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: We documented airway occlusion during sleep and an abnormally high supraglottic resistance while awake in a 54 - yr - old woman who had developed physical changes and the syndrome of obstructive sleep apnea while being administered exogenous androgens .
### Output Text:
We documented airway occlusion during sleep and an abnormally high supraglottic resistance while awake in a 54 - yr - old woman who had developed physical changes and the syndrome of obstructive sleep apnea while being administered exogenous <span class="chemical">androgens</span> . 