Androgenetic alopecia is a common form of diffuse hair loss in both men and women,It primarily affects the top and front of the scalp with different clinical presentations and there are numerous classification systems for grading purposes.

These systems vary from the simple systems based on recession of the hairline to more advanced multifactorial systems based on morphological and dynamic parameters that affect the scalp and hair. Most of these systems have certain limitations. Currently, the most commonly used are Hamilton- Norwood classification system for males where there are two areas of hair loss that gradually enlarge to produce recession at the temples and thinning in the crown. These regions coalesce until the entire front, top and crown (vertex) of the scalp are bald(2 major pattern,7 grades) and the Ludwig system for females which classify the Female Pattern Hair Loss into three grades depending on the reduction in hair density over the crown and frontal scalp with retention of the frontal hairline.

Etiopathogenesis of Androgenetic Alopecia has not yet been fully elucidated. Genetic factors, hair follicle cycle abnormalities, aging process and androgen dependent process including end organ sensitivity have been all incriminated as etiological factors .

Dermoscopy has emerged as an useful tool in the diagnosis of hair loss disorder including Androgenetic Alopecia. Important features of Androgenetic Alopecia on Dermoscopy include hair shaft thickness heterogeneity, yellow dots (irregularly distributed and with a remarkable variability in size and shape), perifollicular discolouration (the peripilar sign), an increased proportion of thin and vellus hairs (>10 % of the hairs) and a large number of follicular units with only one emerging hair shaft. Thin wavy hair and honeycomb hyperpigmentation often coexist as additional, nonspecific features Vitamin D is a secosteroid hormone that plays an important role in calcium homeostasis and bone health. It has three sources: endogenous synthesis in the skin, which is induced by Ultraviolet B radiation; dietary intake; and supplementation .

Basically, Vitamin D is a modulator of both innate and adaptive immune systems through its various effects on T and B lymphocytes, dendritic cells and macrophages. There is a well-established causal connection between vitamin D deficiency and some autoimmune diseases , and possible association with some hair disorders, as it has been demonstrated that vitamin D receptors are strongly expressed in hair follicles and keratinocytes. Such an expression was found to be necessary for maintenance of the normal hair cycle. Also, it has also been shown that lack of vitamin D receptors reduces epidermal differentiation and hair follicle growth, and that an optimum concentration of Vitamin D3 is essential to delay aging and hair loss.

Several studies were done to evaluate the role of vitamin D in different hair disorders with contrasting results. Some studies revealed low serum levels of Vitamin D in women with chronic telogen effluvium,Female Pattern Hair Loss and Alopecia Areata.While, two studies showed no correlation between the extent and severity of male androgenetic alopecia with serum Vitamin D3 level.

Based on the above contrasting reports, we sought to evaluate the levels of Vitamin D in patients with androgenetic alopecia in order to establish its possible role in the etiopathogenesis and hence in the treatment of such a common and chronic hair disorder

Inclusion Criteria:

• The study will include 60 patients with androgenetic alopecia (30 males & 30 females) and 30 age and sex-matched healthy volunteers.

Exclusion Criteria:

- 1-Patients with a history of topical or systemic treatment within the last month.

2-Patients with a history of concomitant skin or systemic disease. 3- Pregnant or lactating women. 4- Smokers. 5- Patients receiving phototherapy within 6 months

The study will include 60 patients with androgenetic alopecia (30 males & 30 females) and 30 age and sex-matched healthy volunteers. Study subjects will be recruited from the Dermatology Outpatients' Clinic, Assiut University Hospitals, Assiut, Egypt. Informed consent will be obtained from all subjects