This pilot study evaluates the efficacy, safety, and tolerability of topical latanoprost acid in adult women with female pattern hair loss, with a minority of participants diagnosed with chronic telogen effluvium. In this randomized, double-blind, single-center, dose-ranging trial, participants receive latanoprost acid 0.01%, 0.05%, or 0.1% applied once daily for 6 months; a small vehicle group is included to support masking and assess tolerability. The primary outcome is the within-participant change in target-area hair count (hairs/cm²) from baseline to Month 6. Secondary and exploratory outcomes include follicular-unit distribution (percent of 1-, 2-, and 3-hair units), number of yellow dots, and patient-reported outcomes.

Detailed Description This single-center, randomized, double-blind, vehicle-controlled, dose-ranging pilot trial evaluated topical latanoprost acid in adult women with diffuse scalp hair loss consistent with female pattern hair loss (FPHL) or chronic telogen effluvium. Eligible participants were women aged 18-60 years with FPHL classified as Ludwig I-III or with chronic telogen effluvium. Key exclusion criteria included recent use of hair-growth treatments, active scalp dermatoses, or significant uncontrolled medical conditions. Forty participants were screened and 29 were enrolled.

Randomization and masking Participants were randomly assigned to one of four groups: vehicle (placebo) or latanoprost acid 0.01%, 0.05%, or 0.1%. Randomization was computer-generated. Allocation concealment was maintained using identical-appearance dropper bottles labeled with code numbers. Both participants and investigators were blinded to treatment assignment through Month 6, including during all outcome assessments. The placebo formulation consisted of the same vehicle without active latanoprost acid to ensure a comparable application experience across groups.

Intervention and study conduct Participants applied the assigned topical solution once daily for 6 months to the androgen-dependent scalp area affected by thinning. Participants were instructed to distribute the solution evenly using the dropper (2-3 mL per application as per instructions), avoid runoff, and refrain from washing the treated area for at least 8 hours after application. Usual hair-care routines (eg, shampoo and styling products) were kept constant during the study. Concomitant hair-loss therapies were prohibited throughout the treatment period.

Efficacy assessments and procedures Standardized clinical photography and trichoscopy were obtained at study visits, including baseline and follow-up assessments at Months 3 and 6. Outcome measurements were performed at standardized points within the treated region. A standardized 1 cm2 assessment field within the treated area was used to support consistent, repeatable measurements across visits. All visible hairs within the assessment field were counted to determine target-area hair count (TAHC, hairs/cm2). Trichoscopic outcomes included follicular-unit (FU) arrangement reported as the percentage of follicular units with a single hair (%FU1) and with 2 and 3 hairs (%FU2 and %FU3), as well as the number of yellow dots. Hair-shaft thickness was assessed on a 0-3 grading scale. Patient self-assessments were collected at Months 3 and 6 using a structured questionnaire addressing shedding, hair thickness/volume, and overall growth/satisfaction.

Endpoints: The prespecified primary endpoint was the within-subject absolute change in target-area hair count (ΔTAHC, hairs/cm^2) from baseline to Month 6 within the standardized assessment field. Secondary endpoints included change from baseline to Month 6 in hair-shaft thickness grade, follicular-unit (FU) arrangement (%FU1, %FU2, %FU3), and patient-reported outcomes collected using a structured questionnaire. Exploratory endpoints included dermoscopic markers, in particular change from baseline in the number of yellow dots assessed at Months 3 and 6.

Safety and tolerability Safety and tolerability were assessed at each visit through systematic adverse event collection, targeted scalp examination (including evaluation for erythema and irritation), and measurement of vital signs. Safety monitoring covered local scalp findings and any systemic effects during the 6-month treatment period.

Inclusion Criteria

• Female participants aged 18-60 years
• Diffuse scalp hair loss consistent with female pattern hair loss (FPHL), Ludwig grade I-III, or chronic telogen effluvium
• Willingness to comply with all study procedures

Exclusion Criteria

• Recent use of other hair-growth treatments
• Active dermatologic conditions affecting the scalp (active scalp dermatoses)
• Significant uncontrolled medical conditions

Eligible participants were self-identified women aged 18-60 years.

Individual participant data (IPD) will not be shared with other researchers. IPD will not be made available to protect participant privacy and confidentiality and due to the small sample size, which may increase the risk of re-identification. Only aggregate, de-identified results will be reported.

Double-blind masking was maintained by dispensing study product in identical-appearance dropper bottles. Each bottle carried a coded sticker label on the packaging, and treatment allocation was concealed by the code. Participants and investigators remained blinded through Month 6. The vehicle contained the same formulation without latanoprost acid to support masking.