Endocrinology Lecture Notes

LO

1. Describe the various types of chemical 'inter-cellular messenger' in the body.
2. Describe and distinguish the basic structure, synthesis, release, transport and mechanism of hormone action of a) peptide, and b) steroid hormones.
3. Explain the physiological mechanisms involved in the regulation of hormone release, including feedback control, the endocrine axis, neuroendocrine reflexes and diurnal rhythms.
4. Briefly summarise the types of endocrine disorders and the principles of treatment of these conditions.

Hard shiz

• neuroendocrine reflexes and diurnal rythms
• the types of treatments for the disorders

Introduction

• Lecturer: Sue Chan
• Topic: Endocrinology
• Schedule: 3 lectures this semester and another 3 next semester
• Focus: Endocrine system and hormones in the body

Lecture Overview

• Main Concepts:
  • Hormone mechanisms
  • Endocrine glands and systems
  • Hormone synthesis, transport, and action
  • Endocrine disorders and diseases

Key Terminology

• Endocrine: Internal secretion; glands secrete hormones into the bloodstream.
• Exocrine: External secretion; glands with ducts (e.g., salivary glands) secrete outside the body.
• Hormones: Chemical messengers for intercellular communication.

Types of Intercellular Messengers

• Endocrine: Hormones secreted into bloodstream, travel to distant targets (e.g., Insulin).
• Autocrine: Substance affects the same cell that secreted it (e.g., Prostaglandins).
• Paracrine: Substance affects neighboring cells (e.g., Somatostatin affecting insulin secretion).
• Neuroendocrine: Nerve cells that secrete hormones into the blood (e.g., Oxytocin, ADH).
• Neurotransmitters: Secreted by neurons, cross synapses (e.g., Acetylcholine).

Types of Hormones

• Peptide Hormones: Chains of amino acids, hydrophilic (e.g., TRH, LH, FSH).
• Steroid Hormones: Lipophilic, derived from cholesterol (e.g., Cortisol, testosterone).
• Tyrosine-derived Hormones: Include thyroid hormones and catecholamines (e.g., Adrenaline).

Hormone Synthesis and Release

• Peptide Hormones:
  • Synthesized as pre-prohormones, processed in RER and Golgi apparatus.
  • Stored in secretory granules, released by exocytosis.
• Steroid Hormones:
  • Derived from cholesterol, synthesized through enzymatic conversion.
  • Not stored, diffuse out of the cell and transported bound to plasma proteins.

Transport and Action

• Peptide Hormones:
  • Transported freely in the blood, short half-life due to protease activity.
  • Receptors on plasma membrane, signal through G-proteins or tyrosine kinases.
• Steroid Hormones:
  • Bound to plasma proteins, longer half-life.
  • Intracellular receptors, affect gene expression (genomic effects).

Regulation of Hormone Release

• Feedback Mechanisms:
  • Negative Feedback: Maintains homeostasis by inhibiting processes when levels are too high.
  • Positive Feedback: Rare, amplifies processes, not related to homeostasis.
• Endocrine Axis: Includes hypothalamus, pituitary, and target glands with multiple feedback loops.
• Neuroendocrine Reflexes: Higher brain centers influence hormone release (e.g., cortisol).
• Diurnal and Circadian Rhythms: Hormone levels fluctuate with daily cycles (e.g., cortisol).

Endocrine Disorders

• Causes:
  • Hypersecretion: Excess hormone production.
  • Hyposecretion: Deficiency in hormone production.
  • Decreased Responsiveness: Target cells are less responsive to hormones.
• Primary vs Secondary Causes:
  • Primary: Issue with the gland that produces the hormone.
  • Secondary: Due to external factors or upstream endocrine issues.
• Examples: Cushing's syndrome (excess cortisol).

Treatment Strategies

• Hormone Replacement: For deficiencies.
• Inhibiting Excess Hormone Production: Via drugs or receptor blockers.
• Enhancing Cellular Response: Where responsiveness is decreased.
• Tumor Treatment: Locate and remove tumors if related to hormone issues.

Next Class: 10:05 AM, break for 10 minutes.