Older men who receive intramuscular testosterone injections may not be at higher risk for myocardial infarction (MI), according to a group of researchers from the University of Texas Medical Branch.
Their study, published online this month in The Annals of Pharmacotherapy also found that testosterone “modestly” protected men at the highest risk for MI.
In the United States, the number of testosterone prescriptions has increased threefold over the past ten years, the researchers said. Companies have marketed testosterone directly to patients, low testosterone clinics have opened, and new forms of testosterone delivery have been developed, all contributing to the rise in prescriptions.
In spite of this, research on testosterone in older men has had mixed results. Some studies have found that the hormone has a negative impact on heart health. Others have found the opposite.
For the present study, researchers examined the medical records of 6,355 male Medicare beneficiaries age 66 or over who had had at least one intramuscular injection of testosterone between January 1, 1997 and December 31, 2005. These records were compared to those of 19,065 similar men who did not undergo testosterone therapy.
After analyzing the data, the team found that testosterone therapy was not associated with higher MI risk. In addition, men in the highest MI risk quartile saw their risk decrease.
“The association between testosterone therapy and cardiovascular disease is complex,” wrote the study authors. Past research has suggested that testosterone therapy might decrease fat mass, insulin sensitivity, and lipid profiles. Testosterone may also have anti-inflammatory and anticoagulant properties. All of these factors can be beneficial for patients.
On the other hand, testosterone may raise the risk of cardiovascular disease because it increases salt and water retention. It may also raise the risk of coagulation and platelet aggregation, left ventricular hypertrophy, and systolic and diastolic dysfunction. These factors can have a negative impact on heart health.
The researchers noted that intramuscular testosterone could have different properties than other forms and this might have affected their results. They also did not know whether the participants were on medications that could have lowered their risk for MI.
Testosterone therapy needs further study, they said. “In view of the large increase in the use of testosterone therapy in recent years, examining the short- and long-term risks of testosterone therapy holds increasing clinical and public health relevance.”
The Annals of Pharmacotherapy
Baillargeon, Jacques, PhD, et al.
“Risk of Myocardial Infarction in Older Men Receiving Testosterone Therapy”
(Full-text. Published online before print: July 2, 2014)