“This is a great big fat ‘Oh, no,’” Anawalt said in reaction to Hegseth’s announcement. “We’re turning the clock back on rational healthcare. … I’m worried about the ethics. I’m worried about the health consequences. I’m worried about unnecessary evaluations, incorrect assessments, and incorrect diagnoses that lead to inappropriate prescriptions of testosterone.”

To understand why, let’s start with the basic question: Why might someone have low testosterone?

Causes of “low T”

Disease states that can cause low testosterone include genetic conditions, such as Klinefelter syndrome (when a male has an extra X chromosome) or a problem with the brain’s pituitary gland, which controls hormone levels in the body. Pituitary problems may come from damage, dysfunction, or tumors (which are often noncancerous).

For these patients, “It’s not difficult to make the diagnosis,” Anawalt said. Genetic tests can detect Klinefelter disease, for instance, confirming an explanation for low testosterone levels. Similarly, in patients with pituitary problems, tests for other blood hormones (such as luteinizing hormone and follicle-stimulating hormone) can confirm the source of the problem.

But these conditions are uncommon, affecting maybe 1 percent of men at most, Anawalt said.

Meanwhile, many other things can lower testosterone levels, such as: cancer treatments, medications (such as corticosteroids or opioids), anabolic steroids, obesity, HIV, surgery, trauma, stress, sleep deprivation, and the natural process of aging. Many of these causes would not necessitate testosterone replacement therapy. For someone with sleep deprivation, the best treatment would be rest, for instance.

Symptoms

In patients with true hypogonadism, the primary symptoms are lower libido, erectile dysfunction, lowered sperm count, breast enlargement or tenderness, reduced energy, reduced muscle mass, shrinkage of testes, mood changes (such as irritability or depressed mood), and hot flashes. Over time, low testosterone can cause loss of body hair, muscle bulk, and bone density, and it can reduce red blood cell counts.