Daily research notes from Regrowth Index: short, citation-friendly answers to specific hair-loss questions, each linking out to the full guide.https://regrowthindex.com/en-ushttps://regrowthindex.com/notes/spironolactone/https://regrowthindex.com/notes/spironolactone/Spironolactone is a common second-line treatment for female pattern hair loss. Anti-androgen, oral, prescribed off-label. Not for men. Not safe in pregnancy.Wed, 20 May 2026 00:00:00 GMTFPHLHelena Marshhttps://regrowthindex.com/notes/fin-vs-te/https://regrowthindex.com/notes/fin-vs-te/Finasteride does not help telogen effluvium. Different mechanism. TE is a synchronised shed after a trigger, not DHT damage. Finasteride only works on DHT-driven loss.Tue, 19 May 2026 00:00:00 GMTMechanismHelena Marshhttps://regrowthindex.com/notes/dht/https://regrowthindex.com/notes/dht/Pattern hair loss is driven by DHT (dihydrotestosterone) shrinking susceptible follicles over years. Finasteride and dutasteride work by blocking the enzyme that makes it.Mon, 18 May 2026 00:00:00 GMTMechanismJames Ardellhttps://regrowthindex.com/notes/oral-minox/https://regrowthindex.com/notes/oral-minox/Low-dose oral minoxidil (0.25 to 5 mg/day) is the quiet revolution in hair loss treatment. As effective as topical for many people, easier to take, fewer scalp side effects.Sun, 17 May 2026 00:00:00 GMTOral minoxidilJames Ardellhttps://regrowthindex.com/notes/prp/https://regrowthindex.com/notes/prp/PRP for hair loss has real but modest effects in androgenetic alopecia. Three monthly sessions, then maintenance. Not a substitute for finasteride or minoxidil.Sat, 16 May 2026 00:00:00 GMTPRPJames Ardellhttps://regrowthindex.com/notes/microneedling/https://regrowthindex.com/notes/microneedling/Microneedling adds a real bump to topical minoxidil for AGA. The data is consistent. The catch: weekly sessions, 1.5mm depth, for at least 12 weeks.Fri, 15 May 2026 00:00:00 GMTMicroneedlingJames Ardellhttps://regrowthindex.com/notes/recap/https://regrowthindex.com/notes/recap/What we cover at Regrowth Index: every form of hair loss, the diagnostic flow, the bloods worth requesting, what each treatment actually does. Every claim cited.Thu, 14 May 2026 00:00:00 GMTAboutHelena Marshhttps://regrowthindex.com/notes/when-derm/https://regrowthindex.com/notes/when-derm/See a dermatologist sooner if there's redness, scaling, itching, burning, pain, or visible scarring. Those suggest a different category.Wed, 13 May 2026 00:00:00 GMTUrgentHelena Marshhttps://regrowthindex.com/notes/tracking/https://regrowthindex.com/notes/tracking/Photographs of the same scalp area, under the same lighting, taken a month apart. Beats counting shed hairs in the drain.Tue, 12 May 2026 00:00:00 GMTTrackingHelena Marshhttps://regrowthindex.com/notes/transplant-reality/https://regrowthindex.com/notes/transplant-reality/A hair transplant doesn't grow new hair. It moves existing follicles. Realistic density is 30–50 units/cm². Original full hair is 60–100.Mon, 11 May 2026 00:00:00 GMTHair transplantsJames Ardellhttps://regrowthindex.com/notes/finasteride-stats/https://regrowthindex.com/notes/finasteride-stats/In 5-year data, finasteride 1mg/day stabilised or improved hair in ~90% of men with AGA. The placebo arm continued progressive loss.Sun, 10 May 2026 00:00:00 GMTTreatmentJames Ardellhttps://regrowthindex.com/notes/ferritin/https://regrowthindex.com/notes/ferritin/Ferritin is the single most useful blood test for hair loss. Hair specialists target above 50 ng/mL; some target 70.Sat, 09 May 2026 00:00:00 GMTBloodsHelena Marshhttps://regrowthindex.com/notes/biotin-myth/https://regrowthindex.com/notes/biotin-myth/Biotin only helps with hair if you're actually deficient, which is rare. No supplement has been shown to shorten telogen effluvium in well-nourished people.Fri, 08 May 2026 00:00:00 GMTEvidenceHelena Marshhttps://regrowthindex.com/notes/diagnostic-shortcut/https://regrowthindex.com/notes/diagnostic-shortcut/Three observations narrow most hair-loss diagnoses: pattern, speed, scalp condition. The combination usually points to one cause.Thu, 07 May 2026 00:00:00 GMTDiagnosisHelena Marshhttps://regrowthindex.com/notes/alopecia-areata/https://regrowthindex.com/notes/alopecia-areata/Alopecia areata is autoimmune disease, not a cosmetic problem. ~50% of patchy AA spontaneously regrows within 12 months.Wed, 06 May 2026 00:00:00 GMTAlopecia areataHelena Marshhttps://regrowthindex.com/notes/pattern-vs-te/https://regrowthindex.com/notes/pattern-vs-te/Pattern hair loss is gradual over years, in specific zones, with progressively thinner shed hairs. Telogen effluvium is sudden, diffuse, full-thickness shedding 2–4 months after a trigger.Tue, 05 May 2026 00:00:00 GMTDiagnosisHelena Marshhttps://regrowthindex.com/notes/covid-shed/https://regrowthindex.com/notes/covid-shed/Post-COVID hair loss is real and almost never permanent. The trigger has already happened. What's needed now is patience.Mon, 04 May 2026 00:00:00 GMTTelogen effluviumHelena Marshhttps://regrowthindex.com/notes/postpartum/https://regrowthindex.com/notes/postpartum/Postpartum hair loss is common, alarming, and almost always temporary. Peaks around month 3–4. Resolves by 9–12.Sun, 03 May 2026 00:00:00 GMTPostpartumHelena Marshhttps://regrowthindex.com/notes/dread-shed/https://regrowthindex.com/notes/dread-shed/On topical minoxidil six weeks in and "nothing's happening"? You're on track. Visible change shows at 4–6 months. Full effect at 12.Sat, 02 May 2026 00:00:00 GMTMinoxidilJames Ardellhttps://regrowthindex.com/notes/female-pattern/https://regrowthindex.com/notes/female-pattern/Is your part widening? Female pattern hair loss is diffuse central thinning with the frontal hairline preserved, the "Christmas tree" pattern.Fri, 01 May 2026 00:00:00 GMTFemale patternHelena Marsh