Why insulin acts in seconds and cortisol takes hours to do anything at all: peptide hormones are water-soluble and stuck outside the cell, triggering a receptor cascade that amplifies an existing signal, while steroid hormones slip straight through the membrane and rewrite gene transcription directly. Two chemistries, two mechanisms, and a speed difference that isn't incidental — it's the direct consequence of solubility.
Hormones
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Peptide Hormones vs Steroid Hormones: Two Signaling Systems, Two Different Speeds