Final answer:
The levels of carrier proteins can affect the levels of hormone activity, as these proteins influence several aspects, including the hormone's half-life, distribution, and availability to target tissues.
Step-by-step explanation:
The statement that the levels of carrier proteins doesn't affect the levels of active peptide hormones is false. Peptide hormones circulate in the blood primarily in a free form, but the presence of carrier proteins can impact their availability and activity. For example, steroid and thyroid hormones, which are different from peptide hormones, are transported bound to specific carrier proteins, like Thyroxine binding globulin (TBG). These carrier proteins can influence the hormone's half-life, its distribution, the amount of hormone that is free and active, and its access to target tissues.
Moreover, carrier proteins protect these hormones from premature degradation and excretion, meaning that changes in levels of carrier proteins can indeed have an impact on hormone levels and activity. In the case of peptide hormones, while they are often in free form in the bloodstream, changes in the levels of carrier proteins would affect other hormone systems and could indirectly influence the overall endocrine physiology.