A family history of androgenetic alopecia, indicating a strong genetic predisposition, significantly increases the risk of developing this disease. The mechanisms of inheritance of male and female baldness have not been fully studied. Hypotheses have been put forward for the participation of various gene loci in the hereditary transmission of androgen alopecia: the androgen receptor gene on the X chromosome, the locus of the insulin-like growth factor -1 gene on chromosome 12, the cytochrome 450c17alpha gene on chromosome 10 and the gene of the enzyme 5a-reductase. Recently, a gene locus associated with male pattern baldness was found on chromosome 20p11.22. Presumably, this gene locus may play a role in the androgen-independent pathway of the disease.
Pathobiology of androgenetic alopecia
Presumably, genetically predisposed hair follicles in the affected areas undergo androgen-dependent gradual replacement of pigmented terminal hair with barely noticeable depigmented downy hair. The process is characterized by a progressive reduction in the duration of subsequent growth phases in the hair cycle, which leads to a decrease in the amount of hair in the anagen phase at a given time and progressive follicular miniaturization, accompanied by the transformation of terminal follicles into vellus-like. As a result, hair loss in the resting phase, or telogen, increases, while the affected follicle produces shorter and thinner hair. In addition, the time between hair loss and their anagenic renewal increases, which leads to a decrease in the amount of hair on the scalp by analogy with involutional alopecia.
With a clearly expressed genetic component, significant progress has been made in understanding the basic elements of the metabolism of the androgens involved. Androgen-dependent processes occur mainly due to the binding of the androgen-independent to the androgen receptor. androgen-independent cell functions are determined by the presence of weak androgens, their transformation into more powerful androgens under the action of 5-alpha-reductase, low enzymatic activity of androgen-deactivating enzymes and the presence of functionally active receptors in large quantities. In the areas of the scalp predisposed to the disease, high levels of androgen-independent and increased expression of receptors were recorded. A key role is assigned to the conversion of testosterone in the dermal papilla, whereas androgen-regulated factors produced by the cells of the dermal papilla presumably affect the growth of other components of the hair follicle.
And although androgen dependence does not belong to the inflammatory type of baldness, early histological changes represent a nonspecific focal perivascular basophilic degeneration in the lower third of the connective tissue membrane, followed by the formation of a weak or moderate near-follicular lymphocytic infiltrate at the level of the sebaceous duct. With further progression of the condition, multinucleated giant cells can form.
With typical manifestations of androgenetic alopecia in men, the frontal-temporal region and the crown are affected. At the same time, men may develop diffuse thinning of the crown while maintaining the frontal growth line, resembling the female type of baldness. In women, there are three clinical models: diffuse thinning of the parietal region while maintaining the frontal hairline; the so-called “Christmas tree” model, which includes diffuse thinning of the central part of the scalp and relative preservation of the frontal hairline; as well as thinning with bitemporal displacement of the frontal hairline, resembling the male type of baldness. Androgenetic alopecia in women can be early, already in adolescence, or late onset, coinciding in time with the menopause period.
Despite the fact that patients with typical baldness periodically experience episodes of hair loss and deterioration, thinning with androgenic alopecia, as a rule, occurs gradually, accelerating with the age of the patient. The degree of final baldness, the age of the onset of the process, the type of baldness are characterized by interindividual variability. In elderly patients, involutional alopecia and typical baldness usually develop simultaneously, and these two different conditions can be difficult to distinguish.
Dermatoscopic signs of androgenetic alopecia are: the difference in the diameters of the hair shaft, the phenomenon of empty follicles, peripilar signs, pigmentation and inflammation of the scalp skin
- The difference in hair diameters is a characteristic diagnostic sign of androgenetic alopecia, affecting more than 20% of hair in androgen-dependent zones. Under the action of androgens, the hair follicles undergo progressive miniaturization, the hair produced gradually becomes thinner and less pigmented. In severe forms of alopecia, miniaturization diffusely affects the follicles, there is a uniform thinning of the hair.
- The phenomenon of empty follicles is characterized by the presence of yellow dots on the scalp, which correspond to empty follicles. The yellow color is due to the fact that the follicular mouths, expanded to a greater or lesser extent, are filled with sebum produced by the sebaceous glands.
- Pigmentation is a non-specific sign of alopecia, however, it is common, especially in severe forms. This is a mesh, cellular pigmentation of the interfollicular epidermis, clearly visible at 40-50-fold magnification. Such dark pigmentation is caused by increased exposure to sunlight on the scalp, which is not sufficiently covered with hair.
- Peripilar signs, also called peripilar rings, look like a dark halo about 1 mm in size around the follicular mouth from which the hair comes out.
- Inflammation: the scalp of patients with androgenetic alopecia is often erythematous, hyperemia may be diffuse or in the form of foci. In most cases, erythema is caused by inflammation caused by seborrheic dermatitis.
We will continue this topic in our next article. And we remind you, if you suffer from androgenetic alopecia and the doctor recommended that you take medications such as finpecia, propecia or any other generic (analog of propecia), then you can buy them online with significant discounts. We wish you good health and see you again in our blog.