Endocrine System Overview

Objectives of the Endocrine System

• Understanding Hormones

  • Functions of hormones

  • Major structures of the endocrine system

  • Hormones produced and their targets

• Interaction with Targets

  • Mechanisms of hormone interaction with target cells

  • Pathologies arising from endocrine system dysfunction

• Histology Identification

  • Ability to identify thyroid histology slides

• Learning Objective

  • Understanding major structures of the endocrine system

• Bloom's Taxonomy

  • Remember category requiring recall of information

• Difficulty Rating

  • Rated at Difficulty 3 (requires memorization)

Key Terms in Endocrinology

• Endocrine Terms and Definitions

  • Hormone: Chemicals produced by glands regulating body functions

  • Ductless Glands: Secrete hormones directly into blood

  • Exocrine Glands: Secrete products into ducts

  • Receptors and Responses:

  • Hormones binding to cell receptors to elicit a response

  • Second messenger system involvement

• Feedback Mechanisms

  • Negative feedback: Stimulus initiates a process that inhibits the original stimulus

  • Positive feedback: Prominent in childbirth (oxytocin release during labor)

Overview of the Endocrine System

• Functionality:

  • Composed of ductless glands; synthesize and release hormones

  • Regulates development, growth, metabolism, homeostasis, digestion, and reproductive activities

Major Endocrine Glands and Their Functions

1. Pituitary Gland:

   • Master gland controlling various physiological processes

2. Thyroid Gland:

   • Produces hormones regulating metabolism and growth (e.g., T3, T4)

3. Adrenal Glands:

   • Cortex produces steroid hormones

   • Medulla produces epinephrine/norepinephrine

4. Pancreas:

   • Insulin and glucagon regulation

5. Parathyroid Glands:

   • Regulate blood calcium levels

6. Pineal Gland:

   • Secretes melatonin regulating sleep cycles

Hormone Disorders

• Growth Hormone Disorders:

  • Dwarfism: Growth hormone deficiency

  • Gigantism: Excess growth hormone

  • Acromegaly: Growth hormone excess in adults leading to abnormal bone widening

• Thyroid Hormone Disorders:

  • Hyperthyroidism: Excessive TH, e.g., Graves disease

  • Hypothyroidism: Low TH leading to various metabolic issues

• Adrenal Cortex Disorders:

  • Cushing's Syndrome: High glucocorticoid levels causing various health issues

  • Addison's Disease: Insufficient glucocorticoids leading to weight loss and fatigue

• Diabetes Mellitus:

  • Type 1: Absent insulin release

  • Type 2: Insulin resistance

  • Gestational: Develops during pregnancy

Histology in Endocrinology

• Thyroid Gland:

  • Contains follicles storing thyroglobulin

  • Parafollicular cells secrete calcitonin

• Parathyroid Glands:

  • Contain chief cells synthesizing parathyroid hormone (PTH)

• Pancreatic Islets:

  • Alpha cells produce glucagon, Beta cells produce insulin

Feedback Regulation in Endocrine Secretion

• Negative Feedback Loops: Common method for endocrine regulation

  • Short and long feedback loops depending on source of negative feedback

• Exceptions: Some hormones operate under positive feedback mechanisms, particularly during childbirth (e.g., oxytocin)

Summary of Functions and Interactions within the Endocrine System

• Hormones coordinate various systems across the body through feedback mechanisms ensuring homeostasis, growth, metabolism, and reproductive health. Understanding this complex network is critical for identifying and treating endocrine disorders effectively.

Studying Tips

• Focus on the structure-function relationship of hormones and glands.

• Familiarize with key terms, their definitions, and physiological roles.

• Practice creating and answering questions related to the objectives.