In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Anti - thyroid drugs , like carbimazole and propylthiouracil ( PTU ) are commonly prescribed for the treatment of hyperthyroidism .
### Output Text:
<span class="chemical">Anti - thyroid drugs</span> , like <span class="chemical">carbimazole</span> and <span class="chemical">propylthiouracil</span> ( <span class="chemical">PTU</span> ) are commonly prescribed for the treatment of hyperthyroidism . 