Finasteride increases anagen hair in men with androgenetic alopecia

Abstract

The growth of scalp hair is a cyclical process of successive phases of growth (anagen) and rest (telogen). In previous clinical trials in men with androgenetic alopecia, treatment with finasteride increased scalp hair counts in a defined area (i.e. increased hair density).
The current study used a phototrichogram methodology to assess the effect of finasteride on the phases of the hair growth cycle.
Two hundred and twelve men, age 18-40 years, with androgenetic alopecia were randomized to receive finasteride 1 mg daily or placebo for 48 weeks. At baseline and at 24 and 48 weeks, macrophotographs were taken to measure total and anagen hair count in a 1-cm(2) target area of the scalp.
At baseline, mean total and anagen hair counts in the finasteride group were 200 and 124 hairs, respectively (% anagen = 62%) and the anagen to telogen ratio was 1.74 (geometric mean). In the placebo group, the respective values were 196 and 119 hairs (% anagen = 60%) and 1.57. At week 48, the finasteride group had a net improvement (mean +/- SE) compared with placebo in total and anagen hair counts of 17.3 +/- 2.5 hairs (8.3% +/- 1.4%) and 27.0 +/- 2.9 hairs (26% +/- 3.1%), respectively (P < 0.001). Furthermore, treatment with finasteride resulted in a net improvement in the anagen to telogen ratio of 47% (P < 0.001). In this study, treatment with finasteride 1 mg day(-1) for 48 weeks increased both total and anagen hair counts, and improved the anagen to telogen ratio.
These data provide direct evidence that finasteride 1 mg daily promotes the conversion of hairs into the anagen phase. These data support that finasteride treatment results in favourable effects on hair quality that contribute to the visible improvements in hair growth observed in treated patients.

Full text

British Journal of Dermatology 2000; 143: 804±810.
Finasteride increases anagen hair in men with
androgenetic alopecia
D.VAN NESTE, V.FUH,* P.SANCHEZ-PEDRENO,² E.LOPEZ-BRAN,³ H.WOLFF,§
D.WHITING,¶ J.ROBERTS,** D.KOPERA,²² J-J.STENE,³³ S.CALVIERI,§§ A.TOSTI,¶¶
E.PRENS,*** M.GUARRERA,²²² P.KANOJIA,³³³ W.HE§§§ AND K.D.KAUFMAN³³³
Skin Study Center± Skinterface, Tournai, Belgium
*Department of Clinical Research, Merck Sharpe & Dohme, Hoddesdon, U.K.
²Hospital Virgen de la Arrixaca, Murcia, Spain
³Hospital Clinico San Carlos, Madrid, Spain
§Department of Dermatology, Ludwig-Maximilians-University, Munich, Germany
¶Dallas Associated Dermatologists, Dallas, TX, U.S.A.
**Northwest Cutaneous Research Specialists, Portland, OR, U.S.A.
²²Department of Dermatology, University of Graz, Graz, Austria
³³H.A.I.R. Technology
w
±Skinterface, Brussels, Belgium
§§Universita
Ádegli Studi di Roma, Rome, Italy
¶¶Universita
Ádi Bologna, Bologna, Italy
***Ziekenhuis Walcheren, Vlissingen, Netherlands
²²²Universita
Ádi Genova, Genova, Italy
³³³Department of Clinical Research, Merck Research Laboratories, 126 E. Lincoln Avenue, RY33-500, Rahway, NJ,
07065-0900, U.S.A.
§§§Department of Biostatistics, Merck Research Laboratories, 126 E. Lincoln Avenue, RY33 ±500, Rahway, NJ, U.S.A.
Accepted for publication 4 May 2000
Summary Background The growth of scalp hair is a cyclical process of successive phases of growth (anagen)
and rest (telogen). In previous clinical trials in men with androgenetic alopecia, treatment with
finasteride increased scalp hair counts in a defined area (i.e. increased hair density).
Objectives The current study used a phototrichogram methodology to assess the effect of finasteride
on the phases of the hair growth cycle.
