Newer formulations of oral testosterone undecanoate: development and liver side effects.

Previous oral testosterone formulations, particularly methyltestosterone, have been associated with adverse liver effects, while newer oral TU formulations have a different mechanism avoiding first-pass hepatic metabolism.

• Methyltestosterone was associated with hepatotoxicity concerns that have limited adoption of newer oral testosterone products.
• Oral TU is absorbed via intestinal lymphatic transport, bypassing first-pass hepatic metabolism.
• The review clarifies the mechanism of action of oral TU to distinguish it from older formulations associated with liver toxicity.
• Prescribing physicians may still be concerned about adverse liver effects based on older methyltestosterone data.

Pooled safety data from individual studies of newer oral TU formulations showed no clinically significant liver toxicities in clinical trials.

• The authors pooled data from individual studies of oral TU products to present a safety summary.
• Increased liver function test values are 'not generally associated with oral TU formulations.'
• No clinically significant liver toxicities were noted across clinical trials of oral TU.
• The review presents a comprehensive assessment of relevant liver safety findings from the available literature.

Many different routes of testosterone delivery have been developed, each with their own administrative benefits and challenges.

• Routes of delivery reviewed include oral, injectable, transdermal, and other formulations.
• Oral TU provides 'a convenient administration option' among the available testosterone delivery methods.
• The history of oral testosterone development is discussed to contextualize current formulations.
• Use of oral TU has been limited by hepatotoxicity concerns despite the availability of newer safer formulations.

Testosterone deficiency is a clinical disorder resulting from failure of either the testes or the hypothalamic-pituitary axis.

• Testosterone deficiency arises from 'either failure of the testes to produce testosterone or failure of the hypothalamus or pituitary to produce sufficient gonadotropins.'
• The condition requires therapeutic intervention, with oral TU representing one treatment option.
• The review addresses both the clinical disorder and the historical context of its pharmacological management.

Continued research into the safety of oral TU is needed to better understand potential risks, and patient education and reassurance regarding oral TU safety are important.

• The authors highlight 'the importance of providing patient education and reassurance regarding oral TU safety.'
• Continued research will 'contribute to a better understanding of the potential risks in patients receiving this therapy.'
• The review aims to help physicians distinguish between hepatotoxicity risks of older formulations versus newer oral TU products.