الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Melasma is a common acquired pigmentary disorder that manifests as symmetric hyperpigmented macules and patches on the face, sometimes neck and rarely forearms, more frequently affecting women of reproductive age. The prevalence of melasma varies between 1.5% and 33.3% depending on the population. The hyperpigmentation in melasma is mainly due to melanocytosis and increased melanogenesis via upregulation of melanin biosynthesis-related genes such as microphthalmia-associated transcription factor (MITF), and tyrosine‐related protein‐1(TYRP1) due to several factors such as genetic predisposition, UV radiation, thyroid disease and pregnancy and drugs such as oral contraceptive pills and phenytoin. Management of melasma is a frustrating experience both for the treating doctors and patients because of its recurrent and often recalcitrant nature. Numerous therapeutic modalities have been tried for this condition such as hydroquinone kojic acid, azelaic acid, arbutin, ascorbic acid, chemical peels, lasers, tranexamic acid, rucinol, oligopeptides, silymarin, orchid extracts, and various botanical extracts with variable success rates. However, TCC remains the gold standard, though associated with significant adverse effects on long-term application. Hence, the quest for an ideal treatment which can achieve effective depigmentation in melasma without any adverse effects has continued. In vitro studies have shown that topical metformin has melanopenic action, which is due to down regulation of the expression of MITF which in turn leads to downregulation of transcription of various melanogenic proteins such as tyrosinase,TRP‐1, TRP‐2, and protein kinase C-beta.