Patients treated for male pattern hair with finasteride show, after discontinuation of the drug, altered levels of neuroactive steroids in cerebrospinal fluid and plasma

Extending the 2013 CSF findings, the Milan group profiled neuroactive steroids by LC-MS/MS in paired plasma and CSF from post-finasteride patients versus healthy controls. In CSF, progesterone and its 5α-reduced metabolites dihydroprogesterone and tetrahydroprogesterone were reduced while the precursor pregnenolone rose; dihydrotestosterone fell as testosterone and 3α-diol rose. Plasma showed the same directional pattern: higher pregnenolone, testosterone, 3α-diol, 3β-diol and 17β-estradiol with lower dihydroprogesterone and tetrahydroprogesterone. The pattern reads as a persistent 5α-reductase-blockade signature — precursor buildup upstream, downstream metabolite depletion — still present after the drug was stopped. A 2023 corrigendum (DOI 10.1016/j.jsbmb.2023.106405) is attached to the record.

A larger follow-up confirmed and extended the 2013 findings: finasteride's effects ripple across the whole steroid-making pathway, not just the single step it blocks. Precursors pile up while downstream calming neurosteroids stay depleted — evidence of a broad, lasting rewiring of brain steroid chemistry.