The purpose of this study is to determine the efficacy of treatment with Platelet-rich plasma on Androgenetic alopecia (compared with placebo), between six months and baseline.

Androgenetic alopecia (AGA) is a non-scarring patterned alopecia, multifactorial and a genetic determined skin condition. This pathology is one of the most common forms of progressive hair loss. It's an increasingly frequent complaint of dermatology clinic patients and has a high impact psychologically.

The onset of AGA is gradual and when this pathology progresses, the anagen phase shortens and the telogen phase remains constant. As a result, more hairs are in the telogen phase, and the patient may notice an increase in hair shedding. This area varies from patient to patient and is usually most marked at the vertex in men while women with androgenetic alopecia generally lose hair diffusely over the crown. The incidence and prevalence of AGA increases with age.

Topical minoxidil and oral finasteride are the gold standard therapies for AGA and the only two drugs currently that have US Food and Drug Administration (FDA)-approved indications for the treatment of androgenetic alopecia. Minoxidil and finasteride are known to be effective medical treatments in AGA, especially during the initial grades.

PRP is a plasma concentrate reaped from the patient's whole blood that comprises predominantly platelets. Numerous growth factors (GFs) are present within platelet α granules. Some of the most important of these include platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-β), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), and insulin-like growth factor (IGF). This GFs stimulate cell proliferation and differentiation.

PRP was identified as having a beneficial effect on bone grafting with applications in oral and maxillofacial surgery, orthopedic and cardiac surgery. More recently, increasing interest is seen in the application of PRP in dermatology, for example, tissue regeneration, wound healing such and fat grafting. It has also been shown to promote hair survival and growth, both in vitro and in vivo.

The production of autologous PRP involves extraction of a specific volume of the patient's whole blood, which is then placed in an automated centrifuge to separate the layers of whole blood by their specific weight into 3 separate layers: (1) platelet-poor plasma, (2) platelet-rich plasma and (3) red blood cells.

The patients were divided into two groups (A and B): group A received treatment with PRP on the right half-head and the placebo on the left half-head, whereas group B received treatment with PRP on the left half-head and the placebo on the right half-head.

Inclusion Criteria:

• Patients ≥18 years and < 65 years
• Male patients with a clinical diagnosis of AGA (stage II to V according to the Hamilton-Norwood Scale)
• Female patients with a clinical diagnosis of AGA (stage I to III according to Ludwig Classification)

Exclusion Criteria:

• Patients with other types of alopecia, other than AGA
• Fasting < 3h prior of each injection
• Use of nonsteroidal anti-inflammatory drugs one week before treatment.
• Platelet count < 150 000 μL
• Alterations of coagulation
• Heavy smokers (> 20 cigarettes/day)
• Medications: anticoagulants/ acetylsalicylic acid
• Patient unable to accomplishing all fases of treatment