The effect of finasteride and distribution of androgens on different parts of the scalp:
ORIGINAL ARTICLE
Evaluation of androgens in the scalp hair and plasma of patients with male-pattern baldness before and after finasteride administration
H.K. Ryu*†, K.M. Kim*, E.A. Yoo†, W.Y. Sim‡ and B.C. Chung*
Summary
Background Finasteride, a competitive inhibitor of the enzyme 5α-reductase II, is widely used as a medical treatment for patients with male-pattern baldness (male pattern baldness), which is affected by the distribution of androgenic steroids. It is also notable that the androgenic effect in male pattern baldness is different for each region of the head.
Objectives To study the effect of the drug finasteride, we quantified androgenic steroids in the vertex and occipital scalp hair and in the plasma of patients with male pattern baldness.
Methods The patients with male pattern baldness, aged 23–52 years, were treated with finasteride 1 mg daily for 5 months. The hair and plasma samples were hydrolysed, extracted with n-pentane, and derivatized with MSTFA : NH4I : DTE (1000 : 4 : 5, v/w/w). We analysed the concentrations of dihydrotestosterone (DHT) and testosterone (T) in the hair and plasma using gas chromatography–mass spectrometry (GC-MS).
Results In the hair, the ratio of DHT/T was decreased in the vertex scalp hair after the individual received finasteride (P < 0·005). However, we found no significant difference in the ratio of DHT/T in the occipital scalp hair before and after individuals received finasteride. Like the results in the vertex scalp hair, the ratio of DHT/T in the plasma was remarkably decreased after finasteride administration (P < 0·001).
Conclusions This study supports the effect of finasteride in patients with male pattern baldness by examining the decreased level of DHT/T in scalp hair and in plasma. Thus, in view of the androgenic effect in the different hair regions, the vertex scalp hair plays a more important role for patients with male pattern baldness treated with finasteride than does the occipital hair.
It has long been assumed with male-pattern baldness (male pattern baldness) that the terminal hair follicle is miniaturized and then miniaturized hair follicles produce shorter and thinner hair.1 male pattern baldness is inheritable and strongly androgenic dependent.2 Among the androgen hormones, dihydrotestosterone (DHT) plays a definite role in male pattern baldness.3 Namely, DHT is converted from testosterone (T) by 5α-reductase in most target organs. The enzyme 5α-reductase has been identified as being of two types in humans. 5α-reductase type I is the predominant enzyme in the skin and liver, whereas type II exists in hair follicles, in the prostate and the liver,4,5 and affects male pattern baldness. Generally, DHT competes with T to bind with the androgen receptor, and the affinity of DHT is fivefold more potent than T.6,7 Finasteride is one of the most commonly used drugs for treating male pattern baldness.8 As a competitive inhibitor of the enzyme 5α-reductase II,8,9 finasteride lacks an affinity for the androgen receptor9 and decreases the DHT level in scalp skin and in serum.10,11 In previous studies of the effects of finasteride, the amount and percentage of anagen (the growth phase) hair increased in the male pattern baldness group treated with finasteride.12 In addition, finasteride significantly affected the individuals who received the treatment. Finasteride increased hair weight, increased follicle length10 in Macaque monkeys and hair count,4,13 and increased hair growth in humans.14 It is also notable that the individual regions of the hair have different properties. The outer root sheaths of the frontal hair follicles have higher levels of androgen receptors than do the occipital follicles. By comparing the frontal hair follicles with the occipital hair follicles in male pattern baldness, we found that the level of 5α-reductase II is increased nearly three times in the frontal hair follicles.15 In addition, the distribution of androgenic steroids is different in the various regions of the hair of individual subjects. Generally, male pattern baldness is affected by the distribution of androgenic steroids in the vertex scalp hair.16 Based on our previous report, we supposed that the effect of finasteride is different between vertex and occipital scalp hair. In 2004, our laboratory studied the levels of DHT, T and epitestosterone in the hair and plasma of individuals with premature male pattern baldness and in the control group.16
