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: Determining testosterone only in cases of low sexual desire or abnormal physical examination would have missed 40 % of the cases with low testosterone , including 37 % of those subsequently improved by androgen therapy .
### Output Text:
Determining <span class="chemical">testosterone</span> only in cases of low sexual desire or abnormal physical examination would have missed 40 % of the cases with low <span class="chemical">testosterone</span> , including 37 % of those subsequently improved by androgen therapy . 