At the end of each strand of DNA is an "end cap" called a "telomere". The main feature of a telomere is that it contains a number of repetitions of a particular sequence of base-pairs. The process of cell-division involves, as you know, copying all the data from existing DNA strands to new DNA strands. However, the actual mechanism for doing that copying is imperfect, and can't QUITE copy all the duplicate stuff in the telomeres. This is OK, because that is what the telomers are FOR! They exist to be partially sacrificed during cell-division, so that all the critical genetic code BETWEEN the end-cap telomeres is completely copied.

Well, in single-celled creatures, after cell division occurs, a certain enzyme, known as "telomerase", is produced that causes certain cellular machinery to get into action, to add some new duplicate base-pairs to the ends of the telomeres, replacing the portion lost during cell-division. Thus the final result is a cell that is as identical as possible to the parent cell, before division occurred. It is practically impossible to declare that one particular cell, that resulted from the division, IS the parent cell, while the other cell is simply "offspring". BOTH are offspring, and yet both are equal to the parent cell. Single-celled creatures are considered to be immortal, as a consequence.

Now, it happens that in multicellular animals, telomerase generally is NOT produced after cell-division. Each animal starts out with an initial length of telomeres at the ends of its strands of DNA, and after some number of cell-divisions, that length shrinks to the point of worthlessness. A cell usually stops dividing, grows old, and dies. Eventually the whole multicellular animal dies too, of course -- including humans.

There are two main exceptions. First, in the reproductive organs, cells are "singled out" to produce telomerase, to rebuild their telomeres, and to then divide into 4 half-cells, which become the sperm and egg cells necessary for the next generation. (I may have the details slightly mixed up, but the general notion is correct.) At least one genetic disease ("progeria", I think its called) is associated with the failure of the parent reproductive cells to rebuild the telomeres. Human children suffering from that disease usually die by age 12, of old age -- and LOOK old, too.

The second exception is called "cancer". Cancerous cells grow and divide, alarmingly continuously, practically forever -- and they can do that because cancerous cells do indeed produce the telomerase needed to rebuild telomeres after cell-division.

Because of the association of telomerase with cancer, there is/was considerable concern whether or not cancer can be caused by introducing telomerase into an ordinary multicellular organism. The experiments that I've read about, however, so far indicate that various test-animals have successfully rebuilt telomeres, restarted cell division, and become more youthful, WITHOUT developing cancer. I'm sure lots of other experiments are going on, about which I've heard nothing, so I won't claim that the final verdict on the matter is in.

With most of the background information now presented, only a little remains. Telomerase is one of those delicate enzymes that cannot be put into a pill and swallowed -- the digestive system will destroy it before it enters the bloodstream. However, telomerase is a natural cellular product, and cells are, individually, purely stimulus/response mechanisms....

Simply BECAUSE the production of telomerase by a cell can be turned on and off, there MUST exist a trigger-signal (maybe two, but an OFF signal is only needed if the ON signal is not time-limited). I will refer to that trigger as "Telomerase Production Hormone", because hormones are a general category of substances that a multicellular animal normally uses to tell specific parts of its body to begin producing various proteins (such as enzymes) for various purposes.

Immediately there is a bit of a conundrum involved here, because in Nature telomerase is an INTERNAL enzyme. INSIDE a cell is where ALL the production-triggers are located, with respect to the normal workings of telomerase. Inside the cell something triggers something that triggers something ... that triggers production of telomerase, which in turn triggers the rebuilding of the telomeres.

Nevertheless, telomerase itself, when located OUTSIDE a cell, can enter the cell and immediately begin triggering the rebuilding of telomeres. This implies that among all those OTHER triggers, we should be able to find something (which we can CALL, even if it isn't really, "Telomerase Production Hormone") that can also enter the cell, and set the process in motion. Depending on just how many triggers there are in the chain, we may even be able to find something we can put in a pill.