Which type of hormones are hydrophilic and soluble in the blood?

Peptide hormones are indeed hydrophilic and soluble in blood, which is a crucial characteristic of these types of hormones. Being hydrophilic allows peptide hormones to readily dissolve in the aqueous environment of the bloodstream, enabling them to be transported easily to target tissues and organs.

Peptide hormones are composed of chains of amino acids and generally include hormones such as insulin, glucagon, and growth hormone. Because of their solubility, they interact with receptors on the surface of target cells, triggering a series of intracellular signaling cascades without needing to pass through the cell membrane. This mechanism contrasts with fat-soluble hormones, such as steroid hormones, which require carrier proteins for transport in the bloodstream and typically act on intracellular receptors.

The hydrophilic nature of peptide hormones is important for their fast action and relatively short half-lives in the circulation, making them capable of eliciting rapid physiological responses. This property distinguishes them from other hormone types that may require different transport mechanisms or cellular entry strategies.