Background. Psoriasis is a chronic inflammatory skin disease affecting approximately 1–3% of Caucasians. Prolactin has proliferative effects on human keratinocytes, a dominant feature of psoriasis, and it is thought that this hormone may play a role in the pathogenesis of the disease. This study was conducted to confirm or refute these findings in order to better understand the disease pathogenesis. Methods. The subjects were 90 individuals aged between 15 and 47 years. They were divided into three groups of 30 individuals each: psoriatic patients, atopic dermatitis patients, and control group. A questionnaire was filled regarding their demographic and medical history. All of the study subjects underwent venous blood sampling (5？mL), and serum TSH and prolactin levels were checked. Subjects with abnormal TSH were omitted. Results. None of the patients in the study had raised prolactin, and there was no significant difference in the serum prolactin level between patients with psoriasis and atopic dermatitis and the control group. There was no relationship between the severity of psoriasis and serum levels of prolactin. Conclusion. Prolactin does not seem to play a role in the pathogenesis of psoriasis as its serum levels are comparable with atopic dermatitis patients and that of the normal population. 1. Introduction Psoriasis is a chronic inflammatory skin disease affecting approximately 1–3% of Caucasians [1, 2]. The diagnosis of psoriasis is mainly based on its clinical presentation. It is characterized by well-defined red, scaly plaques typically located on the scalp, knee, or elbows [3]. The main pathological features of these skin lesions are keratinocyte hyperproliferation and loss of differentiation, inflammatory cell infiltration, and vascular changes [4, 5]. Complete cure for psoriasis does not exist to date; therefore, treatment is mainly suppressive in nature and is aimed at achieving a period of remission or alleviating the severity of the disease [6]. Considering the proliferative effect of prolactin on human keratinocytes and given the fact that keratinocyte hyperproliferation is a dominant feature of psoriasis, it has been postulated that this hormone may play a role in the pathogenesis of the disease [7]. In a study from Libya, it was demonstrated that serum prolactin levels were significantly higher in patients with mild to moderate psoriasis vulgaris compared to the serum levels of prolactin in patients suffering from atopic dermatitis and those of a control group [8]. On the other hand, atopic dermatitis is also a chronic inflammatory
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