“Gentlemen, restart your engines,” is fast becoming the motto of one of North Texas’ fastest growing businesses. And, it has nothing to do with racecars. Some would say it has to do with “the fountain of youth.” Mike Sisk is building a business empire on low testosterone. Sisk opened his first Low T Center in Southlake in 2010 and, as of early May, he had expanded to 25 centers specializing exclusively in the diagnosis and treatment of men with low testosterone. Number 26 is slated to open May 28 in Mansfield. In 2012, Low T Centers administered 106,782 testosterone injections to 5,888 men, at 19 locations, Sisk said. There are now 15 Low T Centers in Texas. The Fort Worth-Dallas area now has eight. Sisk has also opened centers in Houston, San Antonio, Oklahoma City, Kansas City, Denver, Indianapolis, Nashville, Cincinnati and Columbus, Ohio. Next, he has his sights on Chicago and New York. “The difference the treatment made in my life was so dramatic, yet the therapy was so simple, and it was covered by my health insurance. I thought, for any man that has low testosterone, this should be an absolute ‘no brainer,’” says Sisk, founder and president of Low T. “A lot of guys swear by the stuff,” said one 64-year-old man, who is not a Low T customer. “Testosterone runs your whole body – from bone density to muscle tone, and by the time you are 60, you are pretty much operating on 20 percent of what you had at 18. My doctor said your body just stops producing it. “Guys will do just about anything to get back their vitality,” said the man who owns and runs a construction company, but asked to remain anonymous. “I know men my age who say they use it mostly for energy so they can work out and get back in shape, but there’s a saying out there, that a man’s two biggest fears are getting old and not getting it up,” he said. He uses AndroGel, a rub-on testosterone gel, prescribed by his physician and covered by his health insurance, but said friends who take injections are even happier with their results. The best-known and most important male hormone, testosterone is most often associated with male sexual development and libido. Testosterone injections were once primarily considered a treatment for erectile dysfunction. But, diminished sex drive is far from the only symptom affected by testosterone deficiency. Studies over the last 20 years have underscored the importance of testosterone levels in diagnosing and treating fatigue, decreased strength and energy, lack of motivation, weight gain and increased irritability and depression. Some research has also associated low testosterone with cardiovascular disease, diabetes, metabolic syndrome and osteoporosis, according to a recent CME Expert Column, published online by Medscape. “Testosterone deficiency in men remains a topic of debate and controversy because of gaps and inconsistencies in our understanding of the condition. Yet, information linking TD to serious co-morbidities and increased mortality has been accumulating, and enough is known about TD to argue that it merits greater clinical attention and concern,” Dr. Martin Miner, wrote in the column. He is co-director of the Men’s Health Center and chief of family and community medicine at the Warren Alpert School of Medicine at Brown University. Off to a fast start this year, Low T Centers provided 15,700 testosterone injections in January and opened five new locations between mid January and Feb. 18. The success has come as no surprise to Sisk, who founded the company the same year his doctor diagnosed his own low testosterone, and he began injection therapy. Low T Centers all have MD or DO medical directors. They require patients to come into their offices to get testosterone injections every 10 days, and all patients are diagnosed and closely followed with blood tests. A normal testosterone level is between 350 and 1,000, according to Low T literature. About 80 percent of Low T’s patients are covered by health insurance. For patients without insurance, treatment runs $395 per month for office visits, exams, lab tests and three injections, according to the company website.