This permanently damages the compounds structure, destroying its biological activity
However, oral bioavailability is much lower than injectable, meaning the doses are higher (3 mg, 7 mg, and 14 mg tablets compared to the 0.25 to 2.4 mg injectable range)
Experimental studies in animals provide additional insight: GLP-1 analogs increased testosterone synthesis and improved sperm mitochondrial integrity in diabetic and obese models
Russell AL, Kennedy AM, Spuches AM, Gibson WS, Venugopal D, Klapper D, Srouji AH, Bhonsle JB, Hicks RP (2011) Determining the effect of the incorporation of unnatural amino acids into antimicrobial peptides on the interactions with zwitterionic and anionic membrane model systems
Studies suggest the prevalence of deficiency in the UK is one in 10 people aged 75 and over, one in 20 aged 65-74, and lower in younger age groups except for vegans, where prevalence is around 11%