Describe the suspected effects of hormones being added to our foods. Is there a link between early puberty and the added hormones?

Added hormones, to varying extent, are used (or have been used) extensively in food production.  Hormones have been used in animals in order to make them grow faster, which increases profitability (the faster the animals grow large the faster they can be butchered.)  In addition, hormones have been used in milk production to increase the output of the cows.  The question you are asking is whether these added hormones have an effect on our health, specifically whether the added hormones are having an effect on the age at which puberty starts.  Let's take a look:

It is important to remember that whether or not "extra" hormones are added to animals, there are already hormones in them (in the same way that people have hormones in their blood.)  What the debate is concerned with is the addition of extra hormones.  The biggest concern people have with hormones being added to animals (cattle or cow,) aside from the distasteful nature of messing with nature, is that the hormones will cause an increase in the risk of cancer for those people who consume them.

There are six different kids of hormones that are approved for use in cattle and sheep, and one hormone that is approved for use in dairy cows.  The problem is that not a lot of good research has been done about the effect of these hormones on humans (when it comes to causing cancer or early puberty.)  Partially the problem is that the hormones are already naturally occurring within the animals in quantities that vary between animals...therefore, it becomes difficult to determine (looking at the milk or meat) how much of the hormone found there is natural and how much of it was a result of the application of the hormone artificially.

There are links between steroid hormones and breast cancer, as well as early puberty and breast cancer, but the amount of steroid hormone that might be transmitted by beef is tiny compared to the amount the body is naturally producing.  According to Cornell University: "The breast cancer risk of women who eat meat from hormone-treated animals has not been compared with the risk of women who eat meat from untreated animals." This further complicates things.

The situation is similar to the hormones introduced to dairy cows to increase milk production.  Though largely eliminated in the US due to public pressure (and banned in a lot of other places in the world) "growth hormones" in dairy cows "is effective in promoting growth in cows, but does not work in humans. Scientists know that rbGH is not recognized as a hormone by human cells." It would seem that the cow hormone does not have an influence on human beings, but that "evidence does not exist to answer this question. Use of rbGH for dairy cattle has been in practice in US for only six to seven years. Breast cancer can take many years to develop. It is too early to study the breast cancer risk of women who drink milk and eat milk products from hormone-treated animals."

So there you have it. People worry about hormones being added to their food and causing cancer or early puberty, but there aren't any good studies proving these theories.   That doesn't mean the links don't exist, but they have not been proven so far.  The opinion of a lot of people, though, is "why take the chance?"