Which class of hormones is characterized by water-soluble solubility, no carrier, and a half-life of about 10-30 minutes?

• A. Proteins
• B. Glycopeptides
• C. Steroids
• D. Amines/Tyrosine-derived

Answer: (A)

Water-soluble peptide/protein hormones travel in the blood as free, unbound molecules and act by binding receptors on the surface of target cells, triggering signaling cascades rather than entering the cell. Because they are hydrophilic, they don’t need carrier proteins to circulate. Their lifetimes in the circulation are relatively short, typically on the order of minutes to a few tens of minutes, which aligns with a half-life around 10–30 minutes. This combination—soluble in plasma, no carrier required, and a moderate short half-life—fits protein hormones well.

Steroid hormones, in contrast, are lipid-soluble and rely on carrier proteins in the blood, often giving them longer half-lives. Amine derivatives from tyrosine (like catecholamines) are also water-soluble but have much shorter half-lives, usually only a few minutes. Glycopeptides are a subset of protein hormones, but the broader and most inclusive class that matches the described properties is proteins.