 Have you ever seen this picture before? Full circle, dog pounds, full circle. We're back to the thyroid gland, and there's someone that I didn't tell you about before. Yes, we have follicle cells making thyroid hormone, whatever. In your thyroid gland, you also have little guys called C cells, C cells. And they're found outside of the follicle. So if we looked in our little slide, we could look around and we could find follicle cells, and then we could find these bigger, like blobbier looking, less organized cells. Those are your C cells. C cells produce calcitonin. So let's take a second to go, dude, what does calcitonin do? Produces calcitonin, calcitonin. And calcitonin is the only one that's going to act to decrease. I'm just going to use this one. It decreases calcium concentration in the blood. So how is it going to decrease calcium concentration in the blood? It has one job. It puts the stop sign up to the osteoclasts. It says osteoclasts, you guys are crazy. Settle down. If the osteoclasts are not breaking up your bone, they're not going to put calcium into your blood. That's going to decrease calcium concentrations. Again, necessary only to must maintain calcium homeostasis in a really narrow range. Oh my gosh, it is a good night. Good night. I'll miss you while I'm gone, but not so much that I'm not happy that this lecture is done.