BIOS5130 Week 8 Slides (1)

Week 8 Lecture Overview

Introduction

• Focus on the endocrine system, which plays a crucial role in regulating various bodily functions through hormones.

• Presented by Dr. Emma Hargreaves, an expert in the field of endocrinology.

Subject Specific Learning Outcomes

• Understand the structural organization and function of body systems, particularly how they differ and interconnect.

• Recognize integrated actions of body systems that contribute to homeostasis, the body's ability to maintain stable internal conditions despite external changes.

• Identify causes of diseases due to system malfunctions, using specific examples to illustrate these concepts.

• Appreciate the interrelation between physiology, anatomy, and medicine, understanding how they work together to influence health and disease.

Module Information

Convenors and Teachers

• Module Convenor: Dr. Emma Hargreaves

• Module Teachers:

  • Prof. John Dickinson

  • Dr. Sam Smith

  • Dr. Peter Ellis

Weekly Structure

• Week 8: Focus on Endocrinology with Dr. Emma Hargreaves.

• Week 9-13: Transition into the Nervous System under the guidance of Dr. Emma Hargreaves.

• Week 15-16: Explore the Kidneys with in-depth insights from Dr. Emma Hargreaves.

• Week 17-18: Study Muscle physiology with contributions from Prof. John Dickinson and Dr. Sam Smith.

• Week 19: Discuss Reproductive physiology with Dr. Peter Ellis.

• Workshops: Scheduled for Week 11 or 13, focusing on problem-solving practice (compulsory).

Assessments

• Problem-solving test scheduled for Week 15 to assess application of knowledge.

• 2-hour final exam covering comprehensive course content.

• Feedback on assessments will be provided in Week 16 to aid in understanding and improvement.

Essential Textbook

• Title: Human Physiology: An Integrated Approach

• Author: Dee Unglaub Silverthorn (8th Global Edition)

• Recommended for students to obtain a personal copy, with library resources also available for reference.

Endocrinology Overview

Hormones

• Definition: Hormones are chemical messengers secreted into the bloodstream that can have widespread effects on distant tissues throughout the body, coordinating complex processes such as growth, metabolism, and mood.

Functionality:

• Hormones bind to specific receptors located in cell membranes, the cytoplasm, or the nucleus, and initiate a cascade of cellular responses even at very low concentrations (nanomolar/picomolar levels).

Effects on Target Cells:

• Hormones can influence:

  • Enzyme reaction rates, promoting or inhibiting metabolic pathways.

  • Transport regulation across cellular membranes, ensuring the appropriate uptake or expulsion of substances.

  • Gene expression regulations, affecting how cells respond to various stimuli.

Hormone Classification

Part 1: Hormones Overview

• Pineal Gland: Produces Melatonin, which regulates sleep-wake cycles (circadian rhythms).

• Hypothalamus: Releases various hormones that either stimulate or inhibit the anterior pituitary's function, contributing to the body’s hormonal responses.

• Posterior Pituitary: Releases Oxytocin (important for childbirth and lactation) and Vasopressin (important for water retention and blood pressure regulation).

Part 2: Additional Hormones

• Anterior Pituitary: Produces hormones like Prolactin (stimulates milk production), Growth Hormone (GH) (stimulates growth), and Adrenocorticotropic Hormone (ACTH) (regulates cortisol release during stress).

• Thyroid: Produces Triiodothyronine and Thyroxine, which are critical for metabolic rate regulation.

• Adrenal Cortex: Produces Cortisol (stress response) and Aldosterone (regulates blood pressure and electrolyte balance).

Part 3: Reproductive Hormones

• Ovaries: Produce Estrogens and Progesterone, essential for ovulation and secondary sexual characteristics in females.

• Testes: Produce Androgens (mainly testosterone) and Inhibin, which play key roles in sperm production and male secondary sexual characteristics.

Hormone Interactions

• Synergistic: The combined effects of two or more hormones amplify the response beyond what they would achieve alone.

• Permissive: One hormone must be present for another hormone to exert its full effect.

• Antagonistic: Some hormones have opposing functions, such as insulin (lowers blood sugar) vs. glucagon (raises blood sugar).

Hormone Classifications Comparison

• Peptide Hormones: Synthesized as inactive forms (prohormones), stored in vesicles, and released via exocytosis, initiating signal transduction through second messengers.

