The marketing of low serum testosterone (low T) as a common medical condition helped propel sales of testosterone gels, patches, injections, and tablets to about $2 billion in the United States last year, according to IMS Health, a health-care information company. A recent study published in the Medical Journal of Australia noted that the low-T trend is global. From 2000 to 2011, there was a “major and progressive increase” in testosterone use in 37 countries.