Inositol

Inositol (usually myo-inositol) is a nutrient that helps build phosphatidylinositol/phosphoinositides (PI/PIP/PIP2)—key molecules used in intracellular “second-messenger” signaling. That matters for serotonin because 5-HT2 receptors (5-HT2A/2C/2B) signal through Gq → phospholipase C (PLC), which splits PIP2 into IP3 (inositol-1,4,5-trisphosphate) and DAG; IP3 then drives intracellular calcium signaling. NCBI In other words, “inositol signaling” is part of the core downstream machinery of 5-HT2 activation, and lab work has shown myo-inositol can modulate 5-HT2-mediated neuronal effects (including NMDA facilitation and certain desensitization phenomena) in vitro. PubMed

In the PFS/PSSD/PAS context, inositol isn’t typically discussed as an anti-androgen; the reason it comes up is that it may influence serotonin-linked signaling pathways (especially 5-HT2/PI-cycle pathways), and some people in these communities report that serotonin-active supplements can be destabilizing—causing a “flare” or “crash”—while others report benefit. inositol interacts with a serotonin-related signaling pathway that may be sensitive in some individuals, so reactions can be unpredictable.

Crash Anecdotes:

https://www.reddit.com/r/PSSD/comments/qqtows/be_careful_with_inositol/

https://www.reddit.com/r/PSSD/comments/rffm68/people_who_take_inositol_be_careful/

My Personal Risk Ranking:

High Risk of Permanent Worsening (for PFS/PSSD/PAS):
If you currently have PFS/PSSD/PAS, this substance may carry a high risk of worsening symptoms—potentially in a lasting way—and is best avoided.

Given the uncertainty and the potential severity of outcomes, the risk may not be worth the advertised benefits.