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The distribution of pubic hair has long been regarded as a secondary sex character. Attention has been directed especially to the upper border of the pubes; a horizontal line of termination has come to be regarded as feminine, one that pointed towards the umbilicus as masculine. Exceptions of this rule have been found regularly. A more extensive investigation of this subject, utilizing an adequate sample of the population, therefore, is of obvious value.

The pubic hair pattern was studied in photographs of 400 men and 400 women. For convenience of presentation they have been divided into age groups by decades. Although all of these groups are selected, for the purpose of the present investigation, they may be considered as a valid sample of the general population. Volunteers with diseases, which were considered to have a possible influence on hair growth, were excluded. 80 pregnant women formed an additional series.*

Preliminary examination of this material showed that the distribution of pubic hair can be classified for practical purposes into four fundamental types, illustrated in Fig. 1. The first, or horizontal type, is characterized by terminating superiorly in a horizontal line. This corresponds to the classical feminine distribution. The second, or sagittal type, resembles the first except, for an additional linear upward extension in the mid-line, ranging from a few scattered hairs, a definite streak of hairs confined to this line, to a thin band of hair arranged on either side of this line. The third, or acuminate type, corresponds to the classical masculine distribution, the upward extension being triangular in shape (inverted V-shaped), pointing towards the umbilicus. In the fourth, or disperse type, hair is distributed over the abdomen without forming a discrete geometrical pattern.

This classification is concerned with the character of the upper border of the pubic hair. There are numerous other features, such as the luxuriance of hair development, differential distribution in the genital region and degree of extension on to the thigh, which are of interest. Their inclusion in the present study would lead to undue complication.

In addition to the classification of pubic hair pattern, approximate quantitative estimates were made of the degree of hirsutism exhibited by the anterior aspect of the thigh and the chest for all men. In the original observations, the amount of hair was recorded in three categories; sparse, moderate and dense. In order to simplify the presentation, the moderate and dense categories have been combined into one, which is termed conspicuous. The age groups have been summarized into two major groups; the 15 - 24 age group, and the combination of the age groups ranging from 25 - 64.

As a necessary preliminary to an investigation into the clinical significance of excessive hair growth in women, observations were made of the normal variability of facial hair growth of upper lip and chin in all women. Four grades of hair growth were distinguished at each of the two sites. Minor degrees of hair growth constituted the grades 1 and 2. More servere degrees were placed in grades 3 and 4.

Fig. 1
Four fundamental types of pubic hair distribution,
determined by the pattern of upward extension of hair from the basic triangle.

Discussion

The frequency with which the various Types of pubic hair distribution occurred in our series, is summarized in Table 1. The horizontal type of pubic hair distribution, found in the 15 - 24 age group, is surprisingly high. At this age 38.6 per cent of the men have a horizontal pubic pattern, while 49.1 per cent show the acuminate type. Under these circumstances it is scarcely appropriate to call the horizontal pattern "feminine" and the acuminate "masculine." In the older age groups of men, there is a decrease in the horizontal type from 17, 7 per cent to 8 per cent, the acuminate type remaining approximately constant. It is particularly interesting to note, that in the 25 - 64 age groups the disperse pattern appears in 27 per cent of the cases. This pattern is characterized by general hairiness of the suprapubic region and its appearance is correlated with general increase in hirsutism with age.

The correlation between the upward extension of pubic hair and the development of chest and thigh hair is apparent from the data presented in Table 2. In the 15 - 24 age group 46 per cent of the men with sparse chest hair have a horizontal pattern of pubic hair, while only 5 per cent of the individuals with conspicuous chest hair show this pubic pattern. The corresponding for the older age group are 35 per cent and 3 per cent. Of the men in the 15 - 24 age group, who have only sparse hairiness of the thigh 79 per cent exhibit the horizontal pubic pattern, compared with 28 per cent in the men with conspicuous thigh hairiness. The older men yield corresponding figures of 41 per cent and 4 per cent respectively.

