Long-term safety of HRT

Introduction
HRT and being trans appears safer for trans men than trans women. Trans men had similar mortality rates to the general population, with no added risk of cancer, cardiovascular events or osteoporosis. For trans women, total mortality was 51% higher than in population, though the same the study concluded that most of these adverse effects were "mainly due to non-hormone-related causes" (suicide, AIDS, and drug abuse), with the notable exception of cardiovascular disease, which was directly associated with ethinylestradiol use. Trans women aren't at a higher risk of cancer, but do suffer from osteoporosis, alarming rates of cardiovascular problems and lifestyle risk factors.

Most medical articles report risks only for "MTFs" and "FTMs," so little is reported medically about non-binary transgender health. Hopefully this is still useful to y'all.

Cardiovascular Health
Trans men are at no higher risk of embolism, thrombosis or other cardiovascular events than the general male population. In the study above, 6% of trans women experienced embolism and another 6% suffered other cardiovascular problems after ~11 years on HRT on average. The increased cardiovascular risk was associated only with current use of Ethinylestradiol (an older synthetic estrogen and still a common birth control medication), which was an independent, three-fold risk of cardiovascular death. (Do not use birth control to transition!! It may kill you.)

Ovarian Cancer

 * The incidence of ovarian cancer in transgender men is not known. There are roughly five cases reported medically. It seems very rare, but may be underreported.

Breast Cancer

 * In a study of 5,135 transgender veterans from 1996-2013, breast cancer in MTF or FTM patients receiving HRT did not occur at a greater rate than the general population.

Testicular Cancer

 * One trans women taking HRT developed a form of testicular cancer which tested positive for expression of the estrogen receptor. Since many trans women in the long-term studies above had orchidectomy or GRS, it's hard to estimate how likely testicular cancer is in long-term HRT users.

Other Cancers
In trans women, total mortality from cancer was not significantly different from the general population, but lung cancer (likely due to increased rates of smoking) and leukemia were significantly more frequent. The increased cancer risk is likely associated with Total mortality and types of cancer in trans men were roughly equivalent to the general population.