Ironically, testosterone replacement can increase a man’s estrogen levels (among other things) as the body breaks down testosterone into estrogen. This is useful, because even though we consider estrogen to be a female hormone, males also need it, albeit in much smaller concentrations than women.
One of the main enzymes that convert testosterone into estrogen is aromatase, which is found in higher concentrations in fatty tissue. This means that men who are overweight typically make more estrogen from testosterone and are more likely to have abnormal elevations of estrogen.
If estrogen levels are not monitored and remain elevated, they can cause significant side effects, such as breast enlargement, which can sometimes be irreversible.
Elevated estrogen levels also counteract several of the beneficial effects of taking testosterone, so when estrogen levels become elevated the TRT (Testosterone Replacement Therapy) benefits, particularly some of the sexual benefits, diminish or stop altogether. Elevated estrogen levels can also cause emotional irritability and increased “weepiness.”
When regularly monitored, elevated estrogen levels can be addressed early and the side effects avoided.