdominal fullness, pain, and cramping. Normally intestinal gas escapes through the mouth (belching) or the anus (passing of flatus)
FECAL INCONTINENCE
Fecal incontinence is the inability to control passage of feces and gas from the anus. Incontinence harms a patient’s body image
PREPARATION AND GIVING OF LAXATIVESACCORDING TO POTTER AND PERRY,
An enema is the instillation of a solution into the rectum and sig
2. Overview
Introduction
Production, transport and conversion of thyroid
hormones
Regulation of thyroid hormones
Mechanism of Action and actions of thyroid
hormones
Effect of thyroid hormone on various systems
Hypo and hyperthyroidism
Summary
3. Introduction - Thyroid Gland
The thyroid gland, located immediately
below the larynx on each side of and anterior
to trachea, is one of the largest of endocrine
glands.
It secretes two major hormonesThyroxine
and triidothyronine.
It also secretes calcitonin, an important
hormone for calcium meatabolism
4.
5. Introduction - Thyroid Hormones
There are two biologically active thyroid hormones:
- tetraiodothyronine (T4; usually called thyroxine)
- triiodothyronine (T3)
Derived from modification of tyrosine.
6. Differences between T4 and T3
The thyroid secretes about 80 microg ofT4, but only
5 microg ofT3 per day.
However,T3 has a much greater biological activity
(about 10 X) thanT4.
T4
thyroid
I-
T3
7. Importance of Iodine
• Thyroid hormones are unique biological
molecules in that they incorporate iodine in their
structure.
• Thus, adequate iodine intake (diet, water) is
required for normal thyroid hormone production.
• Major sources of iodine:
- iodized salt
- iodated bread
- dairy products
- shellfish
• Minimum requirement: 75 micrograms/day
8. Iodine Metabolism
• Dietary iodine is absorbed in the GI tract, then
taken up by the thyroid gland.The basal
membrane of the thyroid cell has the specific
ability to pump iodine actively to the interior of
the cell.This is called iodide trapping.
• Iodide taken up by the thyroid gland is oxidized
by peroxide in the lumen of the follicle:
peroxidas
eI- I+
• Oxidized iodine can then be used in production of
thyroid hormones.
9. Production of Thyroglobulin
Pituitary producesTSH, which binds to follicle
cell receptors.
The follicle cells of the thyroid produce
thyroglobulin.
Thyroglobulin is released into the colloid
space, where it’s tyrosine residues are iodinated
by I+.
This results in tyrosine residues which have one
or two iodines attached (monoiodotyrosine or
diiodotyrosine).
10. More and more of iodotyrosine residues
become coupled with one another. The major
production of this coupling reaction is
thyroxine molecule.
One molecule of monoiodotyrosine couples
with diidotyrosine to form tridotyrosine
(T3).
11. Transport of Thyroid Hormones
• Thyroid hormones are not very soluble in water (but are
lipid-soluble).
• Thus, they are found in the circulation associated with
binding proteins:
-Thyroid Hormone-Binding Globulin (~70% of hormone)
- Pre-albumin (transthyretin), (~15%)
-Albumin (~15%)
• Less than 1% of thyroid hormone is found free in the
circulation.
• Only free and albumin-bound thyroid hormone is
biologically available to tissues.
12. Conversion of T4 to T3
T3 has much greater biological activity thanT4.
A large amount ofT4 (25%) is converted toT3 in
peripheral tissues.
This conversion takes place mainly in the liver and
kidneys. TheT3 formed is then released to the blood
stream.
In addition toT3, an equal amount of “reverseT3”
may also be formed. This has no biological activity.
13. The thyroid gland is capable of storing many
weeks worth of thyroid hormone (coupled to
thyroglobulin).
If no iodine is available for this period, thyroid
hormone secretion will be maintained.
Storage of thyroglobulin
14. Regulation of Thyroid Hormone
Levels
Thyroid hormone synthesis and secretion is
regulated by two main mechanisms:
- an “autoregulation” mechanism, which
reflects the available levels of iodine
- Neuroendocrine regulation by the
hypothalamus and anterior pituitary
15. Autoregulation of Thyroid Hormone
Production
The rate of iodine uptake and incorporation into
thyroglobulin is influenced by the amount of
iodide available:
- low iodide levels increase iodine transport into
follicular cells
- high iodide levels decrease iodine transport into
follicular cells
Thus, there is negative feedback regulation of
iodide transport by iodide.