Patients/Methods Two hundred and twelve men, age 18±40 years, with androgenetic alopecia were
randomized to receive finasteride 1 mg daily or placebo for 48 weeks. At baseline and at 24 and
48 weeks, macrophotographs were taken to measure total and anagen hair count in a 1-cm
2
target
area of the scalp.
Results At baseline, mean total and anagen hair counts in the finasteride group were 200 and 124
hairs, respectively (% anagen 62%) and the anagen to telogen ratio was 1´74 (geometric mean).
In the placebo group, the respective values were 196 and 119 hairs (% anagen 60%) and 1´57.
At week 48, the finasteride group had a net improvement (mean ^SE) compared with placebo in
total and anagen hair counts of 17´3 ^2´5 hairs (8´3% ^1´4%) and 27´0 ^2´9 hairs
(26% ^3´1%), respectively (P,0´001). Furthermore, treatment with finasteride resulted in a net
improvement in the anagen to telogen ratio of 47% (P,0´001). In this study, treatment with
finasteride 1 mg day
21
for 48 weeks increased both total and anagen hair counts, and improved
the anagen to telogen ratio.
Conclusions These data provide direct evidence that finasteride 1 mg daily promotes the conversion
of hairs into the anagen phase. These data support that finasteride treatment results in favourable
effects on hair quality that contribute to the visible improvements in hair growth observed in
treated patients.
Key words: androgenetic alopecia, finasteride, increased hair growth, phototrichogram, randomized
double-blind placebo-controlled clinical trial, scalp hair counts
804 q2000 British Association of Dermatologists
Correspondence: Keith D. Kaufman, MD. These data were originally presented at the Annual Meeting of the Society for Investigative Dermatology,
Chicago, IL, U.S.A., 1999.

FINASTERIDE INCREASES ANAGEN HAIR 805
q2000 British Association of Dermatologists, British Journal of Dermatology,143, 804±810
The growth of scalp hair is a cyclical process, made up
of successive phases of growth (anagen) and rest
(telogen).
1
In non-balding scalp, more than 90% of
scalp hair is in anagen.
2,3
However, with androgenetic
alopecia in men (male pattern hair loss) the progressive
shortening of the anagen phase, as well as the increase
in the duration of the lag phase (the interval between
the shedding of a telogen hair and the emergence of a
replacement anagen hair) with successive hair cycles,
cause a progressive decrease in the percentage of hair
follicles in anagen.
3
In men with male pattern hair loss,
only 60±80% of total hair is in anagen.
2,3
This
shortening of the anagen phase leads to progressive
miniaturization of hairs, which contributes to a
decrease of visible hair over affected areas of the
scalp.
4±6
Dihydrotestosterone (DHT), the 5a-reduced metabo-
lite of testosterone, is a key factor in the pathogenesis of
male pattern hair loss in men.
7,8
Finasteride, a specific
inhibitor of the type 2 5a-reductase enzyme, decreases
serum and scalp DHT levels.
9,10
In clinical studies,
finasteride 1 mg day
21
was shown to slow the
progression of hair loss and increase hair growth in
men with male pattern hair loss.
11
Furthermore, with
continued treatment over 2 years, progressive clinical
improvement was observed in patients while hair
density remained stable.
11
These data suggest that
finasteride continued to improve the quality (thickness,
length, growth rate, growth duration and/or pig-
mentation) of hair, perhaps by increasing the number
and duration of hairs in anagen.
The hair count methodology used in previous studies
with finasteride measured the effect of the drug on total
(anagen plus telogen) hair count in a defined area of
the scalp.
11,12
This methodology provided a static
measure of an otherwise dynamic process of hair
growth, stasis and loss, and did not differentiate hairs
that were actively growing (anagen hairs) from those
which were resting and non-growing (telogen hairs).
The quantification of hair growth by a photo-
trichogram technique is a non-invasive method to
provide reproducible serial measures of the number of
hair follicles in the anagen phase relative to the
total hair count, providing dynamic measurements of
the hair growth cycle.
2,3,13
Common to all photo-
trichogram methodologies is the use of two macro-
photographs of a defined region of scalp hair taken a
few days apart. Using this technique, hairs in anagen,
which lengthen by about 0´35 mm day
21
, can be
differentiated from resting, non-growing telogen hairs.
