The hormones I am reviewing here are derived from animal sources (usually sheep, cattle or goats), not human hormones. The hormones that are in a variety of products are usually found in animal source hormones, but can also be found in human source hormones. I know that many of the products contain animal source hormones, so I will not discuss any of them. However, I will mention that it is possible that the hormones are human derived in some products. I have seen some products that are marketed as "female hormones" or "female hormones-only." The product in this section of my site (here called "Female Hormones") is not labeled as a female hormone. Some of the most common hormones that are made in the animal kingdom are estrogen, progesterone, and testosterone. These hormones work by changing the levels of a group of proteins called androgens. Most of the androgens found in animals are produced in the testes of males. In fact, in one animal study, male rats were injected with either testosterone (testosterone) or estrogen (estrogen). In other words, the testes are the source of testosterone. However, in females, the testes don't produce testosterone. In a few animals, this makes the testes produce the estrogen. This estrogen in turn works by making the testes of females produce more testosterone. However, this can be dangerous in a male.