Male and female sexual hair patterns differ primarily because of differences in

• A. Estrogen levels
• B. The concentration of circulating androgens
• C. Melanin density
• D. Age

Answer: (B)

Sexual hair patterns are driven by androgens acting on hair follicles. Androgens like testosterone promote the growth of terminal hair in regions that are sensitive to androgens, such as the face, chest, and back. Men typically have higher circulating androgens, which leads to more facial and body hair, while women have lower levels, resulting in finer or less hair in those areas. Estrogen influences the hair growth cycle but does not establish the characteristic male-versus-female distribution. Melanin density affects hair color, not where hair grows, and age can alter overall hair density but does not primarily dictate this sex-based pattern. Thus, the differences arise from the concentration of circulating androgens.