This study is the first using a phototrichogram
methodology to assess the effect of finasteride on the
hair growth cycle in treated subjects.
Methods
Study population
Two hundred and twelve men, 18±40 years of age,
in good physical and mental health, with mild to
moderate vertex balding (IIv, IIIv, IV and V according
to a modified Norwood± Hamilton classification scale)
were randomized to treatment groups.
14,15
One
hundred and seventy-seven patients completed the
48-week study. Exclusion criteria included significant
abnormalities on screening physical examination or
laboratory evaluation, prior surgical correction of scalp
hair loss, use of topical minoxidil within 1 year, use of
drugs with androgenic or antiandrogenic properties,
use of finasteride or other 5a-reductase inhibitors, or
alopecia due to causes other than androgenetic
alopecia. Alterations in hair style or dyeing of the
hair were not allowed during the study.
Study design
This was a randomized, multicentre, double-blind,
placebo-controlled study conducted at 10 investi-
gational sites in Europe and two in the United States.
Institutional review board approval and informed
consent were obtained before patients entered the
study.
After a screening procedure, which included
measurement of total hair count,
12
patients completed
a 2-week, single blind, placebo run-in period. At the
beginning of the placebo run-in period, total and
anagen hair counts were measured 3 days apart.
Anagen hair count was repeated at the end of the
placebo run-in period in order to obtain a mean value
for baseline anagen hair count for each patient
that was the average of two pretreatment measure-
ments. (Because telogen hairs are non-growing, total
hair count measurements, unlike anagen hair count
measurements, could not be repeated within the same
hair growth cycle once the hair had been clipped to the
surface of the scalp.) At the end of the placebo run-in,
patients were randomized to receive finasteride 1 mg or
matching placebo (1 : 1) daily for 48 weeks.
After randomization, patients reported to the clinic
every 12 weeks. Macrophotographs measuring total
and anagen hair counts were taken at baseline and

806 D. VAN NES TE et al.
q2000 British Association of Dermatologists, British Journal of Dermatology,143, 804 ±810
every 24 weeks. Reports of adverse events were
collected throughout the study.
Evaluation procedures
Hair counts. Total and anagen hair counts were
determined from colour macrophotographs of clipped
hair in a 1-cm
2
circular target area at the anterior
leading edge of the vertex balding scalp, centred by a
dot tattoo.
11,12
Hair in the target area was first
clipped to approximately 1 mm length for determi-
nation of the total hair count (Fig. 1a) and then further
clipped to the surface of the scalp in order later to
differentiate growing anagen hairs that lengthen about
0´35 mm day
21
from resting telogen hairs, in the
target area (Fig. 1b). Three days later, a macro-
photograph of the target area was taken for the
determination of anagen hair count, based on
the number of hairs that had lengthened over the
intervening time period (Fig. 1c).
Macrophotographs (Kodak KR-64 35-mm slide film)
were taken using Nikon N-6006 cameras at fixed focus,
distance (primary magnification 1 : 1´4) and exposure
with the use of a Nikon 60 mm f2´8 lens and Canfield
Scientific Inc. (CSI, Fairfield, NJ, U.S.A.) twinflash
mounted on a scalp template. All film was processed
at Qualex Laboratories, Fairlawn, NJ, U.S.A. CSI served
as the central photography centre for quality assurance
and hair counting. At the end of the study, macro-
photographs were enlarged into 8 10 inch
(20´3 25´4 cm) colour transparencies (final magni-
fication, 5´7 : 1)
12
and were converted into dot maps of
each visible hair by trained technicians who were
blinded to patient, treatment and time. Dot maps were
converted into hair counts by means of computer-based
scanners and imaging software.
12
Safety measurements. Safety measurements included
clinical and laboratory evaluations, and adverse event
reports.
Statistical analysis
The baseline anagen hair count was defined as the
mean of the two anagen hair counts obtained at the
beginning and end of the placebo run-in period.
