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: rhIGF - I treatment reduced the steady state renal IGF - I mRNA level but did not modify gene expression of the IGF - I or GH receptors .
### Output Text:
rhIGF - I treatment reduced the steady state renal IGF - I mRNA level but did not modify gene expression of the IGF - I or GH receptors . 