Why estrogen, progesterone etc. in the contraceptive pills survive the acid environment of the stomach and all the digestive enzymes, while testosterone needs to be injected or spread with a gel on skin?
I have no idea of why this difference in assumption, because I know testosterone and "feminine" hormones have the same steroid based structure...so I can't pick up why testosterone differently from "feminine" hormones can't resist the digestion.

  • 2
    $\begingroup$ Testosterone can be administered orally as undecanoate ester (brand name Andriol). The big challenge of oral steroid hormones is not the acid degradation, but liver first pass metabolism. (Which is mitigated by adding alkyl group at the alpha-17 position, or use of fatty acid ester; see for instance ethinylestradiol, levonorgestrel, or estradiol valerate) $\endgroup$
    – Eliane B.
    Dec 23 '16 at 18:17
  • $\begingroup$ so why the testosterone pill is very rarely prescribed? It is proved that the female pill with the chemically modified hormones is effective. So why the testosterone pill is not considered enough effective in the oral form so that It is rarely prescribed. $\endgroup$ Dec 23 '16 at 23:33
  • $\begingroup$ Probably depends on where you live, it isn't rarely described here in the Netherlands, although transdermal gels are winning terrain. I think an argument from a pharmacological point of view would be the varying bioavailability of oral testosterone undecanoate. $\endgroup$
    – pbond
    Dec 24 '16 at 0:03

As stated in the comments by Eliane B., testosterone can actually be administered orally when an undecanoate ester is attached. The reason regular testosterone cannot be adminstered orally is because it undergoes extensive first pass metabolism (oxidation of the 17b-hydroxyl group to a 17-keto group, catalyzed by 17b-hydroxysteroid dehydrogenase enzymes, which are active in the liver). The undecanoate ester makes the substance lipophilic enough to be transported by the lymphatic system to the circulation after absorption by the intestines. Without the ester it will first reach the liver via the portal vein, thus exposing it to first pass metabolism. Nevertheless, bioavailability of oral testosterone undecanoate is estimated to be less than 10% [1].

Besides that, there are also derivates of testosterone which have a high oral bioavailability. These derivates have an alpha-oriented alkyl group, usually methyl, at position C-17, which retards hepatic metabolism. However, this can lead to hepatotoxicity [2].

  1. https://www.ncbi.nlm.nih.gov/pubmed/3770015 (note, the subjects were women, but in the literature it is assumed that similiar bioavailability is obtained in men)
  2. https://www.ncbi.nlm.nih.gov/pubmed/27372877

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