About androgenetic alopecia
Androgenetic alopecia, or common baldness, is a genetically determined sensitivity of the hair follicle to androgens. It occurs post-pubertally in both males and females and is manifest by the non-scarring loss of hair in the vertex and frontotemporal areas. Terminal hairs are first replaced by thin, small vellus hairs. Eventually the follicles become completely atrophic. Hair loss can begin at any age after puberty and exposure to increased levels of androgens, but onset is highly variable.
With what can androgenetic alopecia be confused?
In men, the diagnosis of androgenetic alopecia is usually obvious. In women, a hormonal abnormality, especially polycystic ovary syndrome (PCOS), should be considered, especially if accompanied by irregular periods, infertility, hirsutism, or acne. Hypothyroidism can also be a cause of thin brittle hair. Other conditions that can cause non-scarring alopecia include: alopecia areata, telogen effluvium, secondary syphilis, hyperthyroidism, anemia, and trichotillomania. Seborrheic dermatitis and tinea infection of the scalp can also cause hair loss.
How is androgenetic alopecia diagnosed?
Hair loss, notably temporal recession in men, is usually first noticed in the third decade of life, but can begin as early as the second decade. It progresses in a distinct pattern, hence its other designation “male pattern baldness”, involving in men the vertex and frontotemporal areas but sparing the posterior and lateral aspects of the scalp. In women, the vertex is involved but the frontotemporal aspect may be spared. Scalp examination reveals replacement of dark terminal hairs with vellus hairs or with atrophic hair follicles; the number of follicles remains unchanged, but they may be difficult to perceive. There is no scarring or inflammation. A family history of baldness is usually present. In most cases, laboratory tests and biopsy are unnecessary. In women, a thyroid stimulating hormone assay and androgen levels, including total testosterone, free testosterone, androstenedione, and DHEA-S should be ordered. If considering polycystic ovary syndrome, follicle stimulating hormone, lutenizing hormone, prolactin levels, and tests of insulin resistance may be appropriate. Iron studies and an ANA test for autoimmune disease may be warranted as well. Severity of androgenetic alopecia is classified in men by the Hamilton classification, and in women by the Ludwig classification.
How is androgenetic alopecia treated?
Oral Minoxidil for androgenetic alopecia
Low dose oral minoxidil is effective in treating hair loss in both men and women. This is an off-label indication for minoxidil. Dosing is very low compared to the dose of minoxidil used for the treatment of high blood pressure (the approved indication for it). Dosing typically starts at 2.5mg per day and can be increased to 5mg day. Side-effects include unwanted hair growth, dizziness and lower leg swelling.
Topical Minoxidil (Rogaine) for androgenetic alopecia
Topical minoxidil (Rogaine), as either a 2% or 5% solution or foam, is moderately effective in stimulating regrowth of terminal hairs on the vertex, and less so in the frontal area. However, treatment must be continued indefinitely for results to be maintained. Minoxidil can be used in women as well.
Finasteride (Propecia) for androgenetic alopecia
Finasteride (Propecia) is a type II 5 alpha-reductase inhibitor that prevents the peripheral conversion of testosterone into the more active dihydrotestosterone. In the clinical trials for Propecia, 83% of men maintained or increased their hair counts after two years of treatment.
Decreased libido and erectile dysfunction have been reported with the use of Finasteride in men. There is also a “post-finasteride syndrome” that has been described, which includes decreased libido, erectile dysfunction, and gynecomastia, in addition to depression and decreased concentration. Not everyone agrees that post-finasteride syndrome exists.
Propecia cannot be used in women of child-bearing age since it is teratogenic, unless proper birth control measures are assured.
Dutasteride for androgenetic alopecia
Dutasteride is a more potent than finasteride as an inhibitor of type I 5 alpha-reductase, and may be more effective in treating hair loss. However, it is not approved for this indication. Several clinical studies support its use, typically at a dose of 0.5 mg daily. The side-effect profile of dutasteride is similar to that of finasteride. It is also contraindicated in women of child bearing age, unless contraception can be assured. Dutasteride mesotherapy is also sometimes used. In this procedure, Dutasteride is injected into the scalp, limiting systemic exposure and possibly reducing the risk of side-effects. Common concentrations used are 0.01%, 0.05%, and 0.005%
Spironolactone for androgenetic alopecia
In women with androgenetic alopecia and elevated androgens, androgen-blocking agents such as spironolactone, flutamide, cimetidine, and cyproterone acetate can be used. These agent block the peripheral effects of testosterone and should not be used in men. The most commonly used medication in this category is spironolactone. Spironolactone is a potassium-sparing diuretic used for treating hypertension. Dosing ranges from 50 mg to 200 mg daily in divided doses. Side-effects with spironolactone include headaches, menstrual irregularities, breast tenderness, and orthostatic hypertension. Although it can elevate potassium, in most cases potassium monitoring is not required. Oral contraception or other methods of birth control is required with spironolactone. Spironolactone is also often used for acne in adult women.
Prostaglandin analogues for androgenetic alopecia
Prostaglandin analogs, such as bimatoprost (Latisse), have come in to use to promote eyelash growth. These drugs are now being investigated in scalp hair loss as well.
Growth factors for androgenetic alopecia
A number of studies support the use of autologous-derived growth factors, but some studies have not confirmed these findings.
Non-pharmaceutical therapies for androgenetic alopecia
Non-pharmaceutical approaches include low-level laser light therapy, various methods of hair transplantation, including punch grafts and scalp reductions, wearing a toupee or wig, or to go bald gracefully (more an option for men than for women).
Low-Level laser light therapy
Low-level laser light therapy delivers light in the 600 to 1000 nm range, at low power of 5 to 500 mW. In some studies these devices have been shown to stimulate hair growth, but other studies have not shown these results. Multiple treatments are required for positive results
Microneedling
Microneedling is sometimes used to stimulate hair growth, presumably by triggering the wound healing response. A roller instrument or stamping instrument can be used with needles in the 0.5 mm to 2.5 mm range. Multiple treatments are required for positive results. Microneedling with minoxidil may be especially helpful, as the microneedling can enhance the penetration of the minoxidil. Similarly microneedling can be used to enhance the penetration of growth factors applied to the scalp.
What is the prognosis for androgenetic alopecia?
The balding process is substantially complete by the age of 50, though additional thinning continues throughout life.