General hirsutism is consequently an important, but not the only, factor determining pubic hair distribution. The tendency towards general development of hair exhibits itself earlier on the thigh than on the chest. Conspicuous thigh hair is presented in 81 per cent of the 15 - 24 age group and 77 per cent of our series of older men, but only 20 per cent of the 15 - 24 age group had conspicuous chest hair, compared with 70 per cent of the older group.

In contrast to the men, the pubic hair distribution in the women is preponderantly of the horizontal type. (The percentage presenting the different degrees of growth becoming progressively smaller the more extensive is the growth.) The incidence of the acuminate type is with 17.1 per cent highest in the 15 - 24 age group, remains approximately constant in the 25 - 44 age groups then suddenly falls in the 45 - 64 age group, to only one person. It is significant, that the acuminate pattern is found in 13.8 per cent of pregnant women. There is consequently no indication of a correlation between fertility and pubic hair pattern. This again emphasizes the inadvisability of using the term "masculine" for the acuminate type of hair distribution. An extensive previous investigation on hair growth in women is that of Fink [1]. His findings for the acuminate and sagittal pattern of hair growth are lower than the obtained here, whereas our results are in fundamental agreement with the da ta of Rodecurt [2], who demonstrated that a substantial proportion of women show a degree of hair growth, that departs from the "feminine" distribution. Studies on the development of pubic hair (Priesel and Wagner [3], Greulich [4]) also have shown, that the horizontal type appears in both sexes at puberty.

It may consequently be regarded as the basic pattern, from which the other types develop by upward extension. The retention of the horizontal distribution as the definitive type in most adult women, seems to be a result of general feminine characteristic of paucity of body hair, rather than of a special factor affecting the pubic region. In other words, it follows that body hair growth in both sexes should be thought of in terms of degree, rather than of distribution.

The degree of facial and abdominal hair growth shows considerable variation with age and hence it is important for such changes to be taken into consideration in any study on the correlation between hair growth and other physical characteristics. In Table 3 are given the relative incidences of minor (1 - 2) and major (3 - 4) degrees of hair growth on lip and chin in correlation to the pubic pattern, by decades. The variation with age in the incidence of the latter at these sites is shown graphically in Fig. 2.

No systematic correlation between abdominal and facial hair growth and general body hair was attempted in the present investigation, but a strong impression was gained, that the heavier degrees of general hirsuties in younger women are found in those, presenting the major grades of facial hirsuties, combined with the acuminate pubic pattern.

Observations on hair growth in the older age groups in women are scanty. Our findings with respect to facial hair growth differ somewhat from those, obtained by Trotter[5], who found that the incidence of facial hypertrichosis gradually increased from youth to old age, without a conspicuous change at any particular period.

Pubic hair distribution has been examined in photographs of 400 men and 480 women. The classical division into "masculine" and "feminine" types is found to be unsatisfactory. An adequate classification recognizes four types, designated as horizontal, sagittal, acuminate and disperse. The acuminate or "masculine" type is present in 55 per cent of the men and 8 per cent of the women. It is also the basic type for male adolescents, is characteristic of 39 per cent of the 15 - 24 age group and persists in 12 per cent of the adult males. In males the decrease in frequency of the horizontal pattern with age is associated with increase in general hirsutism and is accompanied by the development of a disperse pubic hair pattern.

In the younger age groups (15 - 34) of women, the existence of a substantial proportion of individuals who depart from what is ordinarily considered to be "feminine" pattern of hair growth is confirmed. It is likely that the difference in body hair growth between males and females are a matter of degree rather than a reflection of a more fundamental difference in hair distribution. After the fifth decade, there is a striking increase in the incidence of facial hirsuties and, at the same time, a reduction in the degree of pubic hair growth.

* The author wishes to express his appreciation for the parts of this material, which was so kindly put at his disposal by Prof. Bogdan Chazan of the National Research Institute of Mother and Child in Warsaw.

Literature cited

Sample Photos from Study
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