The DHT-Hair Loss Connection
Androgenetic alopecia (male and female pattern hair loss) affects the majority of men by age 50 and a significant proportion of women — and it’s one of the most common concerns practitioners encounter in hormone and men’s health practices. Understanding the biochemical cascade from testosterone to DHT, and the clinical tools to interrupt it, is essential for any practitioner in this space.
DHT Biochemistry
Dihydrotestosterone (DHT) is produced from testosterone via the enzyme 5-alpha reductase (5AR), which exists in two isoforms: Type 1 (skin, liver, brain) and Type 2 (prostate, scalp hair follicles, genital skin). DHT binds to androgen receptors in hair follicles with 3–5x the affinity of testosterone, causing follicular miniaturization — the progressive shrinkage of hair follicles that leads to pattern baldness.
5-Alpha Reductase Inhibitors
Finasteride (1mg for hair loss, 5mg for BPH) inhibits Type 2 5AR specifically, reducing DHT by approximately 70%. Dutasteride inhibits both Type 1 and Type 2, reducing DHT by 90%+ and is more effective for hair retention. Both are FDA-approved for male pattern baldness (finasteride) and BPH (dutasteride). They require 6–12 months of consistent use before meaningful hair density response is seen.
Post-Finasteride Syndrome: Acknowledging the Controversy
A subset of patients — estimated at 1–3% — report persistent sexual, neurological, and psychological side effects after stopping finasteride, a cluster known as Post-Finasteride Syndrome (PFS). While the mechanism remains incompletely understood and some researchers question its existence as a distinct syndrome, practitioners should not dismiss these reports. Thorough informed consent addressing sexual side effects (which occur in 2–4% of users during treatment), mood effects, and the potential for persistent symptoms is ethically and medico-legally required.
Finasteride on TRT
The interaction between finasteride and TRT requires careful clinical thinking. TRT raises testosterone, which increases substrate availability for DHT conversion. Some practitioners add finasteride to TRT protocols specifically to mitigate hair loss and reduce DHT-related prostate stimulation. Others avoid it due to the side effect profile. This is a nuanced, individualized decision requiring patient discussion.
Other Hair Loss Interventions
Minoxidil (topical or oral) remains a cornerstone treatment that works through a separate mechanism (vasodilation, potassium channel opening) and complements 5AR inhibition. Low-level laser therapy (LLLT), PRP (platelet-rich plasma), and microneedling with minoxidil have growing evidence. Nutritional deficiencies — particularly iron, biotin, zinc, and vitamin D — should be corrected before attributing hair loss to androgenetics alone.