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: METHODS : Retrospective review of medical records of 236 patients with hyperthyroidism admitted in our department ( in - or out - patients ) from 1986 to 1992 .
### Output Text:
METHODS : Retrospective review of medical records of 236 patients with hyperthyroidism admitted in our department ( in - or out - patients ) from 1986 to 1992 . 