T4 is the main thyroid hormone. If your levels are dropping, then your thyroid gland is not producing enough hormone or something is interfering with the hormone's action somehow. In either case, your doctor will need to determine if you need to supplement your T4 with oral medication.

the head

it will raise t4 levels

The old Total T4 test (TT4) is no longer considered the best way to test for T4 levels. T4 and T3 can both be bound by other proteins and hormones in the body. When this happens, the T4 or T3 is not usable by the body. The body can only use T4 and T3 that is not bound, or free. For this reason, Free T4, which only tests the free levels of the hormone, is now preferred over Total T4 testing as more accurate.

T4's "full name" is "Enterobacteria phage T4"!