You often hear about someone being HYPOTHYROID or HYPERTHYROID.
This picture shows , at a glance , what all this HYP is all about :-)
We know that the Thyroid gland controls the body's metabolism processes at the cellular level. Its like the thyroid maintains a stable "rpm's (revolutions per minute)" for our body, keeping all our various bodily systems in a wonderful dynamic balance. When this balance is disturbed, either your metabolism can slow down, and sometimes it may also speed up. In the former case, one is supposed to have become HYPOTHYROID, and in the latter case HYPERTHYROID.
Since so many bodily functions are dependent on this metabolism, these HYPO and HYPER states, readily translate into symptoms you and I can observe, and which can show up in any system/part of your body.