Baseline total hair count was defined as the total hair
count obtained at the beginning of the placebo run-in;
if this value was not available, then the total hair count
obtained just after the screening visit was used. Telogen
hair count was defined as the difference between total
and anagen hair counts. The changes in anagen and
total hair counts were assessed by the differences
between the counts at week 48 and baseline, and the
mean values for each treatment group were determined
using the SASe(SAS Institute Inc., Cary, NC, U.S.A.)
Least Squares Mean program. The percentage of hairs
in anagen (percentage anagen) at week 48 was
compared with the percentage of hairs in anagen at
baseline. The ratio of anagen to telogen hair count
(anagen to telogen ratio), which was first calculated as
the ratio for each patient and then summarized over
the entire patient sample, was compared at week 48
with the ratio at baseline.
Hypothesis testing for anagen and total hair counts,
percentage anagen and anagen to telogen ratio was
performed using analysis of variance (anova). The
treatment effect for each measure was assessed based
Figure 1. Phototrichogram methodology. Macrophotographs of a 1-cm
2
representative area of the balding scalp, centred by a dot tattoo. (a)
Macrophotograph of target area for total hair count. (b) Macrophotograph of target area after hairs were further clipped to the surface of the scalp.
(c) Three days later, macrophotograph of the target area for anagen hair count.

FINASTERIDE INCREASES ANAGEN HAIR 807
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on the intention-to-treat principle, i.e. analysis
included all men who had both baseline and at least
one on-treatment measurement. Missing data were
imputed by carrying forward the last on-treatment
observation from the previous time point.
All efficacy analyses were corroborated with a non-
parametric Cochran±Mantel±Haenszel (CMH) test. For
all the efficacy analyses except for the anagen to
telogen ratio, the CMH test yielded similar results to
anova. For the anagen to telogen ratio, the ratio in log
scales satisfied the assumptions of homogeneity of
variance and normality of distribution. Therefore,
analysis of variance was performed on the log of the
on-treatment to baseline anagen to telogen ratio (or
change from baseline in log scale), and the geometric
mean ratios are presented.
The focus of the safety analyses was on the
biochemical measures, using anova, and on adverse
event reports. The between-group comparison of the
proportion of patients with an adverse event was done
using Fisher's exact test.
Results
Baseline characteristics
Two hundred and twelve men with active mild to
moderate hair loss in the vertex area enrolled in the
study. The two treatment groups were generally similar
in terms of baseline characteristics (Table 1), although
slightly more patients were classified as II vertex or
IV hair loss pattern in the finasteride group, while
slightly more patients were classified as III vertex or
V in the placebo group. Ninety (85%) finasteride-
treated subjects and 87 (82%) placebo-treated subjects
completed the 48-week study.
Hair count
Total hair count. Mean total hair counts at baseline and
week 48 are listed in Table 2. At week 48, patients on
finasteride had a mean increase of 7´2 hairs (95% CI:
3´7± 10´7) in the 1 cm
2
circular target area, while
patients on placebo had a mean decrease of 210´1
hairs (95% CI: 213´6 to 26´7). Thus, treatment with
finasteride for 48 weeks led to a net improvement
(mean ^SE) in total hair count of 17´3 ^2´5 hairs
(8´3% ^1´4%) in the target area compared with
placebo (P,0´001, Fig. 2a).
Anagen hair count. Mean anagen hair counts at baseline
and week 48 are listed in Table 2. Finasteride treatment
led to a progressive increase in mean anagen hair
count over 48 weeks (P,0´001, Fig. 2b), while
treatment with placebo led to a decrease in mean
anagen hair count (P,0´001, Fig. 2b). At week 48,
patients on finasteride had a mean increase of 18´0
anagen hairs (95% CI: 13´9±22´0), while patients on
placebo had a mean decrease of 29´0 anagen hairs
(95% CI: 213´1 to 24´9). Thus, treatment with
finasteride for 48 weeks led to a net improvement in
anagen hair count of 27 ^2´9 hairs (26% ^3´1%) in
the target area compared with placebo (P,0´001).
