Hormone Classification (Peptides, Steroids, Amines)
Start with the big picture
Peptide hormones are generally hydrophilic, stored in secretory vesicles, and released by Ca²⁺-dependent exocytosis. They circulate largely unbound and act through plasma-membrane receptors that trigger second-messenger pathways, typically producing rapid, short-lived effects. Steroid hormones are lipophilic cholesterol derivatives made on demand; they travel mainly bound to plasma proteins and act through intracellular receptors that regulate gene transcription, giving slower, prolonged effects. Amine hormones show both patterns: catecholamines signal through membrane receptors, thyroid hormones act through nuclear receptors, and melatonin signals through GPCRs. The central comparison is not simply the hormone’s class name, but the relationship among solubility, storage, transport, receptor location, and signaling mechanism.
What you'll learn
- Compare peptide, steroid, and amine hormones by solubility, synthesis, storage, and transport.
- Describe how peptide hormones are secreted and activate membrane-associated signaling pathways.
- Explain how steroid receptors influence gene transcription and contribute to prolonged hormone action.
- Distinguish catecholamine, thyroid hormone, and melatonin signaling patterns.
- Relate receptor location and signaling type to differences in hormone-action timing.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
