Provided is a heterocyclic devivatives exhibiting an action of thyroid hormone β receptor agonist, and being effective in prophylaxis and treatment of diseases involved with the above action. Namely, this invention provides a compound represented by gemeral formula [I] or pharmaceutically acceptable salts thereof, and a medicament comprising the same as effective ingredient.(wherein, the symbols are as defined in the specification.)本發明提供顯示甲狀腺荷爾蒙β受體作動作用，而對預防或治療該作用參予的疾病有效之雜環衍生物。亦即提供通式[I]表示的化合物或其藥理學上容許的鹽，以及含有該化合物作為有效成分的醫藥。(式中，各記號如說明書中所定義)
