When transgender men start gender-affirming hormone therapy (GAHT), one of the big questions is what happens to their bones and muscles over time. A new analysis pulled together the best available studies to look for patterns. The main finding is reassuring: after about four years of treatment, there was no significant change in bone mineral density at the hip or spine—areas that are clinically important for fracture risk. That suggests the therapy doesn't harm bone health at these key sites.
At the same time, the analysis found that GAHT was linked to positive changes in body composition and strength. Men gained lean body mass and their muscle strength increased. These are considered anabolic effects—meaning the treatment helps build tissue. The increase in muscle strength was particularly notable in the data.
However, it's crucial to understand the limits of this evidence. The researchers note that the studies they analyzed were methodologically weak and varied widely in how they were done. For some outcomes, like muscle strength and hip bone density, the results from different studies didn't align well, which makes the combined estimates less reliable. The analysis also didn't report on safety events or side effects.
What this means is that while these findings are encouraging, they come from a research field that still needs more robust, consistent studies. The takeaway isn't that all concerns are settled, but that the current best evidence points toward stability in bone density alongside gains in muscle mass and strength over several years of treatment. Doctors will still recommend monitoring bone health as part of routine care.
