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Dax Shepard credits the size of his biceps to testosterone injections. Are they safe?

Experts expressed some concern about using testosterone injections to gain muscle.
/ Source: TODAY

Dax Shepard opened up about his use of testosterone injections in a new episode of his podcast, "Armchair Expert."

Shepard revealed that he was using the shots after guest Ashton Kutcher complimented him on the size of his biceps. Kutcher said that Shepard looked "phenomenal," comparing him to Joe Rogan and the cartoon character He-Man.

"I spent my whole life as a medium boy, and now I'm a big boy and I like it," Shepard said, explaining that he was working out six days a week, using heavy weights and taking "heavy testosterone injections."

When Kutcher and his wife, Mila Kunis, expressed concern about Shepard's use of the injections, Shepard said that he was also using them due to a family history of low testosterone.

What are testosterone injections?

According to Dr. Aren Skolnick, an endocrinologist with Northwell Health based in New York, testosterone injections are just one form of testosterone supplements that can be given; the hormone can also be administered with oral medications or topical treatments. Testosterone injections are administered by a doctor every few weeks, depending on which formulation a patient is taking.

"The physician will inject the testosterone and usually you'll see an increase in testosterone levels within a couple of days, with a peak level in about a week or so, depending on the formulation. Then depending on which type of testosterone it is, that level could last anywhere from a week up to maybe three weeks," said Skolnick, who noted that injections tend to be "one of the more common" methods of administering testosterone.

Dr. Karl Nadolsky, a clinical endocrinologist at Spectrum Health in Grand Rapids, Michigan, said that these treatments are approved for "what we call pathological clinical conditions of hypogonadism" or side effects of not having enough testosterone. Men can have a variety of conditions that lead to not producing enough testosterone, including tumors, family history or genetic disorders. Testosterone injections are also approved for use in gender-affirming care.

Skolnick said that men with a history of substance use may also have low levels of testosterone. Shepard has been candid about his addiction struggles, recently sharing that he had relapsed in September 2020.

"I personally always ask, when someone comes in with low testosterone, about opioid use or methadone or Suboxone use, all of which have the mechanism of decreasing pituitary function ... to stop testosterone production," said Skolnick.

Both Skolnick and Nadolsky said that they would be concerned about a patient using testosterone injections solely for workout purposes.

"Obviously (testosterone injections) have become more famous for people recreationally using them as anabolic androgenic steroids," Nadolsky said. "They unfortunately have become sort of a moneymaker for men's heath clinics and such, because you'll see signs like 'Are you not feeling well? Come get your (testosterone replacement therapy).' In some cases, they're being sold and marketed to people that don't actually have clinical pathologic hypogonadism."

Skolnick said that using testosterone injections solely for workout purposes is "not all that different" from using steroids.

"The anabolic steroid use regimens typically do involve the same testosterone that we give as a testosterone supplement in patients who are lacking testosterone," said Skolnick. "But then (steroid regimens) also use supplements on top of that, not to increase testosterone production but to increase anabolic function, and there's a whole list of different things that are anabolic agents that are used in conjunction with testosterone itself for anabolic steroid use."

What are the side effects of testosterone injections?

Skolnick said that there is little "long-term data" or "nice and robust data on men ... who are on testosterone for long periods of time." One major risk of using testosterone supplements is polycythemia, a condition where the body produces too many red blood cells which can lead to an increased risk of blood clots, stroke or heart attack since they can block veins and arteries.

Nadolsky said that there is some evidence that testosterone injections can exacerbate sleep apnea and increase cardiovascular risks. Taking unnecessary testosterone injections or supplements can also affect your natural production of testosterone, since the body parts that typically produce testosterone "don't need to work and kind of shut down," according to Nadolsky.

"Something that I see in some patients who come in with a history of anabolic steroid use, where they were trying to build muscle and taking very high doses of testosterone early in their (life), and that, in a sense, shut off their own production of testosterone," said Skolnick. "That could be permanent or it could be temporary but for prolonged periods of time."

Other side effects, like the growth of breast tissue, an increase in acne and mood swings are also possible.

Is it safe to use testosterone injections with a history of substance use?

Nehal Vadhan, an addiction specialist and assistant professor at the Feinstein Institutes for Medical Research in New York, said that he would be concerned about someone with a history of substance abuse using testosterone injections without an immediate medical need. While testosterone itself "doesn't really produce any kind of subjective intoxication or high that would closely resemble" drug use, there is some concern because of the delivery mechanism.

"Anything that resembles the paraphernalia that was used with the previous substance use disorder could be problematic and triggering," said Vadhan, noting that there would be less concern if the mechanisms were not the same; for example, if a person had a history using illicit drugs in pill form and was having testosterone injected.

While the body can become reliant on injected testosterone and stop naturally producing testosterone as a result, Vadhan said that testosterone does not "produce anything resembling intoxication or its rewarding effects."