16. Neuroendocrine Regulation of
Thyroid Hormones: Role of TSH
Thyroid-stimulating hormone (TSH) is produced by
thyrotroph cells of the anterior pituitary.
TSH is a glycoprotein hormone composed of two
subunits:
- alpha subunit (common to LH, FSH,TSH)
-TSH beta subunit, which gives specificity of receptor
binding and biological activity
17. Action of TSH on the Thyroid
TSH acts on follicular cells of the thyroid.
- increases iodide transport into follicular cells
- increases production and iodination of
thyroglobulin
- increases endocytosis of colloid from lumen into
follicular cells
Na+
I-
thyroglobulinfollicle
cell
gene
I-
endocytosis
thyroglobulin
T3 T4
colloid droplet
I-I+
iodination
thyroglobulin
Na+ K+
ATP
18. Regulation of TSH Release from
the Anterior Pituitary
TSH release is influenced by hypothalamicTRH, and
by thyroid hormones themselves.
Thyroid hormones exert negative feedback onTSH
release at the level of the anterior pituitary.
- inhibition ofTSH synthesis
- decrease in pituitary receptors forTRH
hypothalamus
TRH
TRH receptor
TSH synthesis
pituitary T3/T4
+
-
-
19. Influence of TRH on TSH Release
• Thyrotropin-releasing hormone (TRH) is a
hypothalamic releasing factor which travels through
the pituitary portal system to act on anterior
pituitary thyrotroph cells.
TRH phospholipase C
G protein-coupled
receptor
IP3 calcium
DAG PKC
calmodulin
• Thyroid hormones also inhibit TRH synthesis.
20. Negative Feedback Actions of
Thyroid Hormones on TSH Synthesis
and Release
hypothalamus
TRH
TRH receptor
TSH synthesis
pituitary
T3/T4
+
-
-
-
TRH synthesis
Thyroid gland
follicle cell receptors
TSH binds
21. Other Factors Regulating Thyroid
Hormone Levels
Diet: a high carbohydrate diet increasesT3
levels, resulting in increased metabolic rate (diet-
induced thermogenesis).
Low carbohydrate diets decreaseT3
levels, resulting in decreased metabolic rate.
Cold Stress: increasesT3 levels in other
animals, but not in humans.
Any condition that increases body energy
requirements (e.g., pregnancy, prolonged cold)
stimulates hypothalamus TRH TSH (Pit)
22. Mechanism of Action of Thyroid
hormones
The general effect of thyroid hormone is to
activate nuclear transcrpition of large numbers
of genes.
Therefore in virtually all cells of the body, great
numbers of protein enzymes, structural
proteins, transport proteins are synthesized.
The net result is generalized increase in
functional activity throughout the body.
23. T3/T4 acts through the thyroid hormone
receptor, which are attached to the DNA.
When not bound to hormone, the thyroid
hormone receptor binds to target DNA. It
is associated with corepressor proteins
that cause DNA to be tightly wound and
inhibit transcription.
Binding of hormone causes a
conformational change, resulting in loss of
corepressor binding and association with
coactivator proteins, which loosen DNA
structure and stimulate transcription.
24. One Major Target Gene of T3: The
Na+/K+ ATPase Pump
Pumps sodium and potassium across cell
membranes to maintain resting membrane potential
Activity of the Na+/K+ pump uses up energy, in the
form of ATP
About 1/3rd of all ATP in the body is used by the
Na+/K+ ATPase
T3 increases the synthesis of Na+/K+
pumps, markedly increasing ATP consumption.
T3 also acts on mitochondria to increase ATP
synthesis
The resulting increased metabolic rate increases
thermogenesis (heat production).
25. Actions of Thyroid Hormones
Thyroid hormones are essential for normal
growth of tissues, including the nervous system.
Lack of thyroid hormone during development
results in short stature and mental deficits
(cretinism).
Thyroid hormone stimulates basal metabolic
rate.
