Carrier proteins bind with specific solutes and transfer them across the lipid bilayer.
Carrier proteins undergo conformational changes that expose the solute-binding site on one side of the membrane and then on the other.
The role of carrier proteins in hormones:
Steroid and thyroid hormones increase the solubility of hydrophobic compounds in the plasma.
Peptide hormones prevent the destruction by the enzyme named proteases in the plasma.
The small hydrophilic amino acids which were derived from hormones prevent filtration by the kidneys.
Carrier proteins deliver the hormones to their target cells and protect them from being chemically changed, inactivated, and eliminated from the body by the liver and kidneys.