Our hypothesis is that by using such and such method we can detect such and such substance in such and such part of the anatomy. This type of simplistic restatement of work is not a hypothesis in the scientific sense of the word. The point of your research proposal should be to develop experiments designed to test your hypothesis. The question often arises as to how many hypotheses are appropriate. One strong hypothesis is fine.
Some investigators have a hypothesis underlying each aim.
That is also fine. The question of how many hypotheses to include should be driven by the nature of the questions you seek to answer. The overall goal should provide the reviewer with a sense of not only what you wish to accomplish in the proposed research, but how this piece fits into your future plans. It is particularly important for a young scientist to provide the reviewer with a sense of future direction in this statement. This is because when the NIH commits to funding the proposal of a young scientist, they are also investing in that person's career.