Thyroid fluctuations can indeed trigger melasma. Since your skin is dry and sensitive, and you cannot tolerate hydroquinone, there are gentler, highly effective options. I recommend topical azelaic acid, which brightens the skin while calming sensitivity. Other excellent, non-irritating alternatives include niacinamide, kojic acid, and vitamin C, which help fade pigmentation gently. For a stronger approach, your dermatologist might suggest prescription-strength topical cysteamine or low-dose oral tranexamic acid. Crucially, protect your sensitive skin daily with a mineral-based sunscreen (using zinc oxide or titanium dioxide) to prevent the melasma from darkening. Please consult your doctor before starting any new treatment.