26. Effects of Thyroid Hormone on
Nutrient Sources
• Effects on protein synthesis and degradation:
-increased protein synthesis at low thyroid
hormone levels (low metabolic rate; growth)
-increased protein degradation at high thyroid
hormone levels (high metabolic rate; energy)
• Effects on carbohydrates:
-low doses of thyroid hormone increase glycogen
synthesis (low metabolic rate; storage of energy)
- high doses increase glycogen breakdown (high
metabolic rate; glucose production)
27. Thyroid Hormone Actions
which Increase Oxygen
Consumption
Increase mitochondrial size, number and key
enzymes
Increase plasma membrane Na-K ATPase
activity
Increase futile thermogenic energy cycles
Decrease superoxide dismutase activity
28. Effects of Thyroid Hormones
on the Cardiovascular System
Increase heart rate
Increase force of cardiac contractions
Increase stroke volume
Increase Cardiac output
Up-regulate catecholamine receptors
29. Effects of Thyroid Hormones
on the Respiratory System
Increase resting respiratory rate
Increase minute ventilation
Increase ventilatory response to hypercapnia
and hypoxia
30. Effects of Thyroid Hormones
on the Renal System
Increase blood flow
Increase glomerular filtration rate
31. Effects of Thyroid Hormones
on Oxygen-Carrying Capacity
Increase RBC mass
Increase oxygen dissociation from
hemoglobin
32. Effects of Thyroid Hormones
on Intermediary Metabolism
Increase glucose absorption from the GI tract
Increase carbohydrate, lipid and protein
turnover
Down-regulate insulin receptors
Increase substrate availability
33. Effect of Thyroid Hormone on growth
Required for GH and prolactin production and
secretion, Required for GH action
Increases intestinal glucose reabsorption (glucose
transporter)
Increases mitochondrial oxidative
phosphorylation (ATP production)
Increases activity of adrenal medulla
(sympathetic; glucose production)
Induces enzyme synthesis
Result: stimulation of growth of tissues and
increased metabolic rate. Increased heat
production (calorigenic effect)
34. Effects Thyroid Hormones in
Growth and Tissue
Development
Increase growth and maturation of bone
Increase tooth development and eruption
Increase growth and maturation of
epidermis,hair follicles and nails
Increase rate and force of skeletal muscle
contraction
Inhibits synthesis and increases degradation of
mucopolysaccharides in subcutaneous tissue
35. Effects of Thyroid Hormones
on the Nervous System
Critical for normal CNS neuronal
development
Enhances wakefulness and alertness
Enhances memory and learning capacity
Required for normal emotional tone
Increase speed and amplitude of peripheral
nerve reflexes
36. Effects of Thyroid Hormones
on the Reproductive System
Required for normal follicular development
and ovulation in the female
Required for the normal maintenance of
pregnancy
Required for normal spermatogenesis in the
male
37. Thyroid Hormone Deficiency:
Hypothyroidism
Early onset: delayed/incomplete physical and
mental development
Later onset (youth): Impaired physical growth
Adult onset (myxedema) : gradual changes
occur. Tiredness, lethargy, decreased metabolic
rate, slowing of mental function and motor
activity, cold intolerance, weight
gain, goiter, hair loss, dry skin. Eventually may
result in coma.
Many causes (insufficient iodine, lack of thyroid
gland, lack of hormone receptors, lack ofTH
binding globulin)
38. Hypothyroidism and Goiter
During iodine
deficiency, thyroid
hormone production
decreases.
This results in increased
TSH release (less
negative feedback).
TSH acts on
thyroid, increasing blood
flow, and stimulating
follicular cells and
increasing colloid
production.
39. Thyroid Hormone Excess:
Hyperthyroidism
Emotional symptoms
(nervousness, irritability), fatigue, heat
intolerance, elevated metabolic rate, weight
loss, tachycardia, goiter, muscle
wasting, apparent bulging of eyes, may develop
congestive heart failure.
Also due to many causes (excessiveTSH
release, autoimmune disorders,)
40.
41. Cretinism
Cretinism is caused by extreme
hypothyroidism during fetal life, infancy, or
childhood. Commonly due to Congenital lack
of thyroid gland or failure of gland to produce
hormone due to genetic defect.
This condition Is characterized by failure of
body growth and mental retardation
42. A neonate without a thyroid gland may have
normal appearance as it was supplied with
thyroid hormones by the mother in utero.
But within a few weeks neonates movements
become sluggish and growth begin to be
greatly retarded.
Treatment with adequate iodine or thyroxine
usually causes return to normal growth. But
unless it is treated within a few weeks after
birth mental retardation becomes
permanent.
43. Thyroid hormones:
Key Points
• Held in storage
• Bound to mitochondria, thereby increasing ATP
production
• Bound to receptors activating genes that control
energy utilization
• Exert a calorigenic effect
44. References
Textbook of Medical Physiology 11th edition
by GUYTON & HALL
Principals of Pharmacology by BENNET &
BROWN.