Testosterone deficiency is diagnosed by a serum total testosterone level below 300 ng/dL in combination with symptoms such as decreased energy and libido. These symptoms can be ameliorated by restoring serum testosterone to the physiologic range with testosterone therapy (TT). There are numerous forms of testosterone therapy, such as injectable, transdermal, nasal, and subcutaneous applications. There are also multiple formulations of injection, such as testosterone cypionate, testosterone enanthate, and testosterone undecanoate. Testosterone undecanoate (TU) is a long-acting ester formulation of testosterone that can be provided in an injectable or oral form. Oral testosterone undecanoate is marketed as Andriol, Jatenzo, Tlando, and Kyzatrex. Oral TU provides a convenient option for many patients, which may increase compliance with TT. Injectable testosterone undecanoate is marketed as Aveed and Nebido. Injectable TT remains the most cost-effective therapeutic option and is appropriate for most patients as an initial therapy. This review describes the pharmacokinetics of these testosterone undecanoate products and provides a guide for prescribers using these medications. While many forms of testosterone are appropriate for TT, a patient-centered discussion focused on goals of care should best guide physician prescription of these medications.
Disorders of sperm production can be classified quantitatively as oligospermia (low sperm count) or azoospermia (no sperm during ejaculation). Numerous genes have been implicated in spermatogenesis. We describe a case of two identical twins who presented with different reproductive capabilities. One brother was infertile due to azoospermia, and the other, although oligospermic, previously naturally fathered a child. They were found to have differential gene expression based on RNA sequencing analysis. In the man with azoospermia, we found elevated E2F1 and HOXB9 gene expressions when compared with his brother, suggesting that the increased RNA expression of these genes could influence sperm production.
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