I predicted testoserone would lead to an elevated risk of cardiovascular events based on animal data and a recent tesosterone study that was terminated due to apparent adverse effects (ref. 1, TOM study). An older interventional study also hinted at harmful effects of testosterone (2). There was some reason to think that testosterone could explain the increased mortality of males (H. Sapiens and in some other species, see  for a discussion).
The new studies presented this later week at the ACC cast some doubt on those previous concerns. In the first study, Dr Zuber Ali (Aurora Health Care, Milwaukee, WI) and colleagues studied 7245 men, mean age 54 years, prescribed testosterone-replacement therapy for low testosterone (<300 ng/dL). The mean follow-up period was 1.78 years. Cardiovascular risk factors were documented in many patients, with 41% having dyslipidemia and 34% having hypertension. In the multivariate analysis, there was no increased risk of acute MI, stroke, or death at 3 years among the testosterone-treated patients compared with the untreated patients.
The short follow-up is worrying, but apparently a recent meta-analysi did not find any risk either. The last time I checked another study, the "T trial", with n=800 participants was still ongoing. We will see what this one shows.
Testosterone may be safer in the short-term to mid-term than we thought, but this does not rule out harmful effects in the long term (c.f. ref. 3).
1. Basaria S, Coviello AD, Travison TG, et al. Adverse events associated with testosterone administration. N Engl J Med 2010; DOI:10.1056/NEJMoa1000485.
2. HAMILTON J.B, & MESTLER G.E. (1969) Mortality and survival: A comparison of eunuchs with intact men and women in a mentally retarded population. J. Gerontol. 24:395
EDIT: Data added, TOM study corrected