Terminaljuuksed

Terminaljuuksed, or terminal hairs, are the coarse, pigmented hairs that replace thinner vellus hairs in certain areas of the body. They are longer, thicker, and more deeply pigmented than vellus hairs and occur on the scalp, face (more commonly in men), underarms, pubic region, chest, arms, and legs.

Most terminal hairs appear primarily during puberty under the influence of androgens. In androgen-dependent regions, vellus hairs gradually convert to terminal hairs, while in other areas growth patterns are influenced by genetics and hormonal signals. The distribution and density of terminal hairs vary between individuals and between sexes.

Terminal hairs have a relatively long growth, or anagen, phase compared with vellus hairs, contributing to their greater length at full maturity. The duration of the anagen phase differs by body region: scalp terminal hairs can grow for years, whereas body terminal hairs have shorter growth periods and reach shorter final lengths. All terminal hairs cycle through anagen, catagen, and telogen phases, as do other hair types, but the timing and length of these phases differ by site.

Clinically, terminal hair patterns are informative in dermatology and endocrinology. Excess terminal hair growth in women, or hirsutism, can indicate hyperandrogenism or related conditions, such as polycystic ovarian syndrome. Conversely, reduced terminal hair in certain regions can accompany aging or hormonal changes. Differentiating terminal hairs from vellus hairs is relevant for diagnosing hormonal or metabolic disorders and for assessing normal development.