Trego's Mountain Ear

Testosterone (which, for the sake of simplicity, we treat as if it’s a single thing and not a category word like ‘hawk’ or ‘cake’ with many subcategories) is a precursor molecule for estrogen (another category word, as it happens).

What does that mean? When students learn about chemical reactions, they are taught them as if they occur in a single step, react completely, and in only one direction. All of this is a vast oversimplification. The degree of oversimplification becomes even greater for organic chemistry, where the molecules involved are increasingly complex.

The short version: Making estrogen is a multi-step process, and testosterone is an important step along the way. All estrogens start out as testosterones.

The enzyme generally responsible for this conversion is aromatase. Interestingly, this is a biological pathway that pretty much runs in one direction. Testosterone convers into estrogen, but the reverse doesn’t occur.

What are the consequences? Among other things, this means that both men and women with low testosterone are also likely to show symptoms of low estrogen as well.

More interesting trivia, is that while artificially increasing testosterone levels can increase estrogen, it doesn’t necessarily always do so to a clinically significant amount. This implies there’s a mechanism at play determining the rate of conversion between testosterone and estrogen, but details on that don’t seem especially well studied. In general, the body will inhibit enzymes to downregulated their activity, so it’s probable that’s what going on in that instance.

Anyway- neat!