A longevity researcher started taking testosterone in his 50s. He says there are 4 things everyone should know before considering TRT.

• Matt Kaeberlein, a longevity researcher and CEO of Optispan, had symptoms of low testosterone.
• He got his levels tested in his 50s and gradually began testosterone replacement therapy (TRT).
• He said everyone should know 4 things before starting TRT.

In 2020, longevity researcher Matt Kaeberlein started wondering if he had low testosterone levels.

Then, in his early 50s, Kaeberlein had all the classic symptoms: low energy, a substantial drop in libido, and an inability to change his body composition, even though he was consistently strength training and following a balanced diet.

"Even though you're working out hard, you're just not seeing loss of fat and increase in muscle," Kaeberlein, now 55, told Business Insider.

Kaeberlein saw a doctor and got his testosterone levels tested that year, but it took more testing — and some trial-and-error with medications and supplements — for him to figure out a treatment plan that works for him. Now the CEO of Optispan, a healthcare technology company focused on making proactive longevity and healthcare practices more accessible to the general public, he said working in that space helped him navigate the early days of his low testosterone diagnosis and treatment.

He said TRT can be stigmatized for a few reasons. On one hand, "there's this idea that being natural is just better, which I don't really subscribe to," he said. Based on his own research and experience, TRT can be almost as significant for middle-aged people as eating protein-rich whole foods or moving enough throughout the day, as testosterone starts declining for most people in their 30s, with more notable symptoms appearing around their 40s or 50s.

On the other hand, "it's also being massively abused these days," he said, with men in their 20s and 30s flocking to get testosterone boosters when they might not actually need them. It mirrors the heavy steroid use of the 70s through 90s, which can add to the stigma, Kaeberlein said.

To demystify the world of TRT, Kaeberlein shared what he learned from his own experience with supplementing testosterone.

You can have low testosterone and still show 'normal' levels

When he first suspected low testosterone, Kaeberlein saw his primary care physician.

He performed a common blood test called "total testosterone," which measures all of the body's testosterone levels, but doesn't account for which proteins are biologically active.

By itself, the test can be fairly meaningless, Kaeberlein said. His levels were "low-normal," or in the lower 50% of the reference range. His doctor said he was fine and didn't need hormone replacement therapy.

As Kaeberlein became more educated in the healthcare space, he learned about alternative testing options. A friend of his who was experiencing similar symptoms pointed Kaeberlein to an online company where consumers can order specialized bloodwork without seeing a doctor.

Kaeberlein ordered a "free testosterone" test, which measures more specific hormones connected to testosterone and sperm production, in addition to measuring his total testosterone. Companies like Labcorp and QuestDirect offer such panels.

His results indicated that he had "primary hypogonadism," a form of testicular failure that means his pituitary gland is sending the signal from his brain to make testosterone, but his testes aren't able to create it.

He sought out a new doctor who had more experience with testosterone therapy to figure out his treatment plan.

'Natural' supplements probably won't work

After he confirmed he had low testosterone, Kaeberlein had a dilemma: he didn't want to inject himself.

"I don't have a needle phobia, but it just didn't seem like something I really wanted to do," he said.

He looked for natural ways around it, such as taking supplements said to boost testosterone. They didn't work for him.

He then tried Jatenzo, an oral testosterone medication, which did make a difference, but also included some side effects, he said.

Eventually, his doctor encouraged him to just learn how to inject himself. Since then, Kaeberlein has been taking weekly testosterone injections and has had success with them.

"I took a long time to get to the point where I was comfortable with the idea of taking testosterone," he said. "I think there's still a little bit of a stigma. There shouldn't be."

Know where you stand on having kids

After injecting a synthetic testosterone hormone, the male pituitary gland receives the signal to stop producing hormones responsible for creating sperm.

This can lead to infertility, Kaeberlein said. While it's possible to stop TRT and slowly regain sperm production, it can take months or even a few years. In some rare cases, it never fully returns.

"In my case, it wasn't an issue," Kaeberlein said. "We were done having kids." But for younger men, the conversation around how TRT affects conception is sometimes overlooked.

TRT should be the missing piece to an already healthy lifestyle

After starting injections, Kaeberlein has felt "an amazing improvement" in his body composition as well as energy and libido levels.

He also made more drastic lifestyle changes around the time he started injecting, including cutting back on alcohol and becoming more regimented with his exercise routine. He believes TRT helped him reach the full benefits of these habits.

"I think a lot of people have this experience where you feel like you're working really hard and there's just one piece that you're missing in the puzzle," he said. It also underscores an important point: while testosterone, in some cases, can increase some lean muscle mass without strength training, it isn't a magic pill for looking and feeling stronger.

"If men are looking for increased muscle mass and strength, testosterone alone isn't going to do it," he said. "You really need to get dialed in on exercise and nutrition."