In addition, oral therapy has been found to have a positive impact in these patients on quality of life factors such as sexual function, mood, and mental status, as documented in various studies.

[11] The Reandron 1000 formulation (Aveed in the United States) contains 1,000 mg of testosterone undecanoate suspended in 4 ml castor oil with benzyl benzoate for solubilization and as a preservative, and is administered by intramuscular injection.

As an excipient in Reandron 1000, benzyl benzoate has been reported as a cause of anaphylaxis (a serious life-threatening allergic reaction) in a case in Australia.

[25] Bayer includes this report in information for health professionals and recommends that physicians "should be aware of the potential for serious allergic reactions" to preparations of this type.

Testosterone undecanoate has a very long elimination half-life and mean residence time when given as a depot intramuscular injection.

[46][47] Intramuscular testosterone undecanoate has been approved worldwide,[46][11] including the European Union, Russia, and the United States.

These men have low testosterone levels due to specific medical conditions, such as genetic disorders like Klinefelter syndrome or tumors that have damaged the pituitary gland.

[5] In July 2022, Kyzatrex, an oral testosterone undecanoate capsule, was approved for medical use in the United States.

[52][53] In 2013, a phase II clinical trial testing intramuscular testosterone undecanoate for the treatment of non-alcoholic steatohepatitis (NASH) was initiated in the United Kingdom.

[54] In the United States in 2018, Lipocine Inc. began investigating the potential of using an oral testosterone undecanoate formulation, known as LPCN-1144, in patients with NASH.

They study found that administering low-dose testosterone undecanoate (TU) at a rate of 20 mg per day to elderly men with low serum testosterone and osteoporosis effectively increases bone mineral density in the lumbar spine and femoral neck, and improves bone turnover, similar to the standard-dose TU (40 mg, per day) treatment.

Additionally, testosterone undecanoate therapy was found to lower fasting blood glucose and HbA1c levels and improve lipid profiles in this population.

One study concluded that long-term testosterone replacement therapy (TRT) in middle-aged men with late-onset hypogonadism (LOH) and metabolic syndrome (MS) led to a significant increase in both vertebral and femoral bone mineral density (BMD) after 36 months of treatment, as measured by dual-energy x-ray absorptiometry.

The TRT treatment was shown to induce a 5% per year increase in BMD without changes in body mass index (BMI).

The study suggests that long-term TRT could be beneficial for improving bone health in middle-aged men with LOH and MS, even in the absence of osteoporosis.