Furthermore, the difference between the treatment
groups increased between week 24 and week 48
(P0´02). The percentage of hairs in anagen (i.e.
percentage anagen) increased from 62% at baseline to
68% at week 48 in the finasteride group, while it
decreased from 60% at baseline to 58% at week 48 in
the placebo group, resulting in a net improvement
of 8% in percentage anagen hair with finasteride
compared with placebo (P,0´001).
Tabl e 1. Baseline characteristics of men randomized
Finasteride 1 mg (n106) Placebo (n106)
Age (mean ^SE) 30´2 ^0´6 29´3 ^0´6
Age at which hair loss began (mean ^SE) 23´7 ^0´5 22´6 ^0´5
Number (%) of patients with family history
a
74 (70) 71 (67)
Baseline hair count (mean ^SE)
b
Total 198 ^5 197 ^5
Anagen 124 ^5 119 ^5
% Anagen 62 ^260^2
Anagen/telogen ratio 1´74 ^0´15 1´57 ^0´13
Number (%) of patients with hair loss pattern
c
Grade II vertex 40 (38) 35 (33)
Grade III vertex 25 (24) 35 (33)
Grade IV 29 (27) 18 (17)
Grade V 12 (11) 18 (17)
a
Family history Parents or siblings with male pattern hair loss.
b
Measured in a 1-
cm2
circle.
c
According to a modified Norwood±Hamilton
Scale.

808 D. VAN NES TE et al.
q2000 British Association of Dermatologists, British Journal of Dermatology,143, 804 ±810
Anagen to telogen ratio. Anagen to telogen ratios at
baseline and week 48 are listed in Table 2. For the
finasteride group, there was improvement in the
anagen to telogen ratio (P,0´001 at week 48),
whereas treatment with placebo resulted in a decrease
in the ratio that approached statistical significance
(P0´06 at week 48) (Fig. 2c). At week 48, patients
on finasteride had an increase in the anagen to telogen
ratio of 33% (geometric mean; 95% CI: 21±47%),
compared with patients on placebo who had a mean
decrease of 29% (95% CI: 218% to 0%). This resulted
in a net improvement in the anagen to telogen ratio of
47% for finasteride at 48 weeks compared with placebo
(95% CI: 27± 68%; P,0´001). Furthermore, the
difference between the treatment groups increased
between week 24 and week 48 (P0´023).
Adverse events
Treatment with finasteride was generally well-
tolerated. The incidence of drug-related adverse events
was similar in the finasteride and placebo groups, and
no patients discontinued the study due to an adverse
event related to treatment with finasteride. In previous
large clinical trials with finasteride 1 mg,
11
a few
patients experienced reversible impairment of sexual
function; no other adverse effects of finasteride were
observed. In this study, drug-related sexual adverse
events occurred in two patients (1´9%) in the
finasteride group and in one patient (0´9%) in the
placebo group. Of the two finasteride patients, one
reported resolution of the adverse event while on
therapy, whereas the other reported resolution of the
adverse event 2 weeks after completion of therapy.
Discussion
Treatment with finasteride 1 mg day
21
has been
demonstrated to improve scalp hair growth in men
with male pattern hair loss,
11
confirming that DHT is a
Figure 2. Hair count. Mean change (^SE) from baseline in (a) total
hair count and (b) anagen hair count; (c) mean percentage change
(^95% confidence interval) from baseline in the anagen to telogen
ratio.
Tabl e 2. Hair count data (mean ^SE)
Finasteride 1 mg (n93) Placebo (n91)
Baseline Week 48 Baseline Week 48
Total hair count 200´0 ^5´2 207´4 ^5´4 195´8 ^5´4 186´2 ^5´0
Anagen hair count 124´4 ^4´9 142´5 ^5´4 119´0 ^4´6 110´2 ^4´7
Telogen hair count
a
75´1 ^4´0 64´2 ^3´3 76´8 ^3´5 76´0 ^3´5
Anagen/telogen ratio
b
1´74 ^0´15 2´33 ^0´20 1´57 ^0´13 1´43 ^0´13
a
Telogen hair count (Total hair count) 2(Anagen hair count).
b
Anagen/telogen ratio Geometric mean (anagen hair count/telogen hair
count).

