The term androgenetic can be broken down into two terms: Andro and Genetic. "Andro" refers to the androgens (testosterone, dihydrotestosterone) which are necessary to produce male-pattern hair loss (MPHL); while "Genetic" refers to inherited genes which are crucial factors for this type of baldness.

Pathogenesis

Androgens, dihydrotestosterone in particular, play important roles in the development of this pattern of hair loss. Genetic factor could modify the extent to which the hair follicles respond to circulating androgens as well, and this genetically determined disorder takes effect through the gradual conversion of terminal hairs, first into indeterminate hairs, and finally to vellus hairs. Research concluded that the size of the dermal papilla ultimately dictates the size of the growing hair, and in AGA, some dermal papilla cells were lost either by apoptosis, or by cell displacement.

Three Key Features of Androgenetic Alopecia Pathogenesis in men

1. Alteration of hair cycle dynamics

Men with pattern baldness have a reduction in the terminal-to-vellus hair ratio and exhibit a typical distribution of hair loss.

2. Follicular miniaturization

Hair follicles contain androgen receptors. Genes that shorten the anagen phase become active and hair follicles shrink. With successive anagen cycles, the follicles become smaller. This leads to shorter and finer hair and the non-pigmented vellus hairs replace pigmented terminal hairs. All the hairs on the affected area may be involved in the shrinking process and the region may be covered with fine, hardly visible vellus hairs after sometime. Along with hair miniaturization, the production of pigment also ceases.

3. Inflammation

Androgens and Hair Growth

Androgens serve as mediators for terminal hair growth in every part the body and create profound effects on human scalp and body hair. Scalp hair may grow even in the absence of androgens, while body hair growth depends on androgens’ performance. With androgens’ activity, those genetically predisposed develop scalp alopecia, manifested as miniaturization or shrinking of scalp hair follicles in a defined pattern. Androgens cause enlargement of vellus hairs to form terminal follicles in the axilla and pubis in both sexes, on the face, chest and men’s extremities. The seemingly paradoxical effects of androgens on scalp and body hair are still a grey area. Studies about this matter provide greater understanding on molecular mechanisms by which androgens regulate hair growth.

Clinical Symptoms

It is very much easy to recognize the clinical appearance of pattern baldness in most men. The transition from large thick-pigmented terminal hairs to thinner, shorter, indeterminate hairs and finally to non-pigmented vellus hairs in the involved areas take place gradually. Therefore, increase in hair shedding would be noticeable. Androgenetic alopecia takes place in men by gradual thinning in the temporal areas, followed by progressive thinning in the frontal and vertex areas of the scalp. Recession of the frontal hairline is common and frontal and vertex thinning areas may merge, and all the hair all over the crown is lost.

Histopathology

For men with pattern baldness, it is rare to undergo histological diagnosis. However, when the diagnosis on some patients is ambiguous, 4mm punch biopsies are ideally taken from the vertex of the scalp. Two biopsies should be taken - the horizontal and the vertical section.

Terminal anagen hairs are replaced by secondary psuedo-vellus hairs with residual angiofibrotic tracts called follicular streamers or stellae. Vertical sectioned scalp biopsies show a marked reduction in these hairs which normally penetrate through the dermis into the subcutis. Apparently, there is a reduction in the number of follicles.

Horizontal sectioning yields more information on the number and types of follicles which could assist in a more accurate diagnosis. On horizontal sections of scalp biopsies, many pseudo-vellus hair follicles can be identified in the papillary dermis. These indicate that follicles are shrinked rather than destroyed. Pseudo vellus hairs are distinguished from true vellus hairs by the presence of the arrector pili muscle and angiofibrotic streamers.

Others features that may be seen include follicular fibrosis (formation of excess fibrous tissue) which can be seen in around 10% cases, and perifollicular inflammation. These features are non-specific as they maybe commonly seen in some normal scalp.

Management

Normally, treating any kind of hair loss comes in steps - reversal of the hair loss, stabilization of the process, and prevention of the condition. So far, none of the currently available treatments has been proved to be successful in treating pattern baldness. However, there is no life risk in pattern baldness in men that is why it is best to take no treatment at all and allow the balding to progress naturally.

Medical Treatment: The only two treatments that are currently approved by the US Food and Drug Administration for the management of pattern baldness are topical minoxidil and oral finasteride.

Scalp Surgery: This can involve transplants, scalp reduction, rotation flaps, punch grafting, and single follicle transplantation.

Non medical treatment: If patients with mild alopecia do not wish to have medical treatments, they can disguise their baldness by using spray-on scalp dye treatments. These could create an appearance of thicker hair. Patients with advanced alopecia could hide their baldness by wearing quality wigs that appear like natural hair.

Conclusion

Cases of pattern baldness are increasing among men, and many find this condition frustrating. Stem cell scientists, geneticists, developmental biologists and immunologists are continuously working on the progress of hair biology to find effective treatments for the disease.