Thyroid function tests are a series of blood tests used to measure how well your thyroid gland is working. Available tests include the T3, T3RU, T4, and TSH. The thyroid is a small gland located in the lower-front part of your neck.
Clipping path is a path or shape drawn from the shape tool as a rectangle or circle or any shape using pen tool. It is mainly used for clipping other layer over it. Means when you are having a image of a person standing and you made a shape of it and clipped it and see that the head shape is not proper, you can edit the shape afterwards.
http://cid-1ea90f0a909b94e1.skydrive.live.com/self.aspx/design tests/clipping path and crop marks and export/clipping path.png. I posted here an example I just draw a quick path I also added crop marks to let you see. you have to use export to save it.