FINASTERIDE INCREASES ANAGEN HAIR 809
q2000 British Association of Dermatologists, British Journal of Dermatology,143, 804±810
key factor in the pathophysiology of androgenetic
alopecia in men. The current study furthers our
understanding of the pathophysiology of male pattern
hair loss and the effect of DHT suppression with
finasteride on the hair growth cycle in men with this
condition.
In this study, finasteride treatment increased the
amount and percentage of anagen hair and improved
the anagen to telogen ratio in men with male pattern
hair loss. Anagen hair count, first measured at
24 weeks, increased progressively over 48 weeks for
finasteride-treated subjects. In contrast, placebo-treated
subjects lost anagen hair during the study, consistent
with the progressive shortening of the anagen phase
duration that leads to the hallmark of androgenetic
alopecia, follicular miniaturization. By 48 weeks, treat-
ment with finasteride had resulted in a 26% net
improvement in anagen hairs compared with placebo.
This increase in anagen hair count, together with the
increase in the anagen to telogen ratio, is direct
evidence that treatment with finasteride promotes the
conversion of hair follicles into the anagen phase.
While the duration of the anagen phase decreases
between successive growth cycles in male pattern hair
loss, the length of the lag phase also increases,
contributing to the rate of apparent hair loss.
3
Thus,
the increase in the anagen hair count observed with
finasteride treatment could be due to the reversal of
both of these processes. A more precise characterization
of the effect of finasteride on the duration of the specific
phases of the hair growth cycle would require that
individual hair follicles be followed over successive
cycles and the length of each phase measured.
3
Regardless, the results of this study confirm that
finasteride treatment increases total hair count by
increasing actively growing anagen hair.
The ratio of anagen to telogen hairs was also shown
to increase progressively over 48 weeks of finasteride
treatment. The increase in the anagen to telogen ratio
with finasteride treatment at 24 weeks reflected
primarily the changes in anagen hair count, as telogen
hair count had not significantly changed from baseline.
As the duration of the telogen phase is not altered in
male pattern hair loss,
3
finasteride treatment is not
likely to affect this phase directly. Rather, as anagen
phase is prolonged, fewer hairs are in telogen. Thus,
the telogen hair count would be expected eventually
to decrease with finasteride, due to continued pro-
longation of the anagen phase. This is consistent with
the observation that, in this study, the reduction in
the telogen hair count, and its favourable effect on the
anagen to telogen ratio, followed the increase in the
anagen hair count with finasteride. These positive
changes in the hair cycle, associated with the
progressive improvement in scalp coverage observed
in treated subjects, imply favourable consequences on
clinically important aspects of hair quality (thickness,
length, growth rate, growth duration and/or
pigmentation) in men on treatment.
As in men, similar hair growth cycle abnor-
malities are observed in women with androgenetic
alopecia.
16,17
However, results from a placebo-
controlled study of postmenopausal women with
androgenetic alopecia demonstrated no benefit of
finasteride after 1 year.
18
This difference in treatment
efficacy between men and women may be due to
gender differences in the role of type 2 5a-reductase in
the pathophysiology of androgenetic alopecia. Despite
this, use of a type 2 5a-reductase inhibitor such
as finasteride is contraindicated in women during
pregnancy due to the potential risk of undervirilization
of a male fetus.
19
In conclusion, the results of this study confirm that
in men with male pattern hair loss, treatment with
finasteride 1 mg day
21
favourably affects the hair
growth cycle by promoting hair follicles into the
anagen phase. Anagen hair count and the anagen to
telogen ratio increased progressively with continued
treatment with finasteride over the duration of the
48-week study. In contrast, these parameters decreased
with placebo treatment, consistent with the progressive
follicular miniaturization that is the hallmark of male
pattern hair loss. Finasteride 1 mg day
21
was generally
well tolerated by men in this study and adverse events
related to therapy with finasteride were minimal.
Acknowledgments
This clinical study was entirely supported by Merck
Research Laboratories, Merck & Co., Inc. Merck & Co.,
Inc. is the company that manufactures and markets
finasteride.
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