Which of the following statements is correct regarding the signaling mechanism of hydrophilic hormones?

The signaling mechanism of hydrophilic hormones indeed relies on the use of second messengers. These hormones are generally unable to cross cell membranes due to their water-solubility and therefore bind to specific receptors located on the surface of target cells. Once bound, this binding activates intracellular signaling cascades, typically involving secondary messengers like cyclic AMP (cAMP) or calcium ions. These second messengers then propagate the signal within the cell, leading to a physiological response.

This mechanism is distinct from that of hydrophobic hormones, which can pass directly through the cell membranes and often bind to intracellular or nuclear receptors, directly influencing gene expression. Consequently, the reliance on second messengers highlights the complexity of signaling pathways mediated by hydrophilic hormones, facilitating a rapid and broad range of physiological effects without the need for direct cellular entry.