[b]Since this is forum is a free exchange of ideas I would like to post my own theory:
Dr Crisler, I would like you to read this theory on why people may experience the ‘crash’ and persistent side effects from finasteride. I would be interested to know if you think it is possible that any of what I say could actually be happening – I am very far from being an expert.
Although this theory fits my own personal experience best (I took Propecia, stopped and ‘crashed’ then developed unexpected yet serious and on-going mental, physical and sexual side effects) it may also help explain the reasons why some people develop problems that appear whilst taking the drug that simply never go away.
As far as I can understand, this theory is the ONLY theoretical condition that fits with my symptoms.
A. Finasteride may be metabolised differently depending on each individual and can actually inhibit its own metabolism [1].
B. If this occurs there may be higher serum levels and higher chances of side effects, such as erectile dysfunction and loss of libido, as seen when higher doses of 5aRIs are administered [2]. The reasons for these symptoms are the same as Prof Traish explained.
C. Finasteride inhibits its own metabolism in a unique manner [1]. It directly inhibits the Pregnane X Receptor (PXR) which controls the Phase 1 & 2 metabolism of both xenobiotics AND sex hormones.
Phase 1 metabolism via the hepatic CYP3A4 enzyme, where xenobiotics and sex hormones are hydroxilated (deactivated).
Phase 2 metabolism via the sulfotransferase enzyme where xenobiotics and sex hormones are deactivated and made water soluble for excretion. (this phase can occur by itself instead of Phase 1).
D. So why do some ‘crash’ and perhaps others not get better?
My theory is that when some people stop using finasteride there is now an over-expression of the PXR and therefore an increase in the Phase 1 & 2 metabolism of sex hormones (and possibly thyroid hormones too).
E. I believe that this is the mechanism behind the crash because experiments where the PXR has been over-expressed have actually been shown to be a way by which prostate cancer can be deprived of androgens, effectively deactivating the sex hormones in serum, creating a novel state of hypogonadism, all without inhibiting the production of testosterone. [3] (In other words: a state of androgen resistance despite the existence of normal levels of testosterone).
F. There are some good coincidences if this is true.
An over-active PXR will also lower Vitamin D levels [4], amongst other things.
Hydroxilated testosterone is an excellent substrate of 5aR [5] (possibly leading to cross-reactivity of metabolites.)
The reason for low 3aDiolG therefore could be that 3aDiol isn’t being conjugated with Glucurinide but with Sulphate.
[1] Inhibition of Human Steroid 5β-Reductase (AKR1D1) by Finasteride and Structure of the Enzyme-Inhibitor Complex jbc.org/content/284/30/19786.full
[2] Adverse Side Effects of 5α-Reductase Inhibitors Therapy: Persistent Diminished Libido and Erectile Dysfunction and Depression in a Subset of Patients ncbi.nlm.nih.gov/pubmed/21176115
[3] Pregnane X receptor as a therapeutic target to inhibit androgen activity ncbi.nlm.nih.gov/pubmed/2…?dopt=Abstract
[4] The Pregnane X Receptor: From Bench to Bedside ncbi.nlm.nih.gov/pmc/articles/PMC2535920
[5] Inhibition of steroid 5α-reductase and its effects on testosterone hydroxylation by rat liver microsomal cytochrome P-450 dx.doi.org/10.1016/0003-9861(8890386-4)
Thanks![/b]