Hormone Classification and Derivatives

Hormone Classification

• Hormones are classified based on their proximity to the site of action (autocrine, paracrine, endocrine, neuroendocrine, pheromones) and chemical structure (proteins/peptides, steroids, amino acid derivatives, eicosanoids).
• Hormones with different chemical structures have different solubilities in aqueous media (hydrophobic or hydrophilic).

Hormone Derivatives of Tyrosine and Tryptophan

• Hormones are derived from the amino acids tyrosine and tryptophan.
• Examples of hormones derived from tyrosine include dopamine, noradrenaline, adrenaline. These are catecholamines.
• Examples of hormones derived from tryptophan include serotonin and melatonin.

Hormone Derivatives of Tryptophan - Detailed Pathway

• L-Tryptophan is the precursor.
• Tryptophan-5-hydroxylase converts L-Tryptophan to 5-Hydroxytryptophan
• 5-Hydroxytryptophan decarboxylase creates Serotonin
• Serotonin N-acetyltransferase (NAT) creates N-acetylserotonin
• Hydroxindole-0-methyltransferase converts N-acetylserotonin to melatonin.

Melatonin - Actions and Functions

• Melatonin has various actions including:
• Anti-inflammatory function
• Anti-oxidative function
• Immunomodulation
• Cardioprotection
• Neuroprotection
• Melanogenesis controller
• Metabolism regulator
• Fixing sleep dysfunction
• Circadian rhythm modulator
• Antineoplastic properties

Hormone Derivatives of Tyrosine - Detailed Pathway

• Tyrosine is the precursor.
• Tyrosine is converted to Dopa
• Dopa is converted to Dopamine
• Dopamine is converted to Noradrenaline
• Noradrenaline is converted to Adrenaline

Protein or Peptide Hormones

• Protein or peptide hormones consist of shorter chain peptides, larger proteins, and glycoproteins.

Peptide Hormone Example - Oxytocin

• Oxytocin is a peptide hormone
• Its structure is displayed in a diagram

Protein Hormone Example - Growth Hormone

• Growth hormone is a protein hormone.
• Its structure is displayed in a diagram

Glycoprotein Hormones - Structure and Subunits

• Glycoprotein hormones are a family of protein hormones with alpha and beta subunits.
• The alpha subunit is typically common.
• The beta subunit determines the specificity of the hormone.
• Examples include TSH, LH, EPO, hCG, and Inhibin

Lipid Derived Hormones - Cholesterol Derived Steroids

• These hormones are derived from cholesterol, and enzymes are located in mitochondria and the smooth ER.
• They are lipid soluble and are immediately released; they are not stored in cells.
• Examples include:
  • Gonadal steroids (androgens, estrogens, progestins)
  • Adrenocortical steroids (glucocorticoids like cortisol, mineralocorticoids like aldosterone)

Lipid Derived Hormones - Eicosanoids

• Eicosanoids are oxygenated fatty acids derived from either omega-3 or omega-6 fatty acids.
• They are lipid mediators.
• Subfamilies include prostaglandins (PGs), thromboxanes, and leukotrienes.

Chemical Structure Determines Hormone Properties

• Chemical structure influences the hormone's:
  • Synthesis, Storage, Release
  • Transport in Body Fluids
  • Receptor Location
  • Mechanism of Action
  • Degradation

Hormone Synthesis and Storage - Protein/Peptide Hormones

• Protein/peptide hormones are synthesized in steps.
• These hormones are synthesized within the cell, then packaged into vesicles.
• Released on demand (by exocytosis from cells), and stored within the cell until needed.

Steps in Making a Protein/Peptide Hormone

• The process starts with gene transcription
• It moves through primary RNA transcription to post-transcriptional modification
• Moving through Messenger RNA to Prepeptide/Prepropeptide
• Followed by translation, post-translational modification
• Lastly, secretion of the mature (active) peptide hormone

Mechanisms of Protein Hormone Synthesis and Release

• Hormones are produced, processed and packaged in vesicles for release.
• Exocytosis of the hormones from cells results in proper hormone release

Hormone Synthesis and Storage - Steroid Hormones

• Steroid hormones are derived from cholesterol.
• Synthesized and immediately released, and not packaged into vesicles prior to release.
• Enzymes are found in the mitochondria and smooth endoplasmic reticulum

Steroid Hormone Synthesis Pathways

• The process displays a variety of chemical transformations of steroid hormones, from cholesterol through various intermediates to different steroids like testosterone and estrogen.

Steroids and Target Cell Activation

• Steroids are transformed to active steroids in target cells.
• Steroid hormones enter the target cells, where they bind to intracellular receptors, then enter the nucleus and affect gene expression.

Protein/Peptide vs Steroid Secreting Cells

• Diagram shows the differences in cellular structures of protein/peptide secreting cells versus steroid secreting cells.
• Different machinery and cellular features are shown in the diagrams to illustrate how hormones are synthesized, stored, and released appropriately using those systems.

Explore the classification of hormones based on their site of action and chemical structure. Dive deep into the derivatives of tyrosine and tryptophan, learning about key hormones like dopamine, serotonin, and melatonin. This quiz will enhance your understanding of hormonal pathways.