• Steroid Hormones: Derived from cholesterol, they pass through cell membranes and bind to intracellular receptors, directly affecting gene transcription and protein synthesis.

• Amine Hormones: Mostly derived from the amino acid tyrosine, these hormones can act through membrane-bound receptors or penetrate the nucleus.

Regulation of Hormone Release

• Reflex pathways and feedback loops govern hormone release.

• Simple Reflexes: Single stimulus leading to hormone secretion (e.g., parathyroid hormone in response to low calcium levels).

• Complex Reflexes: Involved in integrating multiple stimuli, hormones, or responses (e.g., the hypothalamic-pituitary pathway, coordinating numerous endocrine responses).

Endocrine Reflexes

• Simple Reflex Example: The secretion of parathyroid hormone increases in response to decreased blood calcium levels to restore balance.

• Multiple Stimuli: For example, insulin release is influenced by blood glucose levels, food intake, and responses from intestinal peptides.

• Hypothalamic-Pituitary pathway: Represents a hierarchical system where feedback signals can influence multiple levels of hormone regulation.

Endocrine Disorders

Types of Dysfunction

• Hypersecretion: Increased hormone levels leading to exaggerated biological responses (e.g., Cushing's Syndrome caused by excess cortisol).

• Hyposecretion: Insufficient hormone production resulting in underactive physiological processes (e.g., Addison's Disease characterized by insufficient cortisol levels).

• Receptor Defects: Changes in responsiveness to hormones can lead to conditions such as pseudohypoparathyroidism, where the target tissues do not respond adequately to parathyroid hormone.

Graves' Disease Case Study

Overview

• Condition: An autoimmune disorder leading to hyperthyroidism, where the immune system mistakenly attacks the thyroid gland.

Symptoms

• Common symptoms include emotional swings, weight loss, increased heart rate (palpitations), and the presence of a goiter (enlarged thyroid).

Causes

• The condition is characterized by the production of thyroid antibodies that stimulate excess thyroid hormone production.

Treatments

• Therapeutic strategies include the use of drugs to inhibit iodine uptake, radioactive iodine therapy to ablate thyroid tissue, and potentially surgical removal of the thyroid gland if necessary.

Learning Outcomes

• Understand the sources of various hormones and their physiological functions.

• Compare the three major classes of hormones concerning synthesis pathways and signaling mechanisms.

• Comprehend how hormone release is regulated through both simple and complex reflex pathways.

• Analyze the causes of endocrine disorders and their diagnostic implications for clinical practice.

Endocrine Condition Diagnosis The patient is most likely to be diagnosed with Graves' Disease, an autoimmune disorder that leads to hyperthyroidism, characterized by the overproduction of thyroid hormones.

Pathophysiological Basis:

• Autoimmune Response: The condition arises when the immune system produces antibodies (thyroid-stimulating immunoglobulins) that stimulate the thyroid gland to produce excessive amounts of thyroid hormones (T3 and T4).

• Symptoms: This excess hormone production leads to increased metabolic activity, resulting in symptoms such as unexplained weight loss, palpitations, sweating, hand tremors, and insomnia. The bulging eyes (exophthalmos) and possible goitre are due to enlarged thyroid tissue and the accumulation of glycosaminoglycans in the orbit and thyroid.

Diagnostic Approaches:

1. Blood Tests: Checking levels of TSH (Thyroid Stimulating Hormone), T3, and T4. In Graves' Disease, TSH is typically low and T3/T4 are elevated.

2. Thyroid Antibody Tests: Measuring the concentration of thyroid-stimulating immunoglobulins (TSIs) can confirm the autoimmune nature of the disease.

3. Thyroid Scan: A radioactive iodine uptake test can assess the functional status of thyroid tissue, showing diffuse hyperactivity typical of Graves' Disease.

Therapeutic Interventions:

1. Antithyroid Medications: Drugs like methimazole or propylthiouracil can reduce thyroid hormone production by inhibiting the enzyme thyroid peroxidase.

2. Radioactive Iodine Therapy: This treatment involves administering radioactive iodine, which selectively ablates overactive thyroid tissue, thereby reducing hormone production.

3. Surgery: In some cases, particularly when there is a large goitre or suspicion of malignancy, surgical removal of part or all of the thyroid may be indicated.

4. Beta-Blockers: These may be prescribed to manage symptoms such as palpitations and anxiety